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A study of the taxonomy and some aspects of the ecology of marine ostracods in the plankton of Indian… McHardy, Robert Alexander 1961

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A STUDY OF THE TAXONOMY AND SOME ASPECTS OF THE ECOLOGY OF MARINE OSTRACODS IN THE PLANKTON OF INDIAN ARM, BRITISH COLUMBIA by ROBERT ALEXANDER McHARDY B.Sc., The University of B r i t i s h Columbia, 1958 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Zoology We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October, 1961 In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree tha t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s representatives. It i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Zoology  The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 3, Canada. Date October 6. 1961 I i ABSTRACT In I 9 6 0 a program was ca r r i e d put to„ study some aspects of the d i s t r i b u t i o n of planktonic ostracods i n Indian Arm, an i n l e t of the coast of B r i t i s h Columbia. As a r e s u l t , Paradoxostoma striungulum Smith. Phllomedes S P . « Conehoecia  eleeans Sars, and C. pseudohamata n.sp. were c o l l e c t e d , described and i l l u s t r a t e d . Of these species. C. eleeans and C, pseudohamata were abundant i n the plankton, and provided material f o r the diagnoses of growth stages and f o r the comparison of the adult stages with those c o l l e c t e d from other B r i t i s h Columbia i n l e t s and from the Ocean Weather S t a t i o n ttP" (50° N., 1^50 ( The d i s t r i b u t i o n s of Conehoecia elegans and C. pseudo~  hamata were studied i n r e l a t i o n to temperature, s a l i n i t y , oxygen, and l i g h t . The species were seldom found i n water above the thermocline and h a l o c l i n e . The general d i s t r i b u t i o n s of Conehoecia elegans and C. pseudohamata may have been p a r t l y influenced by the mixing between water long resident i n Indian Arm and water entering by way of the mouth of the I n l e t . . Both species generally inhabited waters having temperatures from 7 to 9 ° C , and s a l i n i t i e s from 26 to 2 7 ° / o o 8 Both occurred at depths greater than the shallow s i l l a t the mouthj the one l i v i n g more deeply seems to have been more r e s t r i c t e d to the i n l e t than the other. i i i D iurnal v e r t i c a l migration d i f f e r e d f or the two species except within the shallower part of the water column, where both seem to have descended i n the presence of l i g h t . The time of maximal breeding seems to have been i n the earl y summer for Conchoecia elegans and from early summer to early autumn for C. pseudohamata. Examination of stomach contents shows that both species were omnivorous. i v ACKNOWLEDGEMENT Many have contributed toward the completion of this t h e s i s . Dr. R. F. Scagel introduced the author to the th e o r e t i c a l aspects of b i o l o g i c a l oceanography and Dr. M. Gilmartin introduced him to the shipboard procedures employed. Mr. T. Killam contributed many exhaustive hours of technical assistance when_the s c i e n t i f i c crew was l i m i t e d . Several technicians, fellow students and the Masters and crews of the research vessels C.N.A.V. Whitethroat, C. N.A.V. Oshawa, and A. P. Knight also assisted i n c o l l e c t i n g data. The f a c i l i t i e s of the Insti t u t e of Oceanography, U.B.C, were made available by the di r e c t o r , Dr. G. L. Pickard. Miss D. Harlow assisted i n the processing of the b i o l o g i c a l data. Mr. M. Mirhej obtained c a l i b r a t i o n values f o r the Eppley pyrheliometer of the U .B.C. Climat o l o g i c a l Station, and Mr. D. Pierce, operating the st a t i o n , provided kind cooperation and h e l p f u l advice concerning c a l i b r a t i o n of a l i g h t meter. A number of people generously assisted with references and_In other ways. These include Dr. J . P. Harding, who kindly located specimens i n the B r i t i s h Museum (Nat. Hist.) and examined them fo r the author; Dr. F. Neave and Mr. R. J . LeBrasseur, who arranged for the author to examine specimens obtained from the Ocean Weather "P"; Miss M. Jurkela, Miss D. Harlow, and Mr. H. Wilke, who helped with the tr a n s l a t i o n V of f o r e i g n papers; Dr. P. A. Larkin and Mr. J . J . Magnuson, who gave advice on the s t a t i s t i c a l procedures regarding Ifche c a l i b r a t i o n of plankton samplers; Mr. T. Killam, who l a b e l l e d figures and inked graphs; and Mr. R. Buchanan and Mr. K. Roth, who introduced the author to techniques of photocopying. The Defence Research Board of Canada provided f i n a n c i a l assistance (DRB 9520-05) . Dr. B. M. Bary supervised most of the research and showed unceasing i n t e r e s t i n the author*s progress. Considerable improvement i n the manuscript resulted from his intensive c r i t i c i s m . v i TABLE OF CONTENTS Page TITLE PAGE i ABSTRACT . . . . i i ACKNOWLEDGEMENT . . . . . . . . . . . . . . i v LIST OF TABLES . v i LIST OF ILLUSTRATIONS . . . . x GENERAL INFORMATION 1 PART I. TAXONOMY Section I. INTRODUCTION h I I . METHODS 5 I I I . CLASSIFICATION 8 IV. SPECIES Paradoxostoma striungulum Smith Description. . . . . . . llt-Discuss ion 18 D i s t r i b u t i o n 19 Philomedes sp. .Description. • 20 Discussion 22 D i s t r i b u t i o n . . . 25 GENUS Conehoecia .Note regarding Endites of Maxilla 26 Conehoecia elegans Sars Description • 27 Discussion 38 D i s t r i b u t i o n 7^ Conehoecia pseudohamata n.sp. Description 7^ Discussion . 61 D i s t r i b u t i o n 65 V. GROWTH STAGES 66 VI. REGIONAL VARIATION i n Conehoecia elegans and Conehoecia pseudohamata. . . . 70 v i i TABLE OF CONTENTS (CONT'D) Page Part I I . ECOLOGY Section I. INTRODUCTION . 73 I I . METHODS 76 C o l l e c t i o n of Data Data Examined Treatment of Plankton Samples I I I . 'DISTRIBUTION OF OCEANOGRAPHIC FACTORS 82 IV. TIDE 87 V. LIGHT 89 VI. DISTRIBUTION OF CSTRACODS 89 V e r t i c a l D i s t r i b u t i o n Ceachoecia elegans Sars Conchoecia pseudohamata n.sp. Transverse and Longitudinal Distributions Transverse D i s t r i b u t i o n Conchoecia elegans Sars Conchoecia pseudohamata n.sp. Longitudinal D i s t r i b u t i o n Conchoecia elegans Sars Conchoecia pseudohamata n.sp. VII. SEASONAL VARIATION IN FECUNDITY 109 Conchoecia elegans Sars Conchoecia pseudohamata n.sp. VIII. FOODS of Conchoecia eLeean Sars and Conchoecia pseudohamata n.sp. • • I l l XX. DISCUSSION 112 SUMMARY 120 REFERENCES. . . . . . . . . . . . . . . . . . . . 12k TABLES 129 ILLUSTRATIONS . . . . . . . . . 132 v i i i TABLE OF CONTENTS (CONT'D) APPENDICES Page 1. CALIBRATION OF CLARKE-BUMPUS PLANKTON SAMPLERS IN THE FIELD 1 - 1 7 Introduction Apparatus Procedure Results Discussion Application to Plankton Summary i T a b l e 1 I I . THE SUBSAMPLER . . 1 - 3 Introduction Description Use Figure 1 . . , I I I . VARIABILITY DUE TO SUBSAMPLING, SAMPLING, AND POPULATION DIFFERENCES 1 - 7 Introduction Comparison of Variations V a l i d i t y of Subsampling Estimates Tables 1 to h ix LIST OF TABLES Table Page 1. Characteristics separating Conehoecia elegans Sars from Conehoecia discophora Muller (After Muller, 1906a) . . . . . ~. . . . . . . . 130 2, Growth factors of Conehoecia elegans Sars and C. pseudohamata n.sp. . . . . . . . . . . . . 131 X LIST OF ILLUSTRATIONS Figure Page 1. An ostracod (Plate I) . 133 2-7. Paradoxostoma striungulum Smith (Plates I & I I ) . . . 133-^  8-l"M-. Philomedes sp. (Plates I I & III) 13"H-5 15-35. Conchoecia elegans Sars (Plates I I I to V I I ) . . . . 135-9 36-55. Conchoecia pseudohamata n.sp. (Plates VIII to XI) . lhO-3 56-17. Growth stages (Plate XI) 1^ 3 58. Approximate s h e l l lengths f o r the growth stages of Conchoecia elegans Sars and C. pseudohamata n.sp. found i n Indian Arm. lhk 59. Frequency of s h e l l lengths among growth stages 1 (male & female), 2, and 3 of Conchoecia elegans Sars.l""+5 60. Approximate s h e l l lengths of specimens of Conchoecia elegans Sars c o l l e c t e d from various B r i t i s h Columbia i n l e t s . . . . lk6 61. Approximate s h e l l lengths of specimens of Conchoecia pseudohamata n.sp. c o l l e c t e d from S t a t i o n "P" and various B r i t i s h Columbia i n l e t s . • lh7 62. Indian Arm i n plan view and l o n g i t u d i n a l p r o f i l e (after Gilmartin, i960) ihQ 63. Longitudinal p r o f i l e * of the d i s t r i b u t i o n of temperature i n Indian Arm f o r selected months ofi960.1^ 9 6h. Longitudinal p r o f i l e s of the d i s t r i b u t i o n of s a l i n i t y i n Indian Arm for selected months of i960 150 65. The density of deep water at Station 6 during i960. 151 66. The v e r t i c a l d i s t r i b u t i o n of dissolved oxygen a t S t a t i o n 6 during i960 152 67. T i d a l curves and times at which stations were occupied i n i960 153 68. T i d a l curves, continued from F i g . 67 15""+ 69. Longitudinal p r o f i l e s of temperature and s a l i n i t y d i s t r i b u t i o n s occurring i n March, I960, during periods when r i s i n g tides of various heights occurred • • • • • • • • • • • 155 x i LIST OF ILLUSTRATIONS (CONT'D.) Figure Page 70. Depths of l i g h t penetration a t Stations 6 and 9 at times corresponding to those of daylight plankton c o l l e c t i o n s i n i960 156 71. Depths of quartiles f o r the v e r t i c a l d i s t r i b u t i o n of Conehoecia elegans Sars at Stations 6 and 9 i n I960 157 72. Depths of quartiles f o r the v e r t i c a l d i s t r i b u t i o n of Conehoecia pseudohamata n.sp. at Stations 6 and 9 i n I960. 7 158 73* V e r t i c a l d i s t r i b u t i o n of growth stages of Conehoecia  elegans Sars at St a t i o n 9> over a t*2i+-hourtB cycle i n July, I960 159 7^ . V e r t i c a l d i s t r i b u t i o n of growth stages of Conehoecia  pseudohamata n.sp. a t St a t i o n 9> over att2k hour" cycle i n July, i960 .,<>..,. 160 75« V e r t i c a l d i s t r i b u t i o n of Conehoecia pseudohama.ta n.sp., continued from F i g . 7^ . • • • • l6l 76. V e r t i c a l d i s t r i b u t i o n of Conehoecia pseudohamata n.sp., continued from F i g . 75. . • 162 77. The depth of l i g h t penetration against the depth of the f i r s t q u a r t i l e of the v e r t i c a l d i s t r i b u t i o n of Conehoecia elegans Sars at Stations 6 and 9 for selected months of i960 163 78. Distributions of Conehoecia elegans Sars on transverse ' p r o f i l e s across Indian Arm a t Stations 2, 6, and 12 during daylight i n July, i960 l6*f 79. D i s t r i b u t i o n of Conehoecia pseudohamata n.sp. on transverse p r o f i l e s across Indian Arm at Stations 2, 6, and 12 during daylight i n July, i960. . . . 165 80. Distr i b u t i o n s of Conehoecia elegans Sars a t night on lon g i t u d i n a l p r o f i l e s of Indian Arm during i960. • 166 81. D i s t r i b u t i o n of Conehoecia pseudohamata n.sp. a t night, on lon g i t u d i n a l p r o f i l e s of Indian Arm during i960 167 82. Concentrations of Conehoecia elegans Sars a t various stations along Indian Arm showing propor-tions of growth stages numbered (l(j# and ?•), 2, and higher than 2. Data from night c o l l e c t i o n s i n I960 l 6 8 x i i LIST OF ILLUSTRATIONS (CONT'D) Figure ~ Page 83. Concentrations of Conchoecia elegans Sars at various stations along Indian Arm showing proportions of growth stages numbered l(jiy and ?-), 2, and higher than 2. Data from daylight collections in I960 169 8h. Concentrations of Conchoecia pseudohamata n.sp. at various stations along Indian Arm showing proportions of growth stages numbered 1(# and $), 2, 3, and higher than 3« Data from night collections i n i960. . . . . . . . . . 170 85. Concentrations of Conchoecia pseudohamata n.sp. at various stations along Indian Arm showing proportions of growth stages numbered 1 {0/ and 2 ) , 2, 3, and higher than 3. Data from daylight collections in i960 171 86. Occurrences of Conchoecia elegans Sars at Stations 15 and 23 during I960 172 87. Occurrences of Conchoecia pseudohamata n.sp. at Stations 15 and 23 during I960. . 173 88. Average concentrations of Conchoecia elegans Sars and C. pseudohamata n.sp. in Indian Arm during selected months of i960 V?h 89. The proportion of adults to individuals in a l l stages and the proportion of females having most of their eggs mature, for Conchoecia elegans Sars in Indian Arm during i960 175 90. The proportion of adults to individuals in a l l stages and the proportion of females having most of their eggs mature, for Conchoecia  pseudohamata n.sp. in Indian Arm during i960 176 1 A STUDY QF THE TAXONOMY AND SOME ASPECTS OF THE ECOLOGY OF MARINE OSTRACODS IN THE PLANKTON OF INDIAN ARM, BRITISH COLUMBIA GENERAL INFORMATION The d i s t r i b u t i o n of zooplankton of the coast of B r i t i s h Columbia has been studied by Campbell ( 1 9 2 9 ) . LeBrasseur (195^)> Lea (1955)> Cameron (1957)> and Legare ( 1 9 5 7 ) • In these studies ostracods were seldom mentioned and then only as being present* The studies were exploratory and covered large areas* Except for Legare*s study, which included c o l l e c t i o n i n the f a l l , these studies were conducted during the warmer part of the year and, therefore , could provide l i t t l e information on seasonal changes* An account of seasonal changes has been given by Johnson ( 1931) £OT the plankton (excluding ostracods) of F r i d a y Harbor, Washington (U*S*A*), a l o c a l i t y adjacent to B r i t i s h Columbia. The present study was l i m i t e d to a s ing le taxonomic group and a r e l a t i v e l y l i m i t e d a r e a . This allowed considerable e f f o r t to be confined to the accurate d e s c r i p t i o n of r e l a t i v e l y few species and to the repeated sampling of various pos i t ions w i t h i n the a r e a . E s p e c i a l l y d e t a i l e d descr ipt ions are provided f o r those species occurring most abundantly i n the plankton s ince the 2 distributions of these are being related to environmental factors* Positive identification is required so that ecolo-gical findings may be associated with the species wherever they may be found* The recognition of possible v a r i a b i l i t y between intraspecific populations is regarded as being at least as important as the evaluation of deviations in the measurement of physico-chemical factors of the environment. Repeated sampling was necessary for the detection of diurnal and seasonal variation in horizontal and v e r t i c a l distributions* Sampling of the horizontal distribution was done at intervals of three to four kilometres and that of the ve r t i c a l distribution, at intervals of 3 0 m* between the top and bottom of the water column* For convenience, this investigation is reported in two parts. Information regarding the morphology and systematics of the species is presented i n Part I, Taxonomy. That per-taining to environmental relationships of these species is i n Part II, Ecology« P A R T I T A X O N O M Y If INTRODUCTION The plankton c o l l e c t e d from Indian Arm y ie lded four species of ostracods, two of them bel ieved to be prev ious ly unknown* Items presented and discussed below, and concerned with the taxonomy of these species ares f i r s t l y , diagnoses of major taxonomic categories ; secondly, descr ipt ions of adu l t specimensj t h i r d l y , d i s t i n g u i s h i n g features of growth stages for two of the species; and l a s t l y , comparison of d iagnost ic features and s h e l l measurements of adu l t specimens obtained from Indian Arm and other l o c a l i t i e s * 5 METHODS Much of the mater ia l to be used for d e s c r i p t i v e purposes was s ta ined , d i s sec ted , and mounted for microscopic examination* P o l y v i n y l lactophenol (Salmon, 19^9) was used extens ive ly as a medium f o r these procedures* S t a i n i n g of specimens was accomplished by adding methylene blue and l i g n i n pink to the medium* Specimens se lected for examination were placed i n i n d i v i d u a l depression s l i d e s f i l l e d with the s ta ined medium, and l e f t u n t i l coloured to a pre ferred in tens i ty* Adults of the l arger species were dissected and t h e i r parts arranged on microscope s l ides* Smaller specimens, too d e l i c a t e for d i s s e c t i o n , were transferred d i r e c t l y to s l i d e s * S t a i n i n g p r i o r to d i s s e c t i o n served to minimize the loss of parts during the i r transfer from the d i s s e c t i o n medium to the prepared s l i d e * S l i d e s were prepared using Turtox non-resinous mounting medium * as a r im to support the c o v e r s l i p , and p o l y v i n y l lactophenol as a mountant* For the drawing of s h e l l s , whole specimens were orientated and mounted i n g lycer ine j e l l y * Descr ip t ion -o f each sex of the two most p l e n t i f u l species was based on examination of from 2 to 15 specimens, the number depending on the amount of v a r i a t i o n detected i n p a r t i c u l a r organs* Whole specimens and parts of specimens were measured Item CMS - 10, General B i o l o g i c a l Supply House, Chicago, I l l i n o i s • 6 under the microscope using a finely divided eyepiece scale which had been calibrated against a micrometer scale of 200 divisions i n 2 millimetres* Occasionally, when comparing spines, I t was necessary to measure that component of length perpendicular to the stage of the microscope* This was accom-plished by comparing the number of divisions turned on the fine adjustment d i a l of the microscope with a calibration value derived by focusing between the upper and lower surfaces of a coverslip of known thickness* Shell measurements were taken from intact specimens, each orientated in a well of a transparent spot plate* Shell length was measured as the greatest distance along the shell below the rostrum on a line p a r a l l e l to the dorsal margin* Specimens with shells agape were not regarded as good material for measurement* Measurements are considered accurate within ± 2#* Often measurements of shell length were expressed statis-t i c a l l y (Freund, 1952; Snedecor, 1956; and Youden; 1952)* Although population parameters and indications of population differences may have been inferred from the stati s t i c s used, they were usually not intended for these purposes* Unless actually employed i n a s t a t i s t i c a l test, they were used merely as a means of expressing a sample of measurements in a concise manner* Only Figs* 8 and 5^ are free-hand drawings; most others were drawn using the Leitz "Prado1* microprojector* Where material required a high magnification or was mounted in 7 glycerine jelly, a camera lucida was used* Accompanying each figure is a reference scale which is a small section of a micrometer scale reproduced at the same magnification as used for the drawing* Homologies used in describing the limbs are those proposed by Skogsberg (1920)* He discussed in detail the pros and cons of adopting the various homologies suggested by previous workers, and has selected those he considers most likely to be true* 8 ? CLASSIFICATION CLASS CRUSTACEA ORDER OSTRACODA SUBORDER CYPRIFORMES FAMILY CYTHERIDAE SUBFAMILY PARADOXOST GMINAE GENUS Paradoxestoma Fischer Paradoxostoma striungulum Smith SUBORDER CYPRIDINIFORMES FAMILY CYPRXDINIDAE SUBFAMILY PHILOMEDININAE GENUS Philomedes Xilljeborg Philomedes sp. SUBORDER HALOCYPRIFORMES FAMILY HALOCYPRIDAE GENUS Conchoecia Dana Conchoecia elegans Sars Conchoecia pseudohamata n.sp. ORDER OSTRACODA* Characterized by having the entire head and body unsegmented and enclosed within a dorsally hinged bivalve shell (carapace)o Segmented appendages numbering not more than seven pairs, only two or three of them being thoracic (after Skogsberg, 1920$ Sars, 1928j and Kesling, 195D. Figure I is presented to show the general structure and orientation of the parts* 9 Skogsberg (1920) has defined five suborders* Three of these, namely, Cypriformes, Cypridiniformes, and Halocypri-formes, were represented i n the Indian Arm collections* SUBORDER CYPRIFORMES. Fresh-water and marine* Endopodite is the well developed branch of the second antenna* Sixth limb present with i t s vibratory plate more or less completely reduced, and with no endites* Seventh limb similar to sixth, vibratory plate always reduced, no endites* Copulatory organ c l e f t and produced near the brush-like organ* (After Skogsberg, 1920*) Four families* FAMILY CYTHERIDAE. Marine. F i r s t antenna with five to seven segments, i t s second and third segments fused. Second antenna with three or four segments, the last usually with three claws or bristles (the third often d i f f i c u l t to find) and with the exopodite a single, often un3egmented slender " s i l k -web" br i s t l e * F i f t h limb four-segmented with vibratory plate rudimentary or absent* Sixth and seventh limbs similar to f i f t h i n shape and siae. (After Muller, 189^ *) Two subfamilies. SUBFAMILY PARADOXOSTGMINAE. Second segment of f i r s t antenna without b r i s t l e s . Shell smooth or finely striated, strongly compressed. Mouth with l i p s . Masticatory process of mandible without teeth. (After Muller, 189*+.) About 15 genera* 10 GENUS Paradoxostoma Fischer. Lips form a con-tinuous ring on a strong prominent peristome (e.g. Fig.2, l i p s ) . Maxilla (e.g. Fig. 5) with the second and third masticatory-processes completely developed, but the f i r s t possessing only one or two bristles; with the palp either absent or represented by a single b r i s t l e . (After Muller, l89*t.) At least.26 Recent species. Paradoxestoma striuneulum Smith (1952). Terminal claw of second antenna broad for most of its length, but towards the tip, begins to curve and abruptly straightens to form a naked tip (Fig.3, cl.)« (After Smith, 1952.) SUBORDER CYPRIDINIFORMES. Benthic and planktonic marine. Exopodlte, the well developed branch of the second antenna. Sixth limb present and with endites. Seventh limb a peculiar worm-like cleaning organ. Copulatory organs paired, symmetrical, and more or less coalesced at the base. (After Skogsberg, 1920.) Four families. FAMILY CYPRIDINIDAE. Maxilla without a fringe of long closely apposed setae. Endopodite of maxilla with two or three segments; exppodite of maxilla unsegmented and with three b r i s t l e s . (After Skogsberg, 1920.) Two subfamilies. SUBFAMILY PHILOMEDININAE. In the male* Bristles of f i r s t antenna without suckers, two of the bristles very long and backwardly directed. Second antenna with second and 11 t h i r d segments of exopodite severa l times as long as vide* Mast icatory process of f i f t h limb (second maxi l la)without teeth* (After M u l l e r , 189*^ -, and Skogsberg, 1920*) Of the two recognized genera, males are unknown i n one, Pseudophilomedes (Mul ler , 1912, Skogsberg, 1920, and Korn icker , 1958*) GENUS Philomedes L l l l j e b o r g * Without an elongate tooth on the f i f t h limb of the female (After Kornicker , 1958.) Philomedes sp* Male specimen only . Endopo-d i t e of second antenna (Fig.12) with four basa l and two d i s t a l setae on the f i r s t segment and with a long h y a l i n e , non-annulated seta on the t h i r d segment* Seventh limb with four d i s t a l and three marginal setae (Fig*13)» Caudal furca with f i r s t , second, t h i r d , and f i f t h claws strong and the remaining s i x claws weak (Fig*! 1*)* (After author . ) SUBORDER HALOCYPRIFORMES• Wholly p e l a g i c , marine* Exopodite , the w e l l developed branch of the second antenna except i n the genus Thaumatocynris where both are developed. S i x t h limb present wi th w e l l developed v i b r a t o r y p late and no endites* Seventti limb very smal l wi th long setae . Copulatory organ s i n g l e , s i n e s t r a l . (After Skogsberg, 1920*) One family* FAMILY HALOCYPRIDAE* Four genera are w e l l establ ished* One of these, Conchoecia. has been s p l i t i n t o e ight genera by 12 Granata and Caporiacco (19^ 9) who have rev i sed the c l a s s i f i c a t i o n of Claus (1890)1. Of the rev i sed genera, however, the diagnosis of the one r e t a i n i n g the name Conchoecia f i t s both species from Indian Arm. Thus whichever c l a s s i f i c a t i o n i s chosen, the appropriate genus remains Conchoecia. Sy lves ter -Bradley and l i e s (1956)-*- proposed use of the plenary powers of the In ternat iona l Commission on Zoo-l o g i c a l Nomenclature to va l ida te the c u r r e n t l y accepted s p e l l i n g "Conchoecia1* for the o r i g i n a l generic name, "Conchaecla" Dana, i&%9 (Levinson, 1957). GENUS Conchoecia Dana. F i r s t antenna f i v e -segmented with the two terminal segments often fused and bearing f i v e setae (eg. F i g s . 19 & 20). Endopodlte of second antenna with a d i s t i n c t mammilla (processus mammillaris) on the anter ior margin of the f i r s t segment (eg. F i g s . 22 to 25)• (After M u l l e r , 1912.) About 100 spec ies . Conchoecia eleeans Sars (1865)1* A l s o described by Mul ler (1906a), Skogsberg (1920), Sars (1928), and by Claus (1891) who c a l l e d i t Paraconchoecia g r a c i l i s . S h e l l with two or three spines on postero-d o r s a l corner of r i g h t v a l v e , with l e f t asymmetric gland on pos tero-dorsa l corner of l e f t va lve , and with r i g h t asymmetric gland on postero~ventral corner of r i g h t v a l v e . F r o n t a l organ Not examined* x3 of female with capltulum and shaft joining at a level opposite the articulation of the second and third segments of f i r s t antenna (Fig*20)* Principal seta of male f i r s t antenna with a shield-shaped "oval organ" succeeded by a d i s t a l portion bearing two opposed rows of four br five spines each and tapering with-out appearing tubular or thin-walled (Figs, 19 & 21). Endopodite of male second antenna (Fig. 22) with terminal setae (£ & £) d i s t i n c t l y different in length and not enlarged at bases (After Muller, 1906a, and Skogsberg, 1920.) Conehoecia pseudohamata n.sp. Shell with shoulder vault raised so that dorsal and lateral surfaces of shell meet to form right-angled ridges which are prominent i n anterior half of shell, but become gradually reduced to obscurity i n posterior half (Figs. 36 to 39)* Shell with l e f t asymmetric gland on postero-dorsal corner of l e f t valve and right asymmetric gland on postero-ventral corner of right valve* Posterior margin of shell with at least seven groups of lateral glands, three or four per valve5 and, i n male, with dorso-medial glands (Figs* hO & J+l). Principal seta of male f i r s t antenna with two adjacent rows each of about 30 processes. Each process with a chitinous "T,s -shaped frame-work possessing, on i t s d i s t a l side only, a body of hyaline material (Figs* hh & »+5). Not examined* 1\ SPECIES Paradoxostoma striungulum Smith (Plates I & II, Figs.2 to 7) Description SHELL, The shell is delicate and translucent except for chitlnized articulations at the anterior and posterior extremities of its hinge line. The center of each valve possesses four antero-posteriorly elongate adductor muscle insertions arranged in a dorso~ventral row. Hairs are scattered sparingly over the surface of each valve, but are barely noticeable except along the free margins. The compound eye, as shown by an Immature female specimen mm. long (the only specimen whose shell was not noticeably distorted in preparation), lies somewhat inside the antero-dorsal curvature of the shell and is elongated along a line more or less parallel to this curvature. FIRST ANTENNA (Fig.3, ant. 1 ) . Of the six segments of the f i r s t antenna the f i r s t has neither hairs nor setae; the second may possess long fine hairs, but has no setae; and the third possesses an antero-distal seta about three-quarters to one times the length of the segment and may also possess long fine hairs. The fourth and the f i f t h segments possess two 15 a n t e r o - d i s t a l setae and one p o s t e r o - d i s t a l s e t a . The d i s t a l end of the s i x t h segment bears four s lender , c l o s e l y apposed, subequal setae, the longest of which approaches three times the length of the segment i t s e l f . SECOND ANTENNA ( F i g . 3 , a n t * 2 ) . The second antenna con-s i s t s of an unsegmented protopodi te , an endopodite of four segments and an exopodite of three or four segments* The pro-topodi te , which i s without ha irs or setae, i s joined d i s t a l l y to the endopodite to form the ambulatory par t of the limb* The f i r s t segment of the endopodite possesses a seta which i s p o s t e r o - d i s t a l l y located , s inuous, and about twice the length of the second segment* Pos ter o*d i s t a l l y s i tuated setae of the second segment are of unequal length , the longer being about twice the length of the shorter and near ly as long as the pos ter ior margin of the t h i r d segment* The t h i r d segment possesses a seta on the middle of i t s an ter ior surface as w e l l as one on i t s p o s t e r o - d i s t a l extremity* The four th segment has a short s l i g h t l y s inuous, p o s t e r o - d i s t a l seta and a longer, a n t e r o - d i s t a l seta which may be re ferred to as the "terminal claw". This terminal claw ( F i g , 3 , c l . ) i s broad throughout most of i t s l ength , then curves and abrupt ly s traightens to form a sharp p o i n t . On the l a t e r a l and medial surfaces of i t s broader p a r t , there are diagonal " s t r ia t i ons" which are often d i f f i c u l t to detectj these are continuous with shor t , heavy ha ir s occas iona l ly seen protruding on the outside of the curvature of the claw. 16 The exopodite i s segmented by two or three f a i n t hyal ine a r t i c u l a t i o n s * The d i s t a l a r t i c u l a t i o n may be i n v i s i b l e ; i f so , three Instead of four segments can be determined* MANDIBLE. The elongate protopodite of the mandible bears a long, s t y l i f o r m basal process from i t s d i s t a l end and a long , angular palp from i t s middle* The posture of the palp resembles a human fore l imb with upper arm downward, lower arm forward and long f ingers downward* One or two inconspicuous setae may occur on the d o r s a l (or sometimes a n t e r i o r ) surface of the "lower arm1* port ion* The d i s t a l p o r t i o n of the palp (see F i g * *+) possesses s i x long conspicuous setae and one short , s lender seta which may be d i f f i c u l t to see* Of the long setae, four are born on a d i s t a l p r o t r u s i o n ; one i s anter ior to th i s p r o t r u s i o n , and one, pos ter ior to i t * The short , s lender se ta , when v i s i b l e , i s anter ior to the other setae* MAXILLA* The max i l l a i s unsegmented* The v i b r a t o r y p l a t e , which i s s i tuated prox imal ly , has a long process extended ven-t r a l l y (Fig* 5, v i b . p r * ) . Of the setae of the v i b r a t o r y p l a t e , ten are d i rec ted d o r s a l l y ; approximately four (number d i f f i c u l t to d i s c e r n ) , p o s t e r i o r l y ; and two are d i rec ted towards the mouth from t h e i r or ig ins on the v e n t r a l l y extended process* These l a t t e r two setae are usua l ly of equal length and near ly twice as long as the process on which they are borne* In a d d i t i o n to the process of the v i b r a t o r y p l a t e , the max i l l a possesses three d i s t a l processes which may be designated, pos ter ior to a n t e r i o r , as f i r s t , second, and t h i r d , i n order of increasing length (see F i g , 5, pr* 1, pr* 2, pr, 3)« The f i r s t process possesses two setae, each about as long as the t h i r d process; the second bears f i v e setae, each about one-third longer than the process i t s e l f , and the t h i r d process has about f i v e setae, each about one-quarter longer than i t s parent process, FIFTH, SIXTH, & SEVENTH LIMBS (See F i g . 6), Each of these limbs has four segments terminated by a claw. On the f i r s t segment of the f i f t h , and usually on that of the s i x t h limb, a seta i s present oust proximal to the middle of the length of the anterior surface; on the seventh limb this seta i s absent or i s inconspicuously small. Just d i s t a l to the middle of the anterior surface of this f i r s t segment, a small seta i s present on the s i x t h and seventh limbs, but i s absent from the f i f t h limb. A l l three limbs possess an ant e r o - d i s t a l seta on the f i r s t and the second segments, no setae on the th i r d segment, and a terminal claw on the fourth segment. A l l segments may possess very short f i n e " h a i r s " on their anterior surfaces* On the t h i r d segment of the seventh limb, however, the anterior surface possesses a p a r t i c u l a r l y con-spicuous fri n g e of hairs on i t s d i s t a l h a l f ( F i g . 6, limb 7 ) . On the l a t e r a l surfaces of the f i r s t and second segments of the three limbs there appears an outline which suggests the presence of a d i s t a l l y directed seta (not shown In F i g , 6 ) . BRUSH-LIKE ORGAN. In the region of the f i f t h limbs, and only i n the male, there are two pairs of processes, one pa i r 18 directed dorsally and the other ventrally. Each process bears a terminal fan of long, soft, fine hairs. PENIS (see Fig. 7). The penis is located behind the seventh limbs and is closely united to the caudal furcae. I t has been found in several positions in the vertical plane, suggesting that i t may be moveable. Proximally the organ is roundedj d i s t a l l y i t is triangular and possesses two pairs of flap-like processes. Each member of the antero-ventral pair is chitinized, slender, and has a profile resembling a human footj those of the postero-dorsal pair, on the other hand, are transparent and broad. CAUDAL FUBCA (see Fig. 7). The caudal furcae are paired, and each furca is armed with two spines, one dorsal and the other ventral. The dorsal spine is stout and three to four times the length of the ventral one. The ventral spine may not be apparent in the mature female, probably because of i t s close apposition to the dorsal spine (ventral spine dist i n c t l y visible i n immature female). Discussion Smith's (1952) description of Paradoxostoma striungulum corresponds very well to four specimens (three adult males and one adult female) found i n the Indian Arm material. No adequate sh e l l measurements were obtained because the few 19 specimens available had been compressed during preparation of slides for microscopic examination. Lengths of the compressed shells were about 0*h8 mm* for the males and 0*59 mm* for the female, less than the 0*57 mm* and 0»6h mm* reported by Smith* Smith (1952) described and illustrated the shell, f i r s t antenna, second antenna, third walking leg (herein called the seventh limb) and the copulatory appendage (the penis). She stated that the flagellum (the exopodite) of the second anten-na was articulated In two places* A third, more d i s t a l articu-lation was indicated in the specimens from Indian Arm* In the female and i n two of the males this was barely perceptible but, i n the third male, i t was as distinct as those articulations found proximally (Fig* 3, ex*) This additional articulation and the occasional absence of a t r i v i a l amount of hair from segments of the f i r s t antenna seem to be the only items at variance with Smith's description* Probably these features represent variations within the species, Paradoxostoma strluneulum Smith. Distribution Specimens were taken in Indian Arm from depths of 0 m. at Station 9, 25 m. at Station 15, and 20 m. at Station 23 (see Fig. 62). Those described by Smith (1952) were captured at Departure Bay, Vancouver Island, B* C*, where they occurred 20 on the hydroid Obelia r near the surface of the water. The latter type of habitat may be normal for the species as the presence of claws terminating the limbs and the absence of natatory setae suggest that i t crawls and is not adapted for a plank tonic existence. Philomedes sp., male only (Plates II & III, Figs. 8 to ih) Description SHELL (see Fig. 8 ) . The shell is about 2 mm. long and more or less oval in shape. The anterior margin is complicated by a small rostrum and shallow rostral sinus j the posterior margin is partly straight, giving the shell a truncated appearance. The dorsal margin is less convex than the ventral margin. The surface of the shell is heavily pitted and bears sparsely scattered hairs, whereas the margin of the shell is comparatively smooth and possesses conspicuous hairs, especially anteriorly and posteriorly. FRONTAL ORGAN (see Fig. 9), The frontal organ is small and shaped somewhat like an arrow. FIRST ANTENNA (see Figs. 10 & 11). The f i r s t antenna has six segments: the f i r s t without setae, the second with three, the third with two or three, the fourth (Fig.11) with five and 21 the f i f t h with one. At the junction of the fourth and f i f t h segments i s a sensory seta ( F i g . 11, s.s.) with a swollen base covered with filaments, a tapered t i p which i s bifurcat e , and a length a t le a s t as great as that of the second segment. The s i x t h segment possesses three slender setae without filamentsj two short, stout setae with several filaments prot-ruding a t an angle from one side; and two extremely long, stout setae with s i m i l a r filaments inconspicuously appressed to the sid e . One of the l a t t e r two setae i s s l i g h t l y longer than the other and i s almost three times the combined length of the f i v e d i s t a l segments of the f i r s t antenna. SECOND ANTENNA. The protopodite and exopodite are the usual types f o r the genus. The three-segmented endopodite (see F i g . 12), on the other hand, shows a few c h a r a c t e r i s t i c s which are s p e c i f i c . The endopodite forms a clasping organ, the th i r d segment being flexed back onto the second. The f i r s t segment possesses four setae near i t s base and two others situated more d i s t a l l y . The second segment i s s t r a i g h t and, midway along the surface opposed to the th i r d segment, possesses two setae, the length of each between two- and three-tenths the length of the parent segment. The th i r d segment i s curved; at i t s base i s a seta which i s e n t i r e l y transparent and about three-quarters as long as the second segment; at i t s d i s t a l end i s a pair of spines which are minute, yet d i s t i n c t . SEVENTH LIMB (see Fig . 1 3 ) . The d i s t a l end of the seventh limb resembles a pair of gaping jaws with two spines on one side and six on the other (Fig . 1 3 ) . Adjacent to this structure are four d i s t a l setae arranged as two diametrically opposed pairs (Fig. 13 , d.s.). Situated proximally to these are three marginal setae arranged in a triradiate fashion (Fig . 1 3 , m.s.). CAUDAL FURCA (see Fig. l V ) . The furcae are paired and d i s t a l l y clawed. Each furca is armed with ten claws« The f i r s t , second, third, and f i f t h claws are distinctly curved and heavily chitinized; the fourth and the sixth to tenth claws are almost straight and nearly transparent. Discussion The description of this species is based on one mature male specimen. Appendages chosen for description were those which readily showed diagnostic features, or which provided comparison with the somewhat similar species, Philomedes  carcharodonta Smith, also found in B. C. waters. The shell, frontal organ, f i r s t antenna, and caudal furca of P. carcharodonta (&mith, 1952), agree closely with the specimen from Indian Arm. Smith's diagnosis, however, omits mention of the texture of the shell (which is heavily pitted in the Indian Arm form, Fig. 8) and differs from the Indian Arm specimen with regard to the setae of the "exopodite" (herein 23 called the endopodite) of the second antenna and of the seventh appendage (seventh limb)* In Philomedes carcharodonta (Smith, 1952) the f i r s t segment of the endopodite of the second antenna has five setae basally and one anteriorly* The second segment is said to have a long annulated seta on i t s d i s t a l margin* The origin of this seta would appear, however, to have been misinterpreted since, in the generic diagnosis, I t is placed at the proximal end of the third segment Skogsberg, 1920). In the Indian Arm specimen (Fig. 12), the f i r s t segment possesses four setae basally and two disto-anteriorly. A long seta at the proximal end of the third segment is not annulated, but entirely hyaline* Its placement on the third segment agrees with the generic diagnosis. The seventh limb of Philomedes carcharodonta has four d i s t a l setae and eight marginal ones (Smith, 1952). In the Indian Arm specimen (Fig. 13) this limb possesses four d i s t a l setae but only three marginal ones. So far as known, no other species of Philomedes has the same arrangement of strong and weak claws on the caudal furca that occurs in Philomedes carcharodonta and the Indian Arm specimen (see Fig. lk)* In some there is an antero-posterior graduation of claws from strong to weak} In others there is an intermingling of strong and weak* Often in the latter arrangement, a weak t h i r d claw i s placed with strong f i r s t , second, and fourth claws. The possession of strong f i r s t , second, t h i r d , and f i f t h claws with weak fourth and remaining claws, as found i n Philomedes carcharodonta and the Indian Arm specimen does not seem to have been equalled i n other species (Baird, 1850} Muller, 1891*-} Brady, 1907} Joday, 19P7J Lucas, 1931} Rome, 19^ 2} and Smith, 1952). For example, i s not known f o r the following: P. antarctica Bradv loneiseta Juday £• A p p e l l o f i Skoesbere MacAndrei (Baird) £• aspera Muller £. multichelata Kbrnicker P. a s s i m i l i s Brady P. o r b i c u l a r i s Brady P. Eueeniae Skoesbere P. paucichelata Kornicker P. elobosa (Lill.iebore) P. rotunda Skoesbere P. it l e v i s Muller P. t r i tuber culatus Lucas P. L i l l . i e b o r e i tears) P. lomae Juday The author Is not f a m i l i a r with the f u r c a l claws of Philomedes f l e x l l i s Brady, £ . F o l i n i Brady. P. sculpta Brady, and P. Wyville-Thompsoni Brady. These species, however, can be distinguished from the Indian Arm specimen by their heavy, sculptured s h e l l s (Skogsberg, 1920). Neither the Indian Arm form nor Philomedes carcharodonta can be confused with other species described from B r i t i s h Columbia (Lucas, 1931> and Smith, 1952). Nor, so f a r as known can either be mistaken f o r species from elsewhere (Baird, 1850 25 Muller, 189^ i Brady, 1907J Juday, 1907} Skogsberg, 1920; Rome, 19*f2; and Kornicker, 1958)* Although the specimen from Indian Arm d i f f e r s i n several features from the descriptions of Philomedes carcharodonta Smith (1952), i t could possibly be a variant of this species; on the other hand, i t could j u s t as wel l be new* To es t a b l i s h i t s Identity would require some knowledge of the consistency of the features describing i t * Unfortunately, with only the one specimen a v a i l a b l e , this consistency could not be estimated and, therefore, the i d e n t i t y of the specimen could not be shown* D i s t r i b u t i o n The specimen was taken a t night from a depth of 50 to 55 m« a t S t a t i o n 15 (bottom at about 60 m*, Fig. 62)* The f a c t that i t was caught at night; and only on one occasion, conforms with Skogsberg fs (1920) observations that the d i s t r i b u t i o n of cer t a i n species of the genus i s rather scattered and that most specimens are captured a t night* I t was co l l e c t e d i n A p r i l , but this may mean l i t t l e because specimens of other species have been caught i n the plankton a t a l l times of the year (Skogsberg, 1920* Perhaps, as i t s depth of capture suggests, the species inhabits water close to the bottom* 26 GENUS Conehoecia Note regarding Endites of Maxilla In this genus some confusion has a r i s e n over the number of masticatory endites on the maxilla* Juday (1906, p*17) counted three, but was probably i n error since the number for a l l halocyrids, including the genus Conehoecia. i s generally regarded as two (Skogsberg, 1920, pp* 557 - 8 and 608 - 9)* (Both Conehoecia elegans and £• pseudohamata possess two*) The o r i g i n a l d escription of the genus by Dana (1852) f a i l s to mention the endites of the maxilla* Possibly Juday (1906) interpreted the c l e f t end of the d i s t a l (cOxal) endite (Pigs* 28, c l * , and 52, c l * ) as two endites, or mistook the paragnath of the labium f o r an endite of the maxilla* The c l e f t end i s regarded by Skogsberg (1920, p* 558) as a weak b i f u r c a t i o n * Examination of Figs* 28 and 52 reveals the close association of paragnath and maxilla for the two species Conehoecia elegans and C» pseudohamata* In this close association, the paragnath could have been mistaken fo r an endite* The nearness of maxilla and paragnath can be preserved i n d i s s e c t i o n by removing the maxillae as a p a i r , and then cutt i n g them apart* Thus, the paragnath and maxilla remain connected by a piece of the body wall* Although d i f f e r i n g from an endite by i t s d e l i c a t e construction, the 27 paragnath may be regarded as resembling one i n size and p o s i t i o n . Conchoecia elegans Sars (Plates I I I to VII, F i g s . 15 to 35) Description SHELL (see F i g s . 15 to 18). The length of the s h e l l of the male varies between 1.5 and 1.7 mm. and i s about 1.1 times that of the female (see Table 2). I t i t s greatest depth the s h e l l i s s l i g h t l y less than one-half i t s length (Figs. 15 and 16). The postero-dorsal corner (Fig. 17) of the r i g h t valve possesses two or, occasionally, three spines. The locations of the two asymmetric glands are those usual f o r most species of the genus (Muller, 1912, F i g . 17, p. 59). The l e f t gland i s present beside the hinge-line (Fig, 17, 1. asm.) where i t opens by a pore near the postero-dorsal extremity of the l e f t valve. The r i g h t gland i s located at the postero-v e n t r a l extremity of the r i g h t valve where i t opens on the s h e l l edge. The l e f t asymmetric gland extends p a r t l y onto the r i g h t valve, but the majority of i t s glandular sacs are on the l e f t . Each gland consists of many large glandular sacs whose ducts discharge through a common pore, and may be c a l l e d a compound gland (Skogsberg, 1920). 28 In the male s h e l l , but not that of the female, each of the postero-dorsal extremities possesses a dense clu s t e r of pores (Fig# 17 > d-m.) resembling those of the dorso-medial group found i n some other species of the genus. These pores are often very d i f f i c u l t to detect. The medial glands are found i n both sexes; they discharge i n d i v i d u a l l y , or occasionally i n p a i r s , along most of the s h e l l margin. Pores on the anterior and v e n t r a l margins are somewhat recessed medially from the edge whereas those along the posterior margin ( F i g . 17, m.) are on the edge i t s e l f * The s h e l l i s composed of an outer and an inner layer between which granular material i s sandwiched. P a r a l l e l i n g the margin of the s h e l l are elongate structures which appear s u p e r f i c i a l l y as l i n e s (see F i g * 1 8 ) . The most medial l i n e seems to coincide with the dorsad l i m i t of that portion of the granular material which adheres to the inner layer (not apparent i n F i g . 18) and may be c a l l e d the inner margin. From the inner margin to the periphery of the s h e l l , further structures ares the l i s t , a projecting rim; the selvage, a projecting rim often making contact with the margin of the other valve; and the flange, forming the periphery (termin-ology from Sylvester-Bradley, 19*+1> and Kesling, 1 9 5 l ) » * n Conchoecia eleeans the inner margin and l i s t may be r e a d i l y observed around the margin except about the rostrum and r o s t r a l sinus. The selvage and flange appear to a l t e r i n relative prominence at different positions along the margin* The flange usually lies along the outer edge of the margin and generally is conspicuous* The selvage is inconspicuous on the anterior and posterior margins, but protrudes medially along the ventral edge (Fig* 18, s*v«). The rostral sinus has a simple, rounded edge, unadorned by any ridges* FRONTAL ORGAN (see Figs* 19 & 20)* The frontal organ is situated between the two f i r s t antennae and consists of a dis t a l capitulum and a proximal shaft* In the male (Fig*19) the shaft is in two subequal parts, the proximal part generally being slightly longer than the di s t a l part* The capitulum is approximately one-third the length of the shaft and forms no significant angle with i t so that the frontal organ, as a whole, is nearly straight* Minute hairs scattered on the ventral side of the capitulum are so fine that they can scarcely be detected. In the female (Fig. 20) the shaft is unsegmented, twice the length of, and slightly smaller in diameter than, the capitulum* A slight constriction marking the junction of capitulum and shaft occurs at a position nearly opposite the level at which the second and third segments of the f i r s t antenna join. FIRST ANTENNA (see Figs* 19 to 21). In the male (Fig,19), the large f i r s t and second segments are distinctly separated;, the third, fourth and f i f t h segments, on the other hand, are 3 0 Intimately articulated and d i f f i c u l t to distinguish* The second segment bears the retinaculum (Fig* 19, r.) on its dorsal surface* The f i r s t and third segments have no setae; the fourth segment possesses two setae, a. and b; and the f i f t h segment, three setae, c., d, and e. (terminology from Skogsberg, 1920). Seta a, is weak, transparent and usually directed backwards* If undamaged i t may be as long as the f i r s t antenna. Seta b is rather s t i f f , slightly chitinized, and approaches the combined length of the f i r s t two segments. Seta c. is transparent and approximately as long as the greatest depth of the second segment. Seta d is s t i f f , chitinized and similar in length to seta b» Seta e., often called the principal seta, is likewise s t i f f , chitinized, and similar in length to b. and d,« Approximately two-thirds along seta & is an oval or shield-shaped organ (Fig. 19, ov.) and d i s t a l to this are two diametrically opposed rows of four or five spines each (Fig. 21). Just proximal to the oval organ and just d i s t a l to the opposed spines, the seta may be reduced in diameter; d i s t a l to the second constriction, i t resumes i t s normal diameter and then gradually tapers to the ti p , without appearing tubular or thin-walled. In the female (Fig. 20) the joints between the five segments of the f i r s t antenna are indicated by being more thinly chitinized* The second segment may occasionally possess a small, fine seta on i t s dorsal surface* Four subequal sensory setae, representing setae a, b,, c,, and d, of the .. 31 male, form a terminal f a s c i c l e which approximates the combined length of the f i r s t two segments of the f i r s t antenna* Seta e, i s approximately twice the length of the sensory setae and, on i t s d i s t a l h a l f , bears widely spaced, slender hairs i n -c l i n e d toward the extremity. SECOND ANTENNA. The protopodite and exopodite of the second antenna are sim i l a r to those of other species of the genus. The endopodite (see Pigs. 22 to 25), on the other hand, shows a few s p e c i f i c c h a r a c t e r i s t i c s . In the male, the endopodite consists of three segments (Figs. 22 to 2k), The f i r s t segment i s the largest and has two mammillae on i t s antero-dorsal surface (Fig. 23). The proximal mammilla (processus mammillaris) bears a nipple-l i k e t i p and i s higher than wide; the d i s t a l one bears two spines, a, and b, and i s wider than highe Whether viewed l a t e r a l l y or medially, these two mammillae are seen to be simil a r i n area and hence, i n r e l a t i v e s i z e . On the second segment are two terminal b r i s t l e s , f and £ (Fig. 23)j sometimes a minute spine, e, at the base of seta £ (§. not i l l u s t r a t e d ) ; and two slender, antero-dorsally located spines, c, and d. Seta f., dorsal to i s str a i g h t , and nearly approaches the length of the combined protopodite and exopodite. Seta g i s approximately as long as the protopodite and i s shorter than £; i t bends l a t e r a l l y , crossing f at a po s i t i o n between four- and five-tenths of 32 the length of f. On neither right nor l e f t limbs, are the bases of these two setae swollen* The third segment (Figs* 23 & 2k) has a swollen base from which is produced a hook and three hyaline, scarcely tapering setae - h, i., and j,. The angle subtended by the proximal and d i s t a l portions of the hook approximates U-50. On the right antenna (Fig. 23) the proximal portion of the hook (between the swollen segment proper and the angle of the hook) is about one-tenth the length of the d i s t a l part. On the l e f t antenna (Fig.21+) the proximal portion of the hook forms a much smaller fraction of the length of the d i s t a l part. Overall, the l e f t hook is shorter, more slender and less chitinized than the right hook. In the female (Fig. 25) the endopodite consists of two segments with no indication of the third. The f i r s t segment is similar to that of the male. On the second segment, setae c and d may be either absent or represented by a single slender spine. Seta £ and & (on the second segment in the male.) and h, lt and j, (on the third segment in the male) are a l l terminal on the second segment in the female. Setae f and & are straight, closely apposed, and lateral to the sensory setae h, Xt a n d J,® Seta X Is placed medially to J, and is closely apposed to i t . Seta £ is longer than f and is approximately two-thirds the length of the protopodite. Seta jf and the sensory setae are subequal and approximately one-half the length of the protopodite. 33 LABRUM (see Frigs. 26 & 27). The labrum (upper l i p ) i s a prominant projection l y i n g anterior to the mouth; i t may be somewhat concealed by the second antenna and mandible (eg., F i g . 1, l abo ) . The anterior portion of the ventral surface i s concave (Fig. 26, cav.3. Just posterior to the middle of the length of this concavity are two chitinous thickenings (Figs. 26 & 27, c.th.) which appear to provide the points of o r i g i n f o r a pair of lo n g i t u d i n a l l y orientated muscles. On the postero-ventral extremity of the labrum there i s a hyaline plate (Fig. 27, p i . ) delimited l a t e r a l l y by a pair of combs and a n t e r i o r l y by insertions of the previously mentioned muscles. The posterior edge of this plate i s con-spicuously indented. LABIUM - Paragnath (see F i g . 28). The labium i s rep-resented by a pair of paiagna'ths (Fig. 28, prg.) attached to the body wall on either side of the mouth i n such a p o s i t i o n that they might be mistaken f o r an addit i o n a l pair of endites of the maxillae (see above under GENUS Conchoecia). MANDIBLE (see Fi g s . 30 & 3D. The mandible consists of one coxal, one basal and three endopodial segments (Fig. 30). The exopodite i s represented by a spined verruca appearing a n t e r i o r l y on the basale (Fig. 30, ex.). The coxale, measured along i t s anterior edge, i s somewhat longer i n the male than i n the female. The endite of the coxale (Fig.31) possesses three p a r a l l e l , toothed ridges and a masticatory 3 k pad. The ridges l i e , from outside to inside as well as from d i s t a l to proximal, as follows: the toothed ridge with 10 to 12 teeth, the d i s t a l t o o t h - l i s t with approximately 25 teeth, and the proximal t o o t h - l i s t with 15 to 20 teeth. The masticatory pad hears f i n e b r i s t l e s , coarse b r i s t l e s , and four conical hyaline teeth. In the male the basale, measured along the anterior edge, i s longer r e l a t i v e to the coxale and longer i n average measurement than i n the female. The width of the basale, measured across the endite, i s approximately the same i n males and females. Seven non-masticatory setae occur on the basale. Four of these occur on the enditej the f i f t h i s somewhat d i s t a l l y situated on the medial surface; and the s i x t h (the spine of the exopodial appendage) Is d i s t a l l y located on the anterior surface. The seventh seta i s a minute spine situated on the base of a small p a p i l l a (the epipodial appendage) located proximally on the inner side of the segment. The posterior edge of the endite i s p i l o s e near the toothed region ( p i l o s i t y not i l l u s t r a t e d ) . The masticatory part of the endite possesses two spines and s i x teeth i n a row, plus one tooth which i s l a t e r a l to the two or three most anterior teeth i n the row. No consistent difference i s observed between the length of the endopodite i n the male and the length of that i n the female. The f i r s t segment of the endopodite (Fig. 30, end.) has two posterior setae and one anterior seta. The second 35 segment has three setae situated d i s t a l l y on i t s anterior side and two midway on i t s posterior side. The thi r d segment possesses seven terminal setae and i s pi l o s e on the d i s t a l t h i r d of i t s anterior surface. The surfaces of the second and t h i r d endopodial segments, herein c a l l e d anterior, are ac t u a l l y more or less v e ntral when the limb i s flexed i n i t s usual manner (Fig. 30). MAXILLA (see F i g s . 28 & 29) . The maxilla consists of f i v e segments, namely, the procoxal, coxal, basal, and f i r s t and second endopodial segments (Fig. 28) . The procoxale has an endite which bears nine terminal b r i s t l e s of which the two most dorsal have long hairs (not shown i n F i g . 28) and the others are bare or have short h a i r s . The endite of the coxale i s c l e f t terminally (Fig. 28, cL). Spines on the endite are arranged i n three groupss two spines are mid-dorsalj s i x or seven are terminal and dorsal to the cleft} and f i v e are terminal and ventral to the c l e f t . The basale (Fig.2 8 , bas.) has a single spine on an an t e r o - l a t e r a l verruca. The f i r s t segment of the endopodite bears s i x setae along i t s anterior surface, a group of three on i t s posterior sur-face, and a few small transparent spines on Its d i s t a l end ( l a t t e r not shown i n F i g , 28) . The second segment (Fig. 29) ends In f i v e spines and may be pi l o s e a n t e r i o r l y , FIFTH LIMB (see F i g . 32) . The f i f t h limb consists of the protopodite, endopodite, and f i r s t , second, and t h i r d 36 exopodial segments, Distally on the anterior edge of the protopodite is a two-bristled proximal endite and a three-bristled d i s t a l endite (Fig,32, p. edt. & d.edt.). Proximally and postero-laterally on the protopodite is a three-lobed vibratory plate. The dorsal lobe has four or five setae, the middle lobe five, and the ventral lobe four setae, A small seta, usually the most dorsad on the dorsal lobe, occasionally may be absent. The other setae are long and possess slender, pinnately arranged hairs (hairs not shown in Fig. 32). The endopodite is the knee-like portion of the f i f t h limb (Fig, 32, end.) and is not distinctly marked off from the protopodite. Terminally the endopodite possess four claw-like spines (only two of which are heavily chitinized) and four slender, almost straight bristles. The exopodite is distinctly marked off from the rest of the limb (Fig. 32, ex.). Of the setae of the f i r s t segment, two are ventral and medial, four proximo-ventral, and three disto-ventral; one is disto-dorsal and one mid-lateral. Some pil o s i t y is found on the medial side of the segment. The second segment has one mid-dorsal bristle and two mid-ventral bristles, A male specimen from Saanich Inlet was found to have three aid-ventral bristles on the right limb, but the usual two on the l e f t . The three bristles of the third segment are terminal and unequal in length. 37 SIXTH LIMB (Figs. 33 & 3*0. The sixth limb consists of the protopodite, endopodite and f i r s t , second, and third exopodial segments. The protopodite is without,endites but has a vibratory plate of three lobes (Figs. 33 & 31+> v i b e ) . The dorsal lobe has five to seven setae, the middle lobe has f i v e , and the ventral lobe also has f i v e . A small seta, usually the most dorsal on the upper lobe, may be absent. The other setae are long and possess slender, pinnately arranged hairs (hairs not illustrated). The endopodite is indicated by two widely separated setae (Figs. 33 & 3^ > end.). The exopodites of the two sexes are similar in the relative proportions of their four segments but different in their overall lengths. The exopodite of the male sixth limb (Fig. 33, ex.) is considerably longer than that of the female and bears three terminal setae which are subequal in length and longer than the ventral edge of the limb. The exopodite of the female sixth limb (Fig. 3^, ex.), on the other hand, carries three terminal setae which are unequal i n length, the longest being only about sixth-tenths the length of the ventral edge of the limb. SEVENTH LIMB. The seventh limb consists of two fused seg-ments bearing terminally a long dorsal seta and a relatively short ventral seta. PENIS (see Fig. 35). The penis is sli g h t l y "S" shaped with i t s tip directed posteriorly. Two chitinized ducts, one 38 from the region of the testes and one from the proximal part of the penis, anastomose halfway down the length of the penis and continue d i s t a l l y as a single duct. A f t e r following a course around the t i p of the penis, this duct opens somewhat a n t e r i o r l y . Just above this opening, on the l e f t side of the penis i s the copulatory appendage, a small antero-ventrally projecting f l a p (Fig. 35, ap.). Four to s i x , or possibly seven, oblique muscle bands are located between the proximal t h i r d and d i s t a l quarter of the penis• CAUDAL FURCA (see F i g . 35)- The caudal furcae, a t the d i s t a l end of the abdomen, are each armed with a single annulated claw followed by seven non-annulated claws. Cn the posterior edge of each claw i s a double row of short s p l n e l e t s . There i s no unpaired b r i s t l e situated posterior to the claws. The depression between the furcae i s p i l o s e . Discussion Probably the only species which can be confused with Conchoecia elegans is C. discophora. These species are s i m i l a r i n most respects including the c h a r a c t e r i s t i c "S™ shaped penis and the peculiar "oval organ" adorning the p r i n c i p a l seta (seta e) of the f i r s t antenna of the male. 39 Other species have some other type of equipment taking the place occupied by the oval organ. For some species the equipment of the p r i n c i p a l seta of the male does not appear to be described. In some cases species were established on the descriptions of females or immature forms, but were l a t e r shown to be synonymous with species f o r which the males (and the equipment of their p r i n c i p a l setae) were described. Juday (1907) acknowledged that Conchoecia r i t t e r i Juday (1906) f o r which only the female had been described, was a synonym f or C± ametra Muller (1906a) f o r which the male had been described. Skogsberg (19^6) claimed that Cj, zetesios Fowler (1909) i s an immature form of C. macrocheira Muller (1906a), and that the male of C. hamata Vavra (1906) Is the same as the male of C. macrocheira. The equipments of the p r i n c i p a l setae of the males of C. ametra and C. macrocheira are not oval organs. Diagnoses of Conchoecia b r e v i r o s t r i s and C^ i n f l a t a by Dana (l8|+9) are generalized and do not mention the equipments of the p r i n c i p a l seta of the male f i r s t antenna; they f a i l i n other respects to d i s t i n g u i s h between these and many of the recently described species. Even so, one would expect to f i n d a des c r i p t i o n of this equipment i f i t s structure were as obvious as i n C. elegans. Since Dana did mention this equipment i n the diagnosis of another s.pecies, C. a g i l i s . but not of C. b r e v i r o s t r i s and C. i n f l a t a , one may assume the p o s s i b i l i t y that equipments of the l a t t e r two species were i n s u f f i c i e n t l y ho d i s t i n c t i v e to be of diagnostic value. ii Muller (1906a) includes the two species, Conehoecia  elegans and C. discophora. i n his elegans-group» He j u s t i f i e s this grouping on the basis of a f f i n i t i e s between the two species within the group and differences between these species and those i n other groups. The following paragraph on the elegans-group has been translated from Muller (1906a, p. 67). "Elegans-group" " S h e l l small, d e l i c a t e , the r i g h t postero-dorsal corner i s produced i n t o a usually d i s t i n c t point, whereas the l e f t i s not. Compound glands as usual (p.3^)* P r i n c i p a l seta of the f i r s t antenna of the male with a short double row of long, de l i c a t e b r i s t l e s , which are stuck together i n such a way that both rows almost form an oval l e a f . I t [the imale]is:sbarply characterized by this peculiar structure. For the female, I am unable to give any p o s i t i v e c h a r a c t e r i s t i c . They [females] belong to the small d e l i c a t e species, measuring at the most 2.1 mm., usually considerably l e s s , d i f f e r i n g from the forms of s i m i l a r s i z e i n the spinifera-group by the absence of p i l o s i t y on the p r i n c i p a l seta of the f i r s t antenna; from those [females] of the procera-group (to which they are very s i m i l a r ) by the somewhat stronger development of the f i r s t antenna (always over one h a l f the f r o n t a l organ), sometimes also by the presence of the dorsal b r i s t l e of the f i r s t antenna; and from those [females] of the dentata-group by the absence of a clear s h e l l sculpture." In order to di s t i n g u i s h Conehoecia elegans from C. dlsco- phora, Muller (1906a) suggested c a r e f u l comparison of the struc-tures of the endopodite of the second antenna i n the males and comparison of the s h e l l and f r o n t a l organ i n the females, n Muller describes the s h e l l of C. elegans as being less trans-parent, less elongate and, on the posterior margin, more curved. To Identify specimens by use of this d e s c r i p t i o n alone would require close comparison with a wide range of i d e n t i f i e d mater-i a l . Comparison of male endopodites and female f r o n t a l organs, on the other hand, seems to he a more productive means of i d e n t i f y i n g specimens. In Table 1 the Indian Arm material i s compared with descriptions of C. elegans and C. discophora with regard to the p r i n c i p a l seta of the male f i r s t antenna, the endopodite of the male second antenna, and the r e l a t i v e lengths of f r o n t a l organ and f i r s t antenna i n the female. In these three features the Indian Arm material i s i d e n t i c a l to C,. elegans. The p r i n c i p a l seta of the male f i r s t antenna does not possess a tubular, thin-walled d i s t a l portion; the terminal setae (f and j*) of the endopodite of the male second antenna are d i s t i n c t l y d i f f e r e n t i n length and do not possess swollen bases; and i n the female the f i r s t antenna extends farther a n t e r i o r l y than does the junction of the capitulum and shaft of the adjacent f r o n t a l organ. Thus the Indian Arm material i s i d e n t i f i e d as C. elegans Sars. Skogsberg (1920) has described i n d e t a i l the s h e l l , f r o n t a l organ, f i r s t and second antennae, mandible, labrum, maxilla, f i f t h and s i x t h limbs, penis and furca of the male, and the s h e l l , f r o n t a l organ, f i r s t and second antennae, and s i x t h limb of the female. He examined specimens from the S c a n — dinavian waters of Skagerrak, Kattegat, and Lofoten and from the A r c t i c , A t l a n t i c and Antarctic Oceans. He found that females from both the A r c t i c and Antarctic were on an average somewhat smaller than the males. This r e l a t i o n s h i p was also true for male and female specimens collected from Indian Arm and other Bri t i s h Columbia inlets (Fig. 60). A Student-t test was performed, as outlined by Youden (1951)> to test for difference between the mean lengths of kk male and k5 female shells. The " t t t calculated was 3*7&t greater than the 2„6k expected to occur by chance only once in a hundred timeso Thus the sexes have been shown to differ significantly with respect to their shell lengths. Shell lengths given by Skogsberg (1920) for specimens from the interpolar waters of the Atlantic and Antarctic (about 1.2 to 2.0 mm. for males) seem to be less than those (1.8 to 2.3 mm. for males) from the more northern waters of Skagerrak, Kattegat, Lofoten and the Arctic Ocean, and the more southerly waters of the Antarctic, but are similar to those from the inlets of Bri t i s h Columbia (about l.*f to 1.7 mm0 for males, see F i g . 60). A process found on the postero-dorsal corner of the right valve of male specimens from the Scandinavian waters (Skogsberg, 1920, Fig. 3) was not present i n the Antarctic specimens. This process was absent from the specimens of Bri t i s h Columbia waters. Skogsberg*s (1920) description of the general form, surface sculpture, selvage, and glands of the shell are not at variance with the material described here. However, the ratio of length to height of the male shell differs from the material of Skogsberg. The material from Indian Arm and the *3 other inlets has shown a ratio of 2.2} Muller (1906a) gives i t as less than that for Conchoecia dlscophora, i.e., less than tt 2.5} Skogsberg gives the ratio as 2©6. Muller's information apparently shows no disagreement with the ratio for Indian Arm material, whereas Skogsberg's seems to d i f f e r . Possibly the discrepancy between Skogsberg's ratio and that of the local material is part of the variation to be expected when specimens from widely separated localities are being compared. As far as known, evidence of dorse-medial glands i n Conchoecia elegans has not been previously detected} they were not described by Muller (1906a) or Skogsberg (1920). In the present material, however, pores of these glands were found i n the males. Their detection was so d i f f i c u l t that they were overlooked in at least 20 males from Indian Arm and the other i n l e t s . When the pores were f i n a l l y observed and recognized as resembling those of the dorse-medial groups of glands found i n other species of Conchoecia. preparations previously made were re-examined. As a result, a l l of the male specimens were found to possess the pores of dorso-medial gland-groups on their shells. I t would seem that the pores of dorse-medial groups of glands probably were present, but overlooked, i n the material examined by previous inves-tigators. Taken separately, Skogsberg's (1920) descriptions of the male frontal organ and the male f i r s t antenna suit the Indian Arm material very w e l l . I f the two organs are compared with respect to the length of the capitulum and the greatest depth of the second segment of the f i r s t antenna, however, a d i f -ference i n proportion may be found. In the present material, from Indian Arm and the other i n l e t s , the r a t i o i s l.V, with the capitulum being r e l a t i v e l y larger; i n Skogs berg's material the r a t i o was about 1. I t i s u n l i k e l y that an error such as misorientation of the antenna would have caused such a d i f -ference i n the r a t i o s . This v a r i a t i o n , although s l i g h t , i s probably r e a l , and perhaps i s to be explained i n a si m i l a r way to the differences i n the length-height r a t i o s of the s h e l l . t i . Muller (1906a) describes the f i r s t antenna but does not mention the two groups of spines d i s t a l to the oval organ. Perhaps this omission was due to his using i l l u s t r a t i o n s (Muller, 1906a., PI. XIII, F i g s . 8 & 12) of the p r i n c i p a l seta and oval organ of the male of Gonchoecia dlscophora ( i n which the spines are not shown) as a substitute f o r the same i n C. elegans and, as a r e s u l t , omitting mention of these spines i n his diagnosis. The spines i n the Indian Arm material are simi-l a r to those described and i l l u s t r a t e d by Skogsberg (1920) for G. elegans. Except f o r f a i l i n g to mention the presence of a dorsal seta on the second segment of the f i r s t antenna, the descriptions of the female f r o n t a l organ and f i r s t antenna by Skogsberg (1920) f i t those of the Indian Arm material. According to Muller (1906a, p. 69)",,.die dorsale Borste am 2. Glied scheint. s tets zu f e h l e n . " , i . e . , the d o r s a l b r i s t l e on the second seg-ment always seems to be absent. The wording suggests that Mul l er was not convinced of the t o t a l absence of th is s e t a . Furthermore he used the presence of th is seta as a poss ib le means of d i s t i n g u i s h i n g females of the elegans-group from t those of another group (Mul ler , 1906a) and mentioned that , i n C . d lsconhora. the d o r s a l seta i s " . . . l e i c h zu ubersehen", i . e . , easy to overlook (Mul ler , 1906a, p.68). In females from the Indian Arm m a t e r i a l , the d o r s a l seta i s present on one or both of the f i r s t antennae about as often as no t . Skogsberg (1920) describes the features and r e l a t i v e s izes of segments and setae of the male and female second antennae. These descr ipt ions f i t the Indian Arm m a t e r i a l i n a l l r e s p e c t s . The fo l lowing case of v a r i a b i l i t y , however, was not mentioned by Skogsberg* The r e l a t i v e lengths of the exopodite and i t s longest seta range from 5*0 s 10 to 8.0 x 10 but average 5*6 s 10, i . e . , the same as the h t 7 estimated by Skogsberg. Skogsberg (1920) described the mandible of only the male of Conchoecia eleeans and d i d not mention that i t d i f f e r e d from that of the female. In the Indian Arm m a t e r i a l , the coxale and basale of th i s limb were found to be r e l a t i v e l y longer i n the male (see above d e s c r i p t i o n ) . Skogsberg*s (1920) descr ipt ions of the s e ta t ion and p i l o s i t y of the max i l l a and the f i f t h and s i x t h limbs of the male and the s i x t h limb of the female f i t the Indian Arm *f6 m a t e r i a l w e l l . Skogsberg counts four to s i x oblique transverse muscles i n the penis* The same was found f o r the Indian Arm m a t e r i a l a l though, i n one specimen, a seventh band of muscle might have been interpreted as being present* Skogsberg mentions that no unpaired b r i s t l e i s present on the caudal furca of the male* This i s a l s o true for both males and females of the Indian Arm mater ia l* In s e v e r a l respects the present mater ia l appears to d i f f e r from previous descr ipt ions* Features such ass pores of dorse-medial glands i n the male s h e l l , spines d i s t a l to the ova l organ of the male f i r s t antenna, d o r s a l setae on the female f i r s t antennae, and sexual dimorphism of the coxale and basale of the mandible, appear to have been omitted from, previous descr ipt ions* On the other hand, di f ferences i n the proport ions of the length to height of the s h e l l , and of length of the capitulum to depth of the second segment of the f i r s t antenna i n the male, p o s s i b l y can be a t t r i b u t e d to the n a t u r a l v a r i a t i o n expected between specimens gathered a t widely separated locat ions* Compared to the s i m i l a r i t i e s between Indian Arm mater ia l and previous d e s c r i p t i o n s , these di f ferences may be regarded as r e l a t i v e l y t r i v i a l both i n number and i n d iagnost ic value* Thus there would appear to be l i t t l e doubt that the Indian Arm m a t e r i a l i s Conchoecia  elegans Sars • D i s t r i b u t i o n Conehoecia elegans was regarded by E l o f s o n (19^1) as a probably cosmopolitan spec ie s . I t has been reported to occur i n the A t l a n t i c Ocean from 79° 58• N . to 55° $. (Skogsberg, 1920), i n the Indian Ocean from 13° 2* N . to 27° 59* S . (Mul ler , 1906a), and i n the western P a c i f i c Ocean a t 0° 17* S . , 129° lk* E . and h° 30' S . , 1 2 8 ° 20* E . (Mul ler , 1906b, p . 37). L o c a l l y , i n the eastern P a c i f i c , the species has been taken from the reg ion of Vancouver I s l a n d , B r i t i s h Columbia (Smith, 1952). During the present study, l t was c o l l e c t e d between M$° 37* and 50° 53* N . from various i n l e t s of Vancouver Is land and the mainland of B r i t i s h Columbia (see F i g . 60, under Region) . Conehoecia pseudohamata n . sp , (Plates VIII to X I , F i g s . 36 to 55) Descr ip t ion SHELL (see F i g s . 36 to hi). The length of the female s h e l l averages about times that of the male (from two means of 16 measurements each) , and has been found to range from 2 to 3 mm. (see F i g . 6 l ) . The depth of the male s h e l l »+8 i s about 0*56 of i t s length and that of the female about 0 * 5 9 (a lso from 16 male and 16 female specimens* In both sexes there i s a depression about midway along the d o r s a l surface of the s h e l l * In the female the depth i s greater pos ter ior to th is depression whereas i n the male i t i s near ly the same a n t e r i o r l y and p o s t e r i o r l y (Figs* 36 & 3 7 ) « The an ter ior h a l f of the d o r s a l surface of the s h e l l forms a shoulder v a u l t over the heav i ly muscled f i r s t segments of the second antennae (Figs* 38 & 3 9 ) * Dorsa l l y the shoulder v a u l t i s f l a t , a n t e r i o r l y l t becomes the rostrum, and on e i t h e r s ide l t meets the l a t e r a l surface a t r i g h t angles to form a r idge* Pos ter ior to the bases of the second antennae, each r idge converges media l ly and blends i n t o the dorso-l a t e r a l sur face , and the d o r s a l surface becomes c l o s e l y con-toured to the body* The pos tero-dorsa l extremit ies of both valves may be e i t h e r rounded or b l u n t l y pointed* Although the l e f t extremity may,be s l i g h t l y more prominent, i t i s s i m i l a r i n shape to that on the r i g h t * In general the features of the s h e l l margin — inner mar-g i n , l i s t , se lvage, and f lange — bear the usual r e la t ionsh ips to one another (see d e s c r i p t i o n of Conehoecia elegans. s i x t h paragraph)* The selvage becomes progress ive ly more prominent from mid-ventra l l y to a n t e r i o r l y * This prominence i s es-p e c i a l l y not iceable from a v e n t r a l view (Fig* 39» s*v*)* *9 The locat ions of the two asymmetric glands ( F i g s . ho & hi, l . a s m . & r .asm. ) are those usual f or most species of the genus (Mul ler , 1912, F i g . 17, p«59). The l e f t gland i s present beside the h inge - l ine where l t opens by a pore near the pos tero-dorsa l corner of the l e f t va lve ; the r i g h t gland i s located a t the poster o -ventra l corner of the r i g h t valve where i t opens on the s h e l l edge. The l e f t asymmetric gland extends p a r t l y onto the r i g h t va lve , but the major i ty of i t s glandular sacs are on the l e f t . Each gland consis ts of many large glandular sacs whose ducts discharge through a common pore , and may be c a l l e d a compound gland (Skogsberg, 1920). These glands are s i m i l a r i n both sexes; the d i f f e r -ences between the l e f t asymmetric glands apparent i n F i g s . 0^ and *+l, are probably due to varying p h y s i o l o g i c a l states of the p a r t i c u l a r specimens chosen f o r i l l u s t r a t i o n . In the male, the pos tero-dorsa l extremity of each valve possesses a dense c l u s t e r of medial glands, the dorso-medial group ( F i g . M), d -m. ) . These c lus ters are absent i n the female. In both sexes there are other medial glands of a less conspicuous nature which occur s i n g l y o r , less commonly, i n p a i r s along the margin of the s h e l l wherever the selvage i s found (F igs . kO & hi, med.) . Where the selvage i s elevated on the antero -ventra l p a r t of the s h e l l margin the pores of these glands are less r e a d i l y seen, but where l t i s f l a t t ened each i s found opening on a minute c o n i c a l e l e v a t i o n . 5 0 Occas ional ly there i s a s l i g h t concentrat ion of these medial glands i n a reg ion jus t d o r s a l to the r i g h t asymmetric g land. These, however, do not form a conspicuous c l u s t e r l i k e those of the dorso-medial group of the male* The medial glands are d i s t ingu i shab le from other glands which are present on the pos ter ior margin i n that the i r pores are d i s t i n c t l y recessed from the edge* Seven or e ight groups of l a t e r a l glands occur on the p o s t e r i o r margin (Figs* ho & hi, l a t* )* E i t h e r three or four of these are present on each valve* One i s s i tuated w i t h i n the d o r s a l three-tenths of the pos ter ior margin* and the remaining two or three are located w i t h i n the v e n t r a l four-tenths* The number of v e n t r a l groups, with almost equal frequency, are (1) two on the r i g h t valve and three on the l e f t , (2) three on the r i g h t and two on the l e f t , or (3) three on each valve* Usua l ly there i s only a s ing le group d o r s a l l y , but occas iona l ly there may be two, one or both of which may be small* Although t h e i r glandular port ions may be i n d i s t i n c t , the pos i t ions of these glands may be determined by recogn i t i on of the tube-l i k e terminal port ions of the i r ducts which l i e s ide by s i d e , opening very c lose to the edge of the s h e l l * FRONTAL ORGAN (see F igs* h2 and ^ 3 ) » The f r o n t a l organ or ig inates somewhat a n t e r i o r l y to the bases of the two f i r s t antennae and l i e s along the mid - l ine between them* B a s i c a l l y i t has two p a r t s , a d i s t a l capitulum and a proximal shaft* In the male ( F i g . h2) the shaft i s segmented a t a l e v e l with the junct ion of the f i r s t and second segments of the f i r s t antenna. Usua l ly i n the genus there are only two segments (Skogsberg, 1920, p . 613), but i n th is species there i s often fur ther segmentation c u t t i n g of f the basa l t h i r d of the t y p i c a l proximal p a r t (Fig* *+2, p . s f t . 1). The d i s t a l segment of the shaf t i s about one and a h a l f times the length of the t y p i c a l proximal p a r t (often two-segmented) and s l i g h t l y longer than the capitulum. I t jo ins the capitulum i n the v i c i n i t y of the t h i r d segment of the f i r s t antenna. The capitulum i s v e n t r a l l y I n c l i n e d , d o r s o - v e n t r a l l y f l a t t ened and roughly uniform i n depth; l t tapers i n width from a broad base to a more or less b l u n t l y pointed t i p . Shor t , d i s t a l l y d i rec ted h a i r s occur on the proximal h a l f of i t s d o r s a l surface , on the proximal two-thirds of i t s l a t e r a l surfaces , and on the proximal three-quarters of i t s v e n t r a l sur face . In a d d i t i o n , a few ha ir s may occur towards the t i p along the mid- l ine of the v e n t r a l sur face . In the female the f r o n t a l organ ( F i g . ^3) i s r e l a t i v e l y s t r a i g h t . I ts shaft i s undivided and joins the capitulum j u s t beyond the t i p of the f i r s t antenna. The capitulum i s about two-thirds the length of the shaft and, except a t i t s s l i g h t l y sinuous and acute ly pointed t i p , i s more or less uniform i n depth. Unl ike the capitulum i n the male, that i n the female appears to be l a t e r a l l y compressed. Hairs on the capitulum of female f r o n t a l organ have a s i m i l a r d i s -t r i b u t i o n to those of the male, but are considerably coarser , being almost s p i n e - l i k e . FIRST ANTENNA Csee F i g s . **2 to **5)« The f i r s t antenna cons is t s of f i v e segments, the f i r s t two being d i s t inc t ly -segmented, subequal i n l ength , and by f a r the longest . The t h i r d , f o u r t h , and f i f t h segments are int imate ly a r t i c u l a t e d so that they are d i f f i c u l t to d i f f e r e n t i a t e . In the male ( F i g . k2) the second segment bears the ret inaculum, a c law- l ike dorse-medial ly s i tuated s tructure having a swollen base. The f i r s t and t h i r d segments are without setae; the four th possesses setae a. and t>; and the f i f t h bears setae c, d , and e, (terms from Skogsberg, 1920). Seta a, ( F i g . k2) i s bent sharply forward, then downward, and curved backward and upward so that i t resembles a s i c k l e . The perpendicular distance from the base of this contorted seta approximates the length of seta c,. Both setae a and c, are h y a l i n e , s carce ly tapered, and rounded a t the i r t i p s ; they are c a l l e d sensory setae (Skogsberg, 1920). Setae b , d , and e. are each c h i t i n i z e d , tapered and approximately one and a h a l f times the length of a l l segments combined. Both b and <| are d i s t i n c t l y bent a t about seven-tenths of the i r lengths . Seta b. i s bare or has a few inconspicuous ha irs a long the outer surface of the bent p o r t i o n . Seta <L nas a row of 10 to 30 d i s t a l l y d i r e c t e d , moderately spaced, s imple , s lender spines located a t a p o s i t i o n j u s t proximal to the bent p o r t i o n ( F i g . ^ 2, x—x) . Between f o u r - and seven-tenths of the length of seta e. (the p r i n c i p a l seta) there are two adjacent rows, each of 25 to ho processes ( F i g . ^ 2, s — a ) . 53 Each of these processes (Figs* & h$) has a c h i t i n i z e d frame-work which, i n p r o f i l e , resembles a c a p i t a l "T" standing n e a r l y upr ight or t i l t i n g s l i g h t l y towards the d i s t a l end of the seta ( F i g . M f ) . A body of hyal ine m a t e r i a l l i e s between the d i s t a l extension of the "T" and the body of the seta ( F i g . ¥ f ) . In F i g . **5 the process i s viewed a t an angle perpendicular to the axis of the s e t a . This sketch ( F i g . ^5) shows the outer edge of the process to be broad and near ly s t r a i g h t except for a s l i g h t indentat ion on the upper ( d i s t a l ) sur face . In the male, brownish corpuscles may be found i n the regions where the f i r s t segment jo ins the body, and the second segment jo ins the f i r s t . In the female ( F i g . 1+3) segmentation of the f i r s t antenna Is ind icated by narrow transverse , hyal ine bands. There i s a d o r s a l seta on the second segment which has short ha irs and i s about as long as the capltulum of the f r o n t a l organ. Setae a , b., <jy and & of the male are represented i n the female by four sensory setae , each of which i s h y a l i n e , s carce ly taper ing , rounded a t the t i p , and shorter than the en t i re f i r s t antenna but longer than the f i r s t two segments. Seta e. (the p r i n c i p a l seta) i s about three times the length of a sensory s e t a . I t bears s l ender , moderately spaced, d i s t a l l y i n c l i n e d ha ir s along i t s v e n t r a l surface between one- th ird and three-quarters of i t s l ength . In the female, brownish corpuscles (similar to those in the male) occupy the f i r s t segment and sometimes extend into the second* SECOND ANTENNA* The protopodite and exopodite of the second antenna are similar to those of other species of the genus* The endopodite (see Figs. to **9), on the other hand, shows a few specific characteristics* In the male, the endopodite of the second antenna con-sists of three segments (Fig* k6). Two mammillae are present on the antero-dorsal surface of the f i r s t segment* The pro-ximal mammilla (processus mammillaris) is higher than wide (Fig* ^7, pr* mam*) and the distal mamnlBa is wider than high (Fig* *+7, d* mam*)* When viewed laterally or medially the proximal mammilla seems to be about one-quarter the area (in profile) of the distal mammilla* The proximal mammilla bears setae a and b_ (terms from Skogsberg, 1920)* The second segment bears setae c,, d, e., f, and £ (Figs* K6 & h7). Setae £ and d, are slender spines situated antero-dorsally. Seta e is a small, often inconspicuous spine located at the base of seta X* Setae f and £ are long and terminal; the length of seta £ approximates that of the pro-topodite* Seta £ is longer and more chitinized than f, and is a l i t t l e shorter than the combined lengths of the protopodite and the f i r s t segment of the exopodite* The distal portion of seta X makes a distinct bend and crosses seta £ at about six-tenths of the length of £• Hairs on these two setae, i f 55 present, are sparse and inconspicuous* The third segment (Fig* **7, 3 . ) is swollen at the base and possesses a hook and three sensory setae h., i , and j,. Each seta is hyaline, tapers very l i t t l e , and is about four-tenths as long as seta £• On the right second antenna (Fig* **7) the d i s t a l portion of the hook is about three times longer than the proximal portion (measured between the swollen segment proper and the angle of the hook) and Is dist i n c t l y bowed and terminally cuspidate (Fig. h7, hk.)* On the l e f t limb (Fig. h&) the d i s t a l portion is about four times the length of the proximal, is nearly straight, and possesses faint terminal cuspidation. Both portions of the hook of the right second antenna are longer and more heavily chitinized than those of the l e f t . The endopodite of the female second antenna has only two segments (Fig. ^ 9), the f i r s t of which is similar to that of the male. The second segment bears setae which correspond to those of the second and third segments in the male. Setae c, and & in the male are replaced by a single, d i s t a l l y directed spine i n the female; seta e. appears to be absent or is repre-sented by a small heavily chitinized nob under the base of seta f . Seta f is straight, chitinized, eight-to nine-tenths the length of the protopodite, and possesses a few scattered hairs. Seta £ is straight and slightly longer than the pro-topodite. I t is more heavily chitinized than £ and possesses no hairs. 56 Each of the hya l ine , s carce ly tapering setae Xy a n d 1 i s h a l f the length of seta £ or s l i g h t l y shorter and possesses conspicuous short ha ir s on i t s basa l t h i r d and no ha irs d i s -t a l l y . LABRUM (see P i g s . 50 A 5l)« A p a i r of p a r a l l e l groups of muscle bands running along the v e n t r a l surface of the labrum are de l imited a n t e r i o r l y by one or a few inconspicuous transverse grooves (Pigs . 50 & 5l> g r . ) and p o s t e r i o r l y by a hyal ine p la te ( F i g . 51> p l * ) » The hyal ine p l a t e , which i s f lanked l a t e r a l l y by a p a i r of combs, i s s t r a i g h t or only sha1lowly indented along i t s pos ter ior edge. LABIUM - Paragnath (see F i g . 52, p r g . ) . The labium i s represented by a p a i r of paragnaths attached to the body w a l l on e i ther s ide of the mouth i n such a p o s i t i o n that they might be mistaken f o r an a d d i t i o n a l p a i r of endites of the maxi l lae (see GENUS Conehoecia. above). MANDIBLE, The r e l a t i v e proportions of the f i v e segments of the mandible are not not iceably d i f f e r e n t between males and females, Proximal ly to d i s t a l l y they are the c o x a l , b a s a l , and f i r s t , second and t h i r d endopodial segments. When the proximal par t of the coxale has been c leared of muscles (see F i g . 53)> a k e e l - l i k e process i s seen to be recessed from the proximal t i p of the coxale by a distance almost equal to that along the base of the k e e l . The masticatory endite of the coxale ( F i g . 5*0 possesses three toothed r idges 57 and the mast icatory pad. The r i d g e s , medial to l a t e r a l , are the toothed edge with 10 t ee th , the d i s t a l t o o t h - l i s t wi th 13 to 16 teeth and the proximal t o o t h - l l s t with 10 to 15 teeth* The masticatory pad bears broomlike arrangements of f ine b r i s t l e s , a f a n - l i k e array of coarse b r i s t l e s , and a c r e s t of four hyal ine c o n i c a l spines (Fig* $k, pad)* The basale i s s i m i l a r i n general appearance to that i l l u s -t ra ted f o r Conchoecia eleeans (Fig* 30)* S i tuated antero-d i s t a l l y i s the exopodial appendage which can be recognized by i t s swollen basa l par t and i t s s p i n e - l i k e process* S i tuated proximal ly on the medial surface i s the e p i p o d l a l appendage on which i s born a spine mounted on a c y l i n d r i c a l base of greater diameter than i t s e l f * As usual f or the genus (Skogsberg, 1920, pp* 606 - 7) the d i s t a l end of the basal endite has seven teeth and two heavy spines* S i x of the teeth are i n a rowj the seventh l i e s l a t e r a l to the anter ior three teeth of the row. Four b r i s t l e - l i k e setae occur on the endite and one somewhat d i s t a l l y on the medial surface of the basale proper . The f i r s t segment of the endopodite has four pos ter ior setae and a s ing le a n t e r o - d i s t a l one. The second segment possesses three anter ior and two pos ter ior setae; i t s an ter ior surface i s f r inged wi th short ha irs which become conspicuous a n t e r o - d i s t a l l y . The t h i r d segment possesses seven setae on i t s end and ha ir s on i t s d i s t a l t h i r d . 58 MAXILLA (see F i g . 52). The maxi l la consis ts of procoxa l , c o x a l , b a s a l , and f i r s t and second endopodial segments. T e r -mlnating the endite of the procoxale are nine spines , the two most d o r s a l l y placed possessing conspicuous h a i r s . The t i p of the endite of the coxale i s c l e f t ( this i s not seen from a l l angles) and c a r r i e s three groups of spines* two spines are d o r s a l ; seven or e ight are terminal and d o r s a l to the c l e f t ; and f i v e or s i x are terminal and v e n t r a l to the c l e f t . The basale ( F i g . 52, bas . ) has a s ing le sp ine . The f i r s t endopodial segment bears a row of s i x setae a n t e r i o r l y , a c l u s t e r of three p o s t e r i o r l y , and a rather s tout seta located j u s t d i s t a l to the middle of the medial sur face . On the same segment, a n t e r i o r l y and near the d i s t a l end, are two to four s m a l l , sharply po inted , d i s t a l l y d i r e c t e d , hyal ine sp ines . On the end of the second endopodial segment are two rather s tout c law- l ike setae and three more slender b r i s t l e - l i k e setae . FIFTH LIMB. S i m i l a r i n general appearance to that i l l u s -trated for Conchoecia eleeans ( F i g . 32). The f i f t h limb cons is t s of p r o t o p o d i a l , endopodial and f i r s t , second and t h i r d exopodial segments. Proximal ly on the protopodi te , the v i b r a t o r y p late possesses a d o r s a l lobe with f i v e setae, a middle lobe with f i v e , and a v e n t r a l lobe with four setae . Except for the most d o r s a l l y s i tuated se ta , which i s short and s l ender , a l l the setae possess s lender , p innate ly arranged ha ir s (hairs not i l l u s t r a t e d i n F i g . 32). D i s t a l l y on i t s anter ior 59 surface , the protopodite bears a two-br i s t l ed proximal endite and a t h r e e - b r i s t l e d d i s t a l endite* The endopodite bears four setae with hooked t ips and four with s t r a i g h t ones* Two of the four hooked setae are heav i l y c h i t i n i z e d and two are transparent but may r e f r a c t the chi t inous appearance of the i r heavier neighbours* On the f i r s t exopodial segment two b r i s t l e s are medio-v e n t r a l , f i v e proximo-ventra l , and three are d i s t o - v e n t r a l j one i s m i d - l a t e r a l and one d i s t o - d o r s a l * The medio-ventral spines may be d i sp laced towards the proximo-ventral ones and the m i d - l a t e r a l spine may occur near the d i s t o - d o r s a l * The t h i r d segment i s terminated by three setae of un-equal lengths* SIXTH LIMB* S i m i l a r i n general appearance to those l l l u s -f o r Conehoecia elegans (Figs* 33 & 3*0 • The s i x t h limb possesses f i v e segments with the same homologies as the f i f t h limb* On the protopodite the v i b r a t o r y p la te has a d o r s a l lobe of seven setae, a middle lobe of f i v e , and a v e n t r a l lobe of f i v e setae* Except for the most d o r s a l l y s i tuated s e t a , which i s short and s lender , a l l these setae possess s lender , p innate ly arranged ha irs (hairs not i l l u s t r a t e d i n F igs*)* The endopodite i s de l imi ted by the presence of two slender setae on the knee- l ike bend of the limb* The exopodite consists of four segments and demonstrates 60 sexual dimorphism* That of the male, measured along i t s v e n t r a l edge, i s about one and one- third times as long as that of the female* Proportions of f i r s t , second, and t h i r d segments are re spec t ive ly about 10 s 5 J 7 i n the male, and about 10 $ 7 * 10 i n the female* Except for the one most a n t e r i o r and the three most pos ter ior exopodial setae, a l l setae on the male exopodite are d i s t i n c t l y shorter than those on the female limb* In the male any one of the terminal setae i s almost equal to the v e n t r a l length of the exopodite, whereas i n the female the longest terminal b r i s t l e i s about h a l f as long as the v e n t r a l length of the exopodite* SEVENTH LIMB* The seventh limb consists of two fused segments bearing terminal ly a long d o r s a l seta and a r e l a t i v e l y short v e n t r a l one* PENIS (see F i g * 55), The penis Is almost s t r a i g h t and i s d i r e c t e d more or less v e n t r a l l y from i t s o r i g i n on the l e f t s ide of the body between the seventh limbs and the caudal furcae* I n t e r n a l l y a c h i t i n i z e d duct emerges from the body and enlarges i n the proximal par t of the penis ; i t then narrows and continues towards the t ip* A second c h i t i n i z e d duct emerges from the proximal par t of the penis , runs p a r a l l e l to the f i r s t duct , then jo ins with i t * The junct ion between the two ducts i s indicated by a spot of heavy c h i t i n i z a t i o n jus t d i s t a l to h a l f the length of the penis* The common duct appears to end on the r i g h t s ide a t the t i p of the penis* where an a n t e r i o r l y d i rec ted s p i n e - l i k e p r o j e c t i o n i s s i tuated* Jus t above the sp ine* l ike process and a l s o on the r i g h t s ide of the penis , i s the a n t e r i o r l y d i rec ted copulatory appendage (P ig . 55> ap*) which i s almost as broad a t i t s base as i t i s long* The length of the copulatory appendage i s s l i g h t l y more than h a l f the breadth of the p o r t i o n of the penis to which i t i s attached* S i x to e ight transverse or s l i g h t l y oblique muscle bands are located i n the proximal f o u r - f i f t h s of the penis* CAUDAL FURCA (see F i g * 55)« The caudal furcae are two lamellae which are v e n t r a l l y clawed, apposed to one another, and s i tuated a t the d i s t a l end of the abdomen* Between the furcae i s a p i l o s e depression* Each furca (Fig* 55) bears a s i n g l e , annulated claw followed by seven non-annulated claws* Each claw possesses a double row of sp ine le t s along i t s pos ter ior surface* Pos ter ior to the claws, and p a r t l y Imbedded between the furcae , i s a s ing le (unpaired) b r i s t l e a t l e a s t as long as the s i x t h non-annulated claw* Discuss ion Conehoecia pseudohamata n*sp* i s be l ieved to belong to M i l l e r ' s (1906a) ajajjg-group of the genus Conehoecia. Con- choecia pseudohamata and the prev ious ly known species of th i s group are character ized by having more than one group of l a t e r a l glands on a t l e a s t one valve of the s h e l l * Mul ler (1906a & 1906c) included f i v e species i n the groups C* 62 n » n leptothrix Muller, C. valdlviae Muller. C. hettraca Muller, C. tt ^ » beleicae Muller, and C. a lata Muller. Conchoecia leptothrix and C. valdlviae were regarded by tt Muller (1906a) as being "isolated"; but he retained them within the group for want of better classification. He regarded C. hettraca and C. beleicae as being more closely related to one another than to C. alata (Muller, 1906a & 1906c). Conchoecia hettraca and C. beleicae are related morpholo-gically by possessing lateral gland-groups only on the l e f t valve and by having peg-like processes on the principal seta of the male f i r s t antenna. In a similar way C. alata and C. pseudohamata would seem to be related i n that both have groups of lateral glands on both l e f t and right valves, and similar processes, superficially "T"-shaped in p r o f i l e , on the prin-ci p a l seta of the male. The above evidence suggests that C. a lata is related to C. pseudohamata about as closely as C.. hettraca i s to C. beleicae. Conchoecia pseudohamata and C. alata di f f e r morphologically In at least three features: the number of lateral gland-groups per valve of the shell, the relative prominence of the ridges forming the shoulder vault of the shell, and the detailed structure of the processes on the principal seta of the male f i r s t antenna. Conchoecia pseudohamata has three or four (usually four) groups of la t e r a l glands per valve; C. alata i s stated, by Muller (1906a), to have only three. Although 63 undescribed, v a r i a t i o n i n the number of groups of l a t e r a l glands of C. a l a t a may occur. I f this were so, the number of groups of l a t e r a l glands per valve would be limited i n i t s value as a diagnostic character. Ridges of the shoulder v a u l t i n Conehoecia a l a t a extend l a t e r a l l y to form wing-like processes which end suddenly i n the posterior h a l f of the s h e l l (Muller, 1906a). In C. pseudo- hamata these ridges neither extend beyond the normal width of the s h e l l nor end suddenly i n the posterior h a l f . The shape of the s h e l l seems to be d i s t i n c t and diagnostic for the two species. The wing-like extension of the s h e l l of C. a l a t a , however, could possibly be a f l o a t a t i o n mechanism induced by some environmental factor r e l a t e d to the v i s c o s i t y of water i n i t s environment. Since the s h e l l of the ostracod has not been shown to a l t e r according to such environmental conditions (Skogsberg, 1920), and has long been used as the sole feature f o r i d e n t i f y i n g f o s s i l forms, i t must be ten-t a t i v e l y considered as a v a l i d diagnostic feature. The other two diagnostic features separating Conehoecia  pseudohamata from C. a l a t a are not l i k e l y to a l t e r , or be al t e r e d by, buoyancy. These ares the number of groups of l a t e r a l glands on the s h e l l , and the detailed structure of the processes of the p r i n c i p a l seta of the f i r s t antenna of the male. In both species the chitinous framework of each of the processes on the p r i n c i p a l seta of the male f i r s t antenna i s 6h of nT"~shaped p r o f i l e . Despite th is s i m i l a r i t y , however, these processes are d i s t inc t ly d i f f e r e n t for the two spec ies . Mul ler (1906a) describes the "T"-shaped framework of the process i n Conehoecia a l a t a as being l i k e a ttmushroom cap" bounded by two de l i ca t e membranes which produce "apparent wing- l ike widenings" of i t s stem. In h i s f igure (Mul ler , 1906a, F i g . 7> P I . XXIX) , the shape of each membrane i s convex and would appear to enclose hyal ine m a t e r i a l . In C . pseudohamata. on the other hand, the framework resembles a "bracket fungus" (see F i g . *+5)> bounded only on i t s d i s t a l s ide by hyal ine m a t e r i a l ; a membrane, i f present , appears to be too d e l i c a t e to d i s t i n g u i s h . Although the d i f ference i n shape of the chi t inousframework may have been a matter of i n t e r p r e t a t i o n , the d i f ference i n d i s t r i b u t i o n of the hyal ine mater ia l seems d i f f i c u l t to d i s p u t e . Alone the "T"-shaped framework gives the appearance of a hook ( L . hamata ~ hook)} but , with the hyal ine m a t e r i a l , th is impression i s shown to be f a l s e ( L . pseudo - f a l s e ) , hence the s p e c i f i c name, pseudohamata. Taken together the di f ferences i n the three features « • the shape of s h e l l , the number of groups of l a t e r a l glands, and the s tructure of processes of p r i n c i p a l seta of the male f i r s t antenna — seem to provide an adequate basis for d i s -t ingui sh ing between Conehoecia a la ta and C . pseudohamata. This opinion was supported by J . P . Harding of the B r i t i s h Museum (Natural H i s t o r y ) who, i n a personal communication, wrote "The di f ferences you mention seem to me quite s u f f i c i e n t to prevent your specimens being named C,. a l a t a " . 65 D i s t r i b u t i o n Conchoecia a l a t a has been c o l l e c t e d from the A t l a n t i c Ocean between 25° 35* N . (Barney, 1921) and 30° 06* $ . (Mul ler , 1906a), i n the Indian Ocean north of k° 05* S . (Mul ler , 1906a, and Cannon, 19^ 0), and i n the P a c i f i c (Tchindonova, 1959) from e i ther the Kurile-Kamchatka reg ion or fur ther south (exact l o c a t i o n not g iven) . The d i s t r i b u t i o n of C , a l a t a i n the A t l a n t i c i s f a i r l y w e l l known (Mul ler , 1906a; Barney, 1921} and l i e s , 1953) and appears to be l i m i t e d between 30° N . and 30° S. Conchoecia pseudohamata has been c o l l e c t e d between h9° and 50° 53* N . from various i n l e t s on the coast of B r i t i s h Columbia (see F i g . 61, under Region) and from the Ocean Weather S t a t i o n "P", a t 50° 00* N . , 1^ 5° 00« W. These are the only known records , however, and are I n s u f f i c i e n t f or est imating the l i m i t s of geographic d i s t r i b u t i o n . GROWTH S T A G E S 66 In the present study growth stages have been numbered from one to seven, the adu l t being the f i r s t stage. A d d i t i o n a l numbers, e i gh t , n ine , e t c , could be added to accommodate younger stages should they be found. Fowler(1909) used a s i m i l a r system, but began the ser ies with the stage preceding the a d u l t , thus g iv ing the adu l t no number. Inc lus ion of the a d u l t , however, seems more reasonable s ince th i s stage does not d i f f e r apprec iably i n form from those preceding i t . In Indian Arm, where only two species of the genus Conehoe- c i a are found to e x i s t , the growth stages of Conehoecia elegans can be recognized by (1) the attenuate shape of t h e i r s h e l l s , (2) the absence (present only r a r e l y ) of a p a i r of p a p i l l a e (rudimentary claws) and a s ing le (unpaired) b r i s t l e succeeding the l a s t p a i r of f u r e a l claws ( F i g , 56), and (3) a p r o p o r t i o n a l r e l a t i o n s h i p between the s i ze of the s h e l l and the number of f u r e a l claws (see below, ret F i g , 58)* Inc luding the a d u l t , seven stages of growth for th i s species have been found i n Indian Arm, Only two specimens represent ing each of the smal les t two stages were a v a i l a b l e and, although the s i ze i n -dicates that they belong to C , elegans. the i n d i c a t i o n of a p a i r of p a p i l l a e (rudimentary claws) puts th is choice i n doubt. F igure 58 i l l u s t r a t e s the approximations of s h e l l length that helped d i f f e r e n t i a t e growth stages of Conehoecia elegans from those of the other Indian Arm species* Any p a r t i c u l a r 67 stage of growth was defined by the number of claws on each of I ts caudal furcae , and the species to which l t belonged was determined by i t s having a c e r t a i n s i ze i n r e l a t i o n to that of the comparable stage i n the other spec ie s . As noted above the two species could a l s o be d i s t inguished by the shapes of t h e i r she l l s and the absence or presence of a p a i r of p a p i l l a e and a s ing le b r i s t l e on the caudal furcae* Figure 59 shows that the l a t e r growth stages of Conchoecia  elegans have a tendency to become d i f f e r e n t i a t e d in to large and smal l forms, u l t imate ly to become, r e s p e c t i v e l y , male and female* Usua l ly i n the seven-clawed stage (stage 2) the male can be Ident i f i ed by a rudimentary penis and larger s i z e ; and the female by a ye l lowish c l u s t e r of eggs and smaller s i ze* Since the colour of the abdomen Is often s i m i l a r to that of the eggs, however, the immature female cannot always be defined with cer ta inty* Occas ional ly a d i s t i n c t l y large form may have no penis apparent, or a moderately large form may bear a c l u s t e r of eggs* No attempt was made a t sex determination of specimens of stages smaller than this seven-clawed stage* The growth stages of the other spec ies , Conchoecia p s e u d o - hamata. can be Ident i f i ed by the rather broad s h e l l , the pre -sence of a p a i r of p a p i l l a e (rudimentary claws) fo l lowing the l a s t p a i r of developed f u r c a l claws ( F i g . 57)> and by a p r o p o r t i o n a l r e l a t i o n s h i p between the s i ze of the s h e l l and the number of f u r c a l claws ( F i g . 58)* An unpaired b r i s t l e , 68 sandwiched between the furcae, and posterior to their claws, is found occasionally in the stage having four fureal claws, usually in that having five claws, and always in those possessing six to eight furcal claws* Including the adult, seven stages of growth were found* In Conehoecia pseudohamata. unlike in C* elegans. the adult female is larger than the adult male* Although no size differentiation is obvious in the seven-clawed stage (stage 2) of C* pseudohamata. this stage may be readily sexed by means of the rudimentary penis found in the immature male and the cluster of eggs in the female* No attempt was made at sex determination of specimens of stages smaller than this seven-clawed stage* A few subadult growth stages resembling Paradoxostoma  striungulum Smith were found* These, however, were not in a continuous series and could not be definitely identified with the adult* Philomedes sp* was represented only by a single adult male specimen* Factors (called "growth factors" by Skogsberg, 1920) representing the increase of shell length from one stage to another, are presented in Table 2, along with the means of shell length from which they were calculated* Conehoecia  elegans and C. pseudohamata are represented in this table* Examination of these growth factors for Conehoecia  elegans shows the differentiation of shell length with regard 69 to sex* During the molt from third to second stages the length of the male shell increases more than does the length of the female shell (Table 2)* From the second to f i r s t stages, however, this increase is slightly less than in the female* It may be noted (Table 2) that the growth factors for the earliest and latest molts of Conchoecia eleeans are unusually small* In the stages of early development this can be partly attributed to the shell being somewhat globular and not ex-pressing i t s aHover size by length measurement alone* In later stages measurements of length become more nearly in-dicative of general size* The factor for growth between stages one and two, which have similar length to height ratios (about 2*1), appears to be unusually small* This may perhaps be due to an increased proportion of the energy of anabolism being contributed to the attainment of sexual maturity and thus sacrificing increase i n size. In Conchoecia pseudohamata sexual dimorphism in shell length becomes apparent only at the latest molt, and is char-acterized by the female shell growing larger than that of the male* Following the earliest known molt, which has a rather small growth factor, is a series of molts having progressively greater factors* This may be due to the gradual elongation of the shell as i t changes with age from a globular to an angular shape* As i n C* eleeans. there is a small growth factor between stages two and one* Again, this may be indicative of the sacrifice of potential size for the attainment of sexual maturity. 70 REGIONAL VARIATION i n Conehoecia elegans Sars and Conehoecia pseudohamata n . sp . Plankton samples c o l l e c t e d from various i n l e t s of B r i t i s h Columbia were examined for ostracods* In a d d i t i o n , ostracod samples from the Ocean Weather S t a t i o n "P1* were Inspected for specimens of Conehoecia elegans and C . pseudohamata. In samples from l i b e r a l , T o f i n o , Herbert , and Saanich I n l e t s , the only species found was C . elegans; i n those from Bute, Knight , and Muchalat i n l e t s , two species were d iscovered, C . elegans and C . pseudohamata. Ostracods from the weather s t a t i o n "P t t contained one male and one female of C . pseudohamata. At l e a s t f i v e males (four i n one case) and f i v e females of each species present were removed from each i n l e t sample and measured for s h e l l length (Figj. 60 & 6 l ) . The s h e l l length for each populat ion sampled has been estimated as a mean, a range, an I n t e r v a l of one standard error on e i ther s ide of the mean, and an I n t e r v a l of three standard deviat ions on e i ther s ide of the mean. The l a t t e r i n t e r v a l approximates a 99$ confidence i n t e r v a l . Symbols represent ing parameters i n F i g s . 60 & 61 are the same as those used i n F i g . 58 . In F i g . 6 1 , In a d d i t i o n to parameters of the i n l e t populat ions , s h e l l measurements of the male and female from the weather s t a t i o n are presented. A male of each species present was taken from each i n l e t sample, d i s sec ted , and examined for d iagnost ic features( for 71 diagnoses see above under C l a s s i f i c a t i o n ) . The male and female specimens from S t a t i o n ttP" were treated i n this manner. Every specimen examined, inc lud ing those from S t a t i o n "P", conformed w e l l to the r e s t r i c t i o n s imposed by the appropriate d iagnos i s . The overlapping of confidence i n t e r v a l s f or the s h e l l lengths seems to ind icate that , for each spec ies , l i t t l e d i f -ference ex i s t s between populations with regard to the various i n l e t s i n which they occur. S h e l l lengths f o r the specimens o f Conchoecia pseudohamata from S t a t i o n M P M , o n the other hand, f a r exceed the upper l i m i t s of confidence for the forms found i n the B . C . i n l e t s . This suggests the p o s s i b i l i t y of a d i s t i n c t "oceanic1* popula t ion . Whether the d i f ference i n s i z e i s due to genetic or environmental e f fec ts i s unknown. P A R T n E C 0 L 0 G Y INTRODUCTION 73 A t present the ecology of the marine planktonic ostracods i s r e c e i v i n g much less a t t e n t i o n than that of the marine benthonic ones. E c o l o g i c a l information on the Recent o s t ra -cods of the benthos i s used as a basis f or i n t e r p r e t i n g the paleoecology of t h e i r f o s s i l r e l a t i v e s . A f a i r l y complete review on the ecology of ostracods, e s p e c i a l l y of marine benthonic forms, i s given by Benson (1959)• B i o l o g i c a l information on the marine planktonic ostracods may be found i n Mul ler (1893, 189*0, Skogsberg (1920), Sars (1928), Ostenfeld (1931), and Elof son (19^ 1). Publ icat ions by Ostenfeld (193D, Skogsberg (1920), Sars (1928), and Elo f son (19^ 1) as w e l l as Jesperson (1923), Davidson (192h), Stephensen (19M-3) and Kie lhorn (1952) contain notes on the ecology of Conchoecia elegans S a r s . one of the species from Indian Arm. Conchoecia elegans was recognized by Mul ler (1927) and Elofson (19*4-1) as a cosmopolitan spec ies . I t has been reported to occur i n the A t l a n t i c Ocean from 79° 58* N . to 55° S . (Skogsberg, 1920), i n the Indian Ocean from 13° 2* N . to 27° 58* S . (Mul ler , 1906a), and i n the western P a c i f i c Ocean a t 0° 17* S . , 129° 1MB, and h° 30' S , 128° 20 E . (Mul ler , 1906b, p.37)« I t has a l s o been reported from the eastern P a c i f i c i n the reg ion of Vancouver I s l a n d , B r i t i s h Columbia (Smith, 1952). 7h Conehoecia elegans Sars and C, pseudohamata n. sp. are abundant i n the plankton of Indian Arm. Conehoecia elegans occurs a l s o i n at l e a s t seven other B r i t i s h Columbia i n l e t s ; i n three of these C,. pseudohamata i s present (see F i g s . 60 & 6l under Region). These occurrences indicate that Indian Arm i s not unusual with regard to i t s planktonic ostracods. Previously Indian Arm was studied with regard to the prod u c t i v i t y of i t s phytoplankton (Gilmartin, i960). A r e l a t i v e l y thorough treatment of the synoptic oceanography of the i n l e t accompanied this study. The pro d u c t i v i t y was estimated to be at l e a s t as great as found over the coastal shelf of the same geographic region. The present study i s the f i r s t contribution toward a knowledge of the d i s t r i b u t i o n of zooplankton i n Indian Arm. I t i s concerned with d i u r n a l and seasonal changes i n the d i s -t r i b u t i o n of the two planktonic ostracods, Conehoecia elegans Sars and C. pseudohamata n. sp., found i n this i n l e t . These d i s t r i b u t i o n s were studied i n r e l a t i o n to the possible e f f e c t s of oceanographic factors and penetration of l i g h t . An inves-t i g a t i o n of the importance of transport of these ostracods i n t o and out of the i n l e t has been considered a supplement to the main in v e s t i g a t i o n . The study gives a general coverage of several aspects of the d i s t r i b u t i o n s of these ostracods. The re s u l t s were of an exploratory nature. They implied c e r t a i n relationships between the environment and the biota, and provided foundation f o r 75 several hypotheses which should be tested i n the future by more specific methods than those used in the present inves-tigation. An examination of the distributions of the oceanographic factors temperature, s a l i n i t y , and oxygen content — revealed that water from outside had entered the deeper stra-ta of the i n l e t during the early months of I960, Populations of both species showed some up-inlet movement during this period. This movement may have been related to conditions produced by the intruded water. Seldom was either species found near the surface. Perhaps the thermocline or halocline was a barrier to migration into the surface layer. Diurnal ve r t i c a l migration differed for the two species. In the upper and intermediate depths, Conehoecia elegans migrated upward at night, whereas at greater depths i t showed no definite diurnal movement. In the upper part of the water column C, pseudohamata tended to migrate upward at night, whereas at intermediate and lower depths, i t usually migrated downward. Light was considered as a factor causing downward movement that occurred during the day. Although several features suggested that light was the dominant factor, no direct relationship was found between the amount of light penetration and the extent of vertical migration of the or-ganisms « 76 METHODS COLLECTION OP DATA The narrowness of Indian Arm and the large s i ze of the vessels usua l ly ava i l ab l e l i m i t e d the choice of s tat ions to those l y i n g along the mid - l ine of the i n l e t . Stat ions se lected were 2, 6, 9, 12, 15* and 23 (see F i g . 62). These were chosen to provide a representat ive coverage of the b i o l o g i c a l and oceanographic condit ions of the i n l e t . For example, Stat ions 6 and 9 were located over the deep b a s i n , and Stat ions 2 and 12 were u p - i n l e t and down-inlet from the bas in ; Stat ions 15 and 23, chosen to detect exchanges of water between Burrard I n l e t and Indian Arm, were located , r e s p e c t i v e l y , w i t h i n and over the s i l l a t the mouth. During each of 10 cruises i n I960, S ta t ions 2, 6, 9, and 12 were sampled four times during each of two 2*f-hour p e r i o d s . Whenever p o s s i b l e , Stat ions 9, 12, 15, and 23 were sampled during consecutive f lood and ebb tides i n an attempt to inves-t igate the e f fects of t i d a l exchange. In J u l y , a smal l ve s se l was ava i l ab l e and i t was poss ib le to sample the shallower water on e i ther s ide of the mid- l ine of the i n l e t . For this purpose, secondary s tat ions to the east and west of Stat ions 2, 6, and 12 were occupied i n d a y l i g h t . Those on e i ther s ide of Stat ions 2 and 12 were over water about 80 m. deep; those on e i ther s ide of S t a t i o n 6 77 were over water about 160 m. deep. Oceanographic data were c o l l e c t e d a t Stat ions 2, 6, 9, and 12 near mid-night and noon, and a t Stat ions 9, 12, 15 and 23 during large r i s i n g and f a l l i n g t i d e s . Water samples and temperatures were taken from standard depths of 0, (5)1, 10, 2G , 50, 75> 100, 150, and 200 m. Sub-surface l i g h t was measured along with the oceanographic data c o l l e c t e d during the day. Readings were taken a t one-half metre below the surface and a t f i v e metre i n t e r v a l s from the surface to the depth of no detectable l i g h t . Plankton was c o l l e c t e d immediately down-Inlet from a l l oceanographic s tat ions except S t a t i o n 12, where shoal ing necess i tated the procurement of samples from over the s t a t i o n p o s i t i o n i t s e l f ( F i g . 62, h o r i z o n t a l b a r s ) . Depths of sam-p l i n g were a t 30 m. Intervals from surface to bottom at Stat ions 2, 6, 9, and 12, but a t 25 and 20 m. in t erva l s a t the shallower stations,15 and 23 r e s p e c t i v e l y . A t Stat ions 6 and 9, a delay of about *+0 minutes occurred between the sampling of plankton from the top four and the bottom three depths. Temperatures were obtained using Richter and Wiese revers ing thermometers. Water samples were c o l l e c t e d with A t l a s water b o t t l e s . S a l i n i t y was determined by t i t r a t i o n Depth of 5 m. not sampled i n January, March, and May. of 10 ml, samples with silver nitrate, following the Mohr method (Strickland and Parsons, 1961). Oxygen content was determined only for samples from Station 6j 50 ml* portions of samples were titrated using the standard Winkler method. (Strickland and Parsons,1961). Light energy was recorded by two Weston photo c e l l s * One, the deck-cell, remained on deck and was compared with the sea-cell, which was lowered into the water from a boom seven metres long, designed to keep the c e l l away from the shadow of the ship. Readings from both cells were taken within 30 seconds of one another from a micro-ammeter having a mechanical pointer-type indicator. This combination of cells and micro-ammeter responds to wave-lengths of the visible spectrum and is limited to a sensitivity of 10",lf langlies/minute (Strickland, 1958)* Calibration was against an Eppley pyrheliometer (which responds to a spectrum wider than that of visible light) at light intensities of 0.01 to 1*0 ly./mino As a result of calibrations, readings of 100 and 600 micro-amperes on the Weston photometer were estimated to be 10~2 and IO- 1 ly*/min., respectively* From Strickland's (1958) estimation of the limit of sensitivity for a Weston c e l l , the smallest distinct reading, 0*1 micro-amperes, was taken to be 1CT^ ly./min* Zooplankton was collected using Clarke-Bumpus plankton samplers (Clarke and Bumpus, 1950) modified according to Paquette and Frolander (1956)* Samplers were towed horizon-t a l l y at the desired depths for 15 minutes at a speed of about 7 9 29h knots. (They were opened and closed by messengers.). From 800 to 1000 l i t r e s (8 to 10 m.3) of sea-water were f i l t e r e d over a distance of about 1 km., the actual volume f i l t e r e d being calculated from the number of counts recorded by a flow-meter i n the mouth of each sampler. An extensive program was carried out to calibrate these flow-meters and to test for differences between individual samplers and for the effects of the different sizes of mesh used in their nets. A f u l l report is presented in Appendix I. For the present study, the volume f i l t e r e d may be calculated from a calibration value of h-0 l i t r e s per count of the flow-meter. The differences between meshes and between samplers were considered to be insignificant in relation to differences between concentrations of plankton and, therefore, were not accounted for in calculating these concentrations. During the cruises up to and including that of May, only nets of 0.^0 mm. mesh size were used on the samplers. Sub-sequently, nets of this mesh were used for one of the 2*f-hour periods of sampling and nets of mesh size 0.12 mm. were employed during the second 2\ hours. DATA EXAMINED Oceanographic data and plankton collections were available i n excess of what could be examined in the time available; 80 therefore, i n order to provide an adequate coverage of the seasonal changes during one year i n the inle t , a selection was made. Some of the data chosen were collected from Stations 2, 6, 9, and 12 during the hours closest to midnight and noon* These in turn were selected from one of the two 2H*.hour periods of sampling which took place during the cruises of January, March, May, July, September, and November, I960* When i t was necessary to confirm findings or add to information from these selected materials, reference was made to data from other cruises and from other 2*+~hour periods of sampling. Stations 15 and 23 were chosen for examination of the exchange of ostracods between Indian Arm and outside water. To preserve uniformity, samples examined were usually those collected with nets of 0,h0 mm. mesh size; however, to complete the picture of diurnal vertical migration, some collections made with nets of 0.12 mm. mesh size were included. TREATMENT 0F; PLANKTON SAMPLES The small numbers of specimens available from Stations 15 and 23 allowed the examination of entire samples. The larger numbers collected from other stations, however, necessitated restricting the examination to a subsample. A representative 1C$ portion of each sample was drawn off by use of a vacuum assisted subsampler, the design and use of which are described i n Appendix I I . A comparison of the relative amounts of 81 variation due to subsampling, sampling and population difference is presented in Appendix III* This comparison shows that subsampling variation is less than sampling variation, con-siderably less than variation due to population difference and, therefore, not li k e l y to mask any important fluctuations i n concentration within a population* Another comparison i n Appendix III indicates that subsampling variation may obscure a l l but the largest differences in the proportions of the various growth stages found i n a single sample* Ostracods were removed from each subsample and sorted to species and growth stage* Specimens were checked against the diagnostic features and the measurements of shell length appropriate to the species and growth stages to which they were designated* Adult females of samples from Station 9 were examined for the relative maturity of their eggs* Immature eggs were recog-nized by their translucence and smaller size, and mature eggs by their opaqueness and maximal size* The relative maturity represented by each sample was estimated by the proportion of females in a subsample which had most of their eggs opaque* The number of Individuals representing each stage was counted and recorded* By dividing the number of individuals of the 10$ subsample by one-tenth of the appropriate reading (counts) recorded by the flow-meter of the Clarke-Bumpus sampler, the number of individuals captured per count may be estimated. Since one count represents ^0 l i t r e s of sea-water 82 f i l t e r e d , the number of i n d i v i d u a l s per count equals the con-centra t ion i n i n d i v i d u a l s per kO l i t r e s . A l l the above i n -formation was transferred to a punch-card (key-sort) system so that the data for each sample could be r e a d i l y located with reference to the month, day, hour, p lace , or depth of c o l -l e c t i o n * DISTRIBUTION OF OCEANOGRAPHIC FACTORS Physiography may be considered an important fac tor I n f l u -encing the oceanography of Indian Arm* Indian Arm (Fig* 62) i s about 22 ki lometres i n length and s l i g h t l y more than one ki lometre i n average width; i t s depth i s about 200 m* over the middle three-quarters of i t s length and about 30 m* over the s i l l a t i t s mouth. I t l i e s roughly north-south; south-wardly i t jo ins Burrard I n l e t , which i n turn connects with the S t r a i t of Georgia . With the poss ib le exception of the depth of the s i l l , the physiography of Indian Arm may be regarded as s i m i l a r to the physiographies of most B r i t i s h Columbia i n l e t s ; the s i l l i s shallower than average, but not the shallowest (Gi lmart in , I960). Fresh water i s added through r i v e r and p e r i p h e r a l stream r u n - o f f , and by p r e c i p i t a t i o n ; sa l ine water from outside ( S t r a i t of Georgia) may enter by way of Burrard I n l e t over the s i l l (Gi lmart in , I960). Such addit ions of water as these would be compensated by loss of water i n t o Burrard I n l e t . 83 With regard to this exchange, the s i l l depth is considered an important factor. In i960, below a shallow thermocline and halocline, temperature ranged from 7 to 9° C.; salinities from 26 to 27 °/oo$ and dissolved oxygen values from 3 to 5 mg./l. The distributions of temperature, salinity, and dissolved oxygen were examined to detect those changes in the oceano-graphic environment which might have been related to changes in the distribution of ostracods. In indication of a major oceanographic change between January and May prompted examination of data from February and April in addition to those data already selected. Temperature was shown to have its greatest vertical gradient within the upper 10 m. In this part of the thermo-cline, the range of temperature fluctuated seasonally from less than 1 C.° to as much as 10 C.° The seasonal change in temperature distribution below the thermocline is shown in Fig. 63, where isotherms are plotted against depth on longitudinal profiles of Indian Arm. A lowering of the temperature of the intermediate and deep water was observed during the period from February to May (Fig. 63)• This cooling was probably a result of relatively high salinity water, cooled from outside, having sunk into Indian Arm} water cooled at the surface within the inlet was of low salinity and therefore too buoyant to sink. Qh A progressive u p - i n l e t movement of the intruded water i s indicated by a month-to-month displacement of the isotherms between the warm resident water and the cold f o r e i g n water. The 7»6 °C» isotherm, f o r example, i s considered to represent f o r e i g n water which has been w e l l d i l u t e d with resident water. In March this isotherm was steeply t i l t e d upward toward the mouth of the inlet} i n A p r i l i t was moderately t i l t e d upward toward the mouth} and i n May i t was only s l i g h t l y t i l t e d toward the mouth. This gradual l e v e l i n g of the isotherm suggests that mixing was occurring h o r i z o n t a l l y . The f a c t that the l e v e l i n g progressed i n the up- i n l e t d i r e c t i o n indicates that mixing was extending toward the head. The gradient of s a l i n i t y was greatest i n the upper 10 m; i t s range was as l i t t l e as 5 °/oo to as great as 15 °/oo i n 10 m. The d i s t r i b u t i o n of s a l i n i t y during the year i s shown i n F i g . 6*f by isohalines p l o t t e d against depth on longitudinal p r o f i l e s of Indian Arm. An approximation of the s a l i n i t y near the bottom of the i n l e t i s inserted i n each p r o f i l e . In January the s a l i n i t y a t the bottom was 27*0 °/oo} i t increased to about 27.3 °/oo by A p r i l , and decreased gradually to approximately 27.1 °/oo by November. A corresponding trend was shown by a r i s e and f a l l i n the depth of the 27 °/oo i s o h a l i n e . This isohaline was at the bottom i n January, a t about 65 m. i n February, and at about 15 m. by March. During l a t e r months i t returned to deeper l e v e l s , occurring between 100 and 150 m. i n November (Fig. 6*0. The increase i n s a l i n i t y seems to have been caused by the addition of higher s a l i n i t y 85 water during the period between January and May. Such water must have entered from Burrard Inlet* The period over which sali n i t y increased coincided with the period during which temperature decreased. Such changes i n the temperature and sal i n i t y may be expressed by an increase i n density. In F i g . 65 the average density (expressed as the anomaly of density, 6^.) in the lower half of the water column at Station 6 i s plotted for the various months for which data were examined. Density is shown to have increased from January to A p r i l and gradually decreased thereafter (Fig. 65)» Thus, during the earlier part of the year, temperature and sa l i n i t y changes were reflected by changes in density. The higher density of the foreign water would account for i t s having sunk to the deeper levels of the i n l e t . Oxygen content of the water at the surface was observed to be always higher than in the deeper water (Fig. 66). Oxygen sol u b i l i t i e s appropriate to the existing surface tem-peratures and s a l i n i t i e s were obtained using the nomogram of Richards and Corwin (1956)j these were presented in Fig.66 as small c i r c l e s . Comparison of the observed oxygen con-centrations with the s o l u b i l i t i e s obtained from the nomogram indicates 'that the oxygen content of the surface water exceeded solu b i l i t y from May to September. Probably photon-synthetic ac t i v i t y was maximal during this period (Gilmartin, i960) and was rapidly producing oxygen. A decrease in the mean oxygen concentration in the upper 86 stratum (0-65m.) was observed i n February. This decrease suggests that the water of lower oxygen content, observed i n the deeper strata i n January (Fig. 66), may have been displaced upward and, by February, had become mixed with the water of the surface stratum. The average oxygen concentrations of the intermediate (65 - 125 m.) and deep (125 - 200 m.) s t r a t a showed a sub-s t a n t i a l increase between the January and February c r u i s e s . The concentrations r e s u l t i n g from this increase did not vary appreciably during the following few months but, from May to November, they showed a gradual decrease. The increase between January and February, being i n the deeper s t r a t a , would have been independent of atmospheric exchange and photosynthetic a c t i v i t y which might have increased the oxygen a t the surface i n Indian Arm. Additional oxygen, therefore, must have been transported by water which entered the i n l e t from outside. Examination of the d i s t r i b u t i o n of oceanographic factors indicates that, during the period from January to May of I960 , water from outside flowed into the deeper leve l s of Indian Arm. This water was of lower temperature and higher s a l i n i t y (and therefore of higher density), and also had a higher content of oxygen than the water previously resident i n Indian Arm. Similar intrusions into Indian Arm have been observed i n the past. One which occurred i n 1957 "...appears to have v i r t u a l l y flushed...." the i n l e t , whereas another i n 1959 seems to have been more limited (Gilmartin, i960). Even 87 though the resident water appears to have been replaced, "flushing 1" did not necessarily occur. Water may have been exehangedin small amounts rather than i n a sudden mass replacement* The intrusion of foreign water could have affected the distribution of ostracods inhabiting Indian Arm; i t could have also recruited ostracods from an outside source* The importance of each of these possibilities is discussed below under Longitudinal Distribution:;, TIDE Tidal curves and times of occupation of stations are shown in Figs, 67 and 68. The greatest rise in tide coin-cident with collection of data occurred in March, Lesser rises took place during the January, A p r i l , and November observations, and f a l l i n g tides were present during observations of the other months. As shown in Figs* 63 and 6k the amount of foreign water present in March appears to have been considerably greater than during the other months* Part of this increase may have been a temporary occurrence dependent oh the presence of the previously mentioned (large1' rise in^tild'e1* Figure 69 indicates that the temperature and sal i n i t y distributions differed between this large rise, and the smaller rises that occurred 88 about twelve hours before and twelve hours a f t e r ( F i g . 6 7 , March 23 and 2^) . During the smaller r i s e s , the t i d a l influence on tem-perature seems to have been f e l t about as f a r as S t a t i o n 9} during the larger r i s e , i t appeared to have approached St a t i o n 6 ( F i g . 6 9 ) . In the down-inlet region of the i n l e t , isohalines were i n c l i n e d u p - i n l e t and were more steeply sloped during the larger r i s e i n tide than when the smaller r i s e s were present. The slope of isohalines indicates that resident water may have been displaced downward and u p - i n l e t by the foreig n water. This displacement appears to have been greater during the larger r i s e . The e f f e c t s of tide may not always be as evident as those observed i n March fo r the large r i s e . During this period, water moving i n t o the region was well characterized by i t s temperature and s a l i n i t y . Perhaps on other occasions the e f f e c t would be j u s t as great but not as e a s i l y recognized. Smaller e f f e c t s , related to lesser tides and too small to be r e a d i l y noticeable, may eventually produce a s i g n i f i c a n t additive e f f e c t . Although tide i s probably an important mechanism by which water can be exchanged between Indian Arm and outside, several other factors may influence this exchange. Ostracods may have been transported with water exchanged between Indian Arm and Burrard I n l e t . In this regard, the e f f e c t of tide i s considered. 89 LIGHT Light measurements were taken for comparison with the ve r t i c a l distribution of ostracods. Because the amount of light varies so widely within short periods (as a result of changes in cloud cover, sea condition, turbidity, etc.) no attempt was made to establish i t s seasonal trend. For this reason a generalized comparison was not considered. Instead, li g h t was measured within an hour of each daylight plankton collection to provide material for direct comparison of light penetration with the vertical distribution of the ostracods. Throughout the year, light energy of 10"" l f langlies/minute was transmittable to depths of 30 to 60 m. when the sun neared Its maximal altitude. The depths of penetration of various levels of light energy (IO""1, ICT 2, and 1 0 " l f ly./min.) into the water at Stations 6 and 9 are plotted i n Fig. 7 0 . These plots are to be compared with those for the depths attained by the ostracods in their downward migrations. DISTRIBUTION OF OSTRACODS Several aspects of the distribution of Conehoecia elegans Sars and C. pseudohamata n. S P . have become apparent. These are expressed i n graphical form in Figs. 71 to 88 and are discussed under three headings: vertical distribution, transverse distribution, and longitudinal distribution. 90 VERTICAL DISTRIBUTION To express the extent of d i u r n a l v e r t i c a l migrat ion of the two species a t d i f f e r e n t times of the year , depths of q u a r t i l e s of the v e r t i c a l d i s t r i b u t i o n s have been ca l cu la ted and p l o t t e d (Fig*. 71 & 72). The depth of d i s t r i b u t i o n as expressed by the depth of th is s t a t i s t i c would seem less l i k e l y to be inf luenced by seasonal change i n populat ion dens i ty than i f l t were expressed as the depth of some chosen concentration* Depths occupied by the f i r s t , second, and t h i r d q u a r t i l e s have been p lo t t ed f o r the v e r t i c a l d i s t r i b u t i o n s occurring a t n i g h t and during day l ight i n January, March, May, J u l y , Sep-tember, and November* The depth of the f i r s t q u a r t i l e repre -sents that p o s i t i o n i n the water column above which there were 25$ of the organisms and below which there were ! % • S i m i l a r l y the depth of the second q u a r t i l e (median) i s where 50$ of i n d i v i d u a l s were above and 50$ below; that of the t h i r d quar-t i l e i s where 7% were above and 25$ were below. The v e r t i c a l d i s t r i b u t i o n s of the various growth stages of the two species are shown by a ser ies of graphs (Figs* 73 to 76) represent ing samples taken i n J u l y from S t a t i o n 9 a t various times over a three-day period of c l ear skys and s table l i g h t condit ions* The axis of concentrat ion on each graph represents the number of i n d i v i d u a l s of a l l stages per 1+0 l i t r e s of sea water* Concentrations are d iv ided to show the 91 r e l a t i v e proport ion of i n d i v i d u a l s belonging to each stage of growth. Nets of 0*12 mm. mesh were subst i tuted f or those with the OmhO mm. mesh usua l ly used, during three of the times of sampling (19*+9-2123 h r s . , 0305-0^ 02 h r s . , and lVll-1505 h r s . ) . The nets with the larger mesh are considered to have se lected against the smaller growth stages, i . e . , those numbered four and above for Conehoecia elegans and those numbered f i v e or above f or C , pseudohamata. For this reason, concentrations of only the larger stages are considered when comparisons are made. Conehoecia elegans Sars For the most par t th is species ascended a t n ight and descended during the day. Although evidence s trongly suggests that the presence of l i g h t i n i t i a t e s the downward migrat ion , the depth a t ta ined by this migrat ion seems to show l i t t l e r e -l a t i o n s h i p to the depth of penetrat ion of l i g h t . Quar t i l e s f or the n ight d i s t r i b u t i o n had depths ( F i g . 71, dashed l i n e s ) which var ied considerably from month to month. For the f i r s t three months these var ia t ions were r e l a t i v e l y cons i s tent between f i r s t , second, and t h i r d quar t i l e s and between the two s t a t i o n s . In January the three quar t i l e s were r e l a t i v e l y deep a t both s t a t i o n s , i n March they were h i g h , 92 and i n May they were usua l ly low ( F i g . 71). There i s no evidence a t hand that offers an explanation of these v a r i a t i o n s . The depths of quar t i l e s f or the day l i gh t d i s t r i b u t i o n suggest a seasonal trend ( F i g . 71» s o l i d l i n e s ) . They were deeper i n the spr ing and summer months and shallower i n the autumn and w i n t e r . This tendency may have been r e l a t e d to a seasonal increase i n l i g h t penetrat ion . To Investigate th i s p o s s i b i l i t y , the penetrat ion of l i g h t measured wi th in an hour of sampling i s p lo t t ed against the depth of the f i r s t q u a r t l l e of the daytime d i s t r i b u t i o n ( F i g . 77)• The sca t ter of points i n F i g . 77 does not imply any d i r e c t c o r r e l a t i o n between pene-t r a t i o n of l i g h t measured and the depth of d i s t r i b u t i o n for Conehoecia e legans. The fo l lowing evidence suggests that the consistency with which Conehoecia elegans migrates upward during the day decreases with increas ing depth. The f i r s t q u a r t l l e , the one nearest the surface ( F i g . 71) was cons i s t en t ly higher a t n ight than during the day a t both Stat ions 6 and 9 f o r each of the s i x months for which data were examined. The second q u a r t l l e , however, was higher a t n ight i n only f i v e of the s i x months a t the two s t a t i o n s . The t h i r d q u a r t l l e was higher a t n ight four out of s i x times at S t a t i o n 6, but a t only two out of s i x a t S t a t i o n 9« Indiv iduals higher i n the water column appear to have migrated In a more cons is tent manner than those below. In the reg ion of the f i r s t q u a r t l l e they tended always to r i s e a t 9 3 n i g h t and descend during the day, whereas those i n the ne igh-bourhood of the second q u a r t i l e were s l i g h t l y less cons is tent i n the ir movement. The v e r t i c a l movement of the t h i r d q u a r t i l e seems to have expressed a minimum of d i u r n a l contro l* To exp la in these tendencies, the fo l lowing hypothesis i s pos-tulated* Since l i g h t decreases with depth and has a d i u r n a l p e r i o d i c i t y s i m i l a r to that of t h e m i g r a t i o n s , i t seems reasonable to suppose that l i g h t i s the d i r e c t i n g factor* Thus, i n d i v i d u a l s occurr ing high i n the water column a t n ight would descend to avoid the downward penetrat ion of l i g h t during the day; a t n ight they would be free again to migrate i n t o the upper region* Indiv iduals found deep i n the water column would be i n r e l a t i v e darkness* The absence of a stimulus from changing l i g h t would permit more or less u n r e s t r i c t e d freedom of movement* Indiv iduals between the shallow and deep regions would be subject to weak changes of i n t e n s i t y between n ight and day; as a r e s u l t , the i r v e r t i c a l movements would be only p a r t i a l l y c o n t r o l l e d by l i g h t * F i g * 7 3 shows the d i s t r i b u t i o n s of the growth stages of Conchoecia eleeans i n severa l phases of d i u r n a l migration* The r e l a t i v e proportions of the stages do not appear to have d i f f e r e d cons i s t en t ly between the depths* The maximal con-cen tra t ion shows d i u r n a l v e r t i c a l movements i t was deepest i n the afternoon and shallowest i n the la te evening; a t n ight i t s p o s i t i o n was less d i s t i n c t , but i n the morning i t showed d e f i n i t e descent ( F i g . 73)« A secondary peak of concentrat ion was found below the maximum on two occasions (1625-1712 hrs* & 1707-1758 hrs*) near the beginning of the nocturnal ascent . When the maximal concentrat ion was r e l a t i v e l y shallow (19^ 9-2123, 2303-0119, & 0305-0^ 02 h r s , a r e s i d u a l concentrat ion seems to have been present a t depth. Conchoecia pseudohamata n . s p . Indiv iduals of Conchoecia pseudohamata occupying the s h a l -lower depths tended to r i s e a t n ight and descend during the day. In the deeper l e v e l s , however, they appear to have descended a t n ight and r i s e n during the day. In F i g . 72 the depths of f i r s t , second, and t h i r d q u a r t i l e s are p lo t t ed for day l igh t and n ight v e r t i c a l d i s t r i b u t i o n s of Conchoecia pseudohamata. The depths at ta ined by the f i r s t q u a r t i l e a t n ight were not as great as those reached during day l i gh t i n four of the s i x months f or which samples were examined f or both Stat ions 6 and 9* Depths of the second and the t h i r d q u a r t i l e s , on the other hand, were lower a t n ight on f i v e of s i x occasions a t each of the two s t a t i o n s . Whereas the f i r s t q u a r t i l e was u s u a l l y higher a t n i g h t , the second and t h i r d were lower. I t would seem as though the d i r e c t i o n of movement were c o n t r o l l e d by two factors r e l a t e d to depth. In the upper l eve l s . " 95 of the populat ion the presence of l i g h t may have st imulated a downward movement of Conehoecia pseudohamata. Although l i g h t may have ac t iva ted the migrat ion , i t does not seem to have had a d i r e c t bearing on the depth to which migrat ion extended. This lack of c o r r e l a t i o n may be seen by comparing the depths of l i g h t penetrat ion ( F i g . 70) t o t h o s e of the f i r s t q u a r t l l e of the d i s t r i b u t i o n of th i s species ( F i g . 72). As with the other spec ies , the v e r t i c a l d i s t r ibut ions and d i u r n a l v e r t i c a l migrations of the various growth stages of Conehoecia pseudohamata appear to have been not not iceably d i f f e r e n t between the depths sampled (F ig s . 7k to 76). From these d i s t r i b u t i o n s d i u r n a l migrat ion seems to have occurred only i n the shallower depths. General ly the concentrations below 100 m. were greater than those above and d i d not e x h i b i t any d e f i n i t e d i u r n a l v e r t i c a l migrat ion . Above 100 m. , the uppermost occurrence of a concentrat ion sh i f t ed from 90 m. to 30 m. i n the evening, and from 30 m. back to 90 m. i n the morning. Thus, i n the upper 100 m. the species migrated upward a t n ight and downward during the day. TRANSVERSE AND LONGITUDINAL DISTRIBUTIONS D i s t r i b u t i o n s of Conehoecia elegans and £ • pseudohamata are presented on p r o f i l e s of Indian Arm (F igs . 78 to 8l). On these p r o f i l e s , blank areas represent near ly n e g l i g i b l e con-centrat ions ( less than 0.1 i n d i v i d u a l s per **0 l i t r e s of sea water); s t i p p l e d areas ind ica te moderate concentrations (0,1 to 0,9 indiv.AO 1*)} and d i a g o n a l l y - l i n e d areas show high concentrations (greater than 0*9 indiv.AO 1#). A l s o , on each p r o f i l e there i s a dashed polygon represent ing the centre of d i s t r i b u t i o n . This polygon was constructed from pos i t ions and depths determined for the f i r s t and t h i r d q u a r t i l e s of the hor i zonta l . and v e r t i c a l d i s t r i b u t i o n s . The middle 5<$ of the v e r t i c a l d i s t r i b u t i o n i s out l ined approx-imately by the i n t e r q u a r t i l e range between the depths of the f i r s t and t h i r d quar t i l e s a t the s t a t i o n s . The middle 5<$ of the h o r i z o n t a l d i s t r i b u t i o n i s de l imited i n a s i m i l a r manner by the f i r s t and t h i r d quar t i l e s of the d i s t r i b u t i o n as determined by concentrations a t the various s t a t i o n s . The area of i n t e r s e c t i o n of these i n t e r q u a r t i l e distances p r e -sumably indicates the approximate p o s i t i o n occupied by the centre of d i s t r i b u t i o n of the popula t ion . This area i s the dashed polygon on each p r o f i l e , TRANSVERSE DISTRIBUTION Transverse d i s t r i b u t i o n s of the two species are known only . across Stat ions 2, 6, and 12 during day l ight i n J u l y ( F i g s , 78 & 79)» Each d i s t r i b u t i o n was from samples taken a t three pos i t ions across these s t a t i o n s . The order of sampling was f i r s t l y a t the middle, secondly on the west, and t h i r d l y on the eas t . Sampling began a t 0530 hours with S t a t i o n 2 (middle) 97 and ended a t 1230 hours with S t a t i o n 12 (east)* During th i s p e r i o d , the sky was c l ear and the sun, br ight* Unfortunate ly , because time was l i m i t e d , l i g h t measurements were not taken* Since sampling at S t a t i o n 2 succeeded sunrise by only a few hours, the angle of incidence of the sun l igh t and the height of the i n l e t w a l l probably allowed br igh t l i g h t to be cast a t f i r s t only on the western s ide* . When S t a t i o n 6 and 12 were being sampled, on the other hand, the rays of sun l ight were a t a l e s ser angle of incidence and probably l i gh ted the i n l e t across i t s ent ire width . The d i s t r i b u t i o n s , e s p e c i a l l y those across S t a t i o n 2, Indicate that l i g h t may be an Important fac tor i n the I n i t i a t i o n of the downward migrat ion of both species* Conehoecia elegans Sars Across S t a t i o n 2, the areas of moderate and high concentra-t i o n were deeper i n the west than i n the east and deepest i n the middle j si lso, the centre of d i s t r i b u t i o n was d isp laced toward the east (Fig* 78)* Across S t a t i o n 6, the area of moderate concentrat ion was shallower on the sides than i n the middle , while the area of higher concentrat ion was at: the,,same l e v e l across the ent i re width of the inlet} the centre of d i s -t r i b u t i o n was near ly centra l* Across S t a t i o n 12, the area of moderate concentrat ion was a t the same l e v e l across the three pos i t ions of sampling, and the centre of d i s t r i b u t i o n was 98 central. An area of high concentration was absent at Station 12, probably because of a slight up-inlet displacement of the population shown, for July (see below, Longitudinal Dis-tribution), The deepest level of moderate concentration at Station 2 was shallower than the shallowest levels at Stations 6 and 12, If the difference i n depth between the eastern and western sides at Station 2 had been due to a time-controlled diurnal v e r t i c a l migration, the organisms present at the f i r s t position occupied would have been sampled earlier in their daytime des-cent and would have been found at a shallower l e v e l . Organisms sampled earlier (those on the east), however, were found at a deeper level than those sampled later (on the west at Station 2 and at a l l positions across Stations 6 and 12), It is possible that the distribution outlined above provides a demonstration of the effect of li g h t on the v e r t i c a l distribution of the population. In the early morning, when positions across Station 2 were being sampled, the sun was low In the east, shining f i r s t upon the west side of the in l e t while the east side was shaded by the high i n l e t wall. The distribution on the lighted side of Station 2 (west) approached the greater depths obtained at Stations 6 and 12, It seems probable, therefore, that the attainment of a certain amount of ligh t was responsible for the downward migration of the species. The distributions of moderate and high concentrations at Station 2 and of moderate concentration at Station 6 are _. . . . . 99 characterized by being depressed i n the mid-inlet positions (Fig. 78). This suggests that individuals inhabiting the middle part of the inl e t may have migrated more or less directly downward whereas those found at the sides may have had to migrate diagonally toward the midline of the inl e t i n order to reach the same depth as those in the middle. Individuals at the sides, therefore, would have taken longer to descend than those i n the middle. &t Station 12, however, the distribution was not lower i n the middle than on the sidesj i t was level across the in l e t and at the same depth as on the sides at Station 6, The distribution at Station 12 does not seem to have completed i t s retreat from the shallow water, perhaps because of the restricted depth in this part of the in l e t . Conehoecia pseudohamata n.sp. The transverse profiles for the distribution of Conehoecia  pseudohamata (Fie. 79") show similarities to those for C. elegans. On the western side and middle of Station 2, and at a l l positions at Stations 6 and 12, the levels of moderate concentration were at about the same depth, whereas on the eastern side at Station 2, the level was shallower. High concentration (^ 0.9 indiV^OL) occurred only below 100 m. and, therefore, only at Station 6. The centre of distribution was central at Stations 6 and 12, but was t i l t e d upward toward the 100 east a t S t a t i o n 2. The shallowness of the d i s t r i b u t i o n on the eastern s ide of S t a t i o n 2 may have been r e l a t e d to the shading of th i s s ide of the i n l e t from the l i g h t of the r i s i n g sun. Probably, on th i s occasion, l i g h t on this s ide was not intense enough to penetrate to the organisms and st imulate the ir downward migra t ion . The areas of concentrat ion Lack the depression a t the m i d - l i n e of the i n l e t such as was found f o r Conchoecia e l e - gans. This even d i s t r i b u t i o n may indicate that C , pseudoham- ata d i d not migrate d iagona l ly , but moved more or less d i r e c t -l y downward to a depth that could be accommodated a t the s ide p o s i t i o n s , LONGITUDINAL DISTRIBUTION The areas of moderate and high concentrat ion and the centre of d i s t r i b u t i o n of each species are shown on l o n g i t -u d i n a l p r o f i l e s of Indian Arm (Figs , 80 & 81), To r e v e a l the poss ib le e f fects of oceanographic fac tors i n the absence of l i g h t , these p r o f i l e s were constructed from data c o l l e c t e d a t n i g h t . Such p r o f i l e s are presented for the months of January, March, May, J u l y , September, and November, Average concentrations a t the various s tat ions are shown f o r each species (F igs , 82 to 85) f or each of the s i x months mentioned above. These concentrations have been d iv ided to show the r e l a t i v e proportions contributed by the various 101 growth stages* Data front both n ight and day c o l l e c t i o n s are presented* The degree of confinement of each species to the i n l e t i s expressed by the frequency of i t s occurrence a t Stat ions 15 and 23 (F ig s . 86 & 87). Conehoecia elegans Sars Examination of F i g * 80 shows that the edge of the area of moderate concentrat ion ( s t ippled) of Conehoecia elegans often approached the surface , but d i d not reach i t * Even though specimens were found frequent ly a t 30 m. , only two were obtained from about 70 samples c o l l e c t e d a t the surface* For some reason Conehoecia elegans f a i l e d to inhab i t the surface water* Perhaps the thermocline or the ha loc l ine acted as a b a r r i e r preventing the organism from ascending in to the water near the surface* According to the pos i t ions of the centre of d i s t r i b u t i o n and the main area of h igh concentrat ion (Fig* 80), the populat ion of Conehoecia elegans moved down-inlet i n January and March to u p - i n l e t i n May; and from s l i g h t l y u p - i n l e t i n September to down-inlet i n November* The u p - i n l e t movement from March to May was more or less co inc ident with condit ions brought about by the entry of f o r e i g n water to the i n l e t during the e a r l y p a r t of the year* During the per iod from March to May, the 102 d i s t r i b u t i o n of temperature ( F i g , 63) showed a progressive u p - i n l e t mixing of the colder f o r e i g n water with warmer r e s i -dent water. I t was during th i s per iod that the centre of d i s t r i b u t i o n and the area of high concentrat ion sh i f t ed from the colder to the warmer water. The temperature d i s t r i b u t i o n indicates that i n J u l y , September, and November, u p - i n l e t mixing was more or less completed and oceanographic condit ions were s t a b l e . During J u l y and September the d i s t r i b u t i o n was only s l i g h t l y down-i n l e t from the p o s i t i o n occupied i n May. In November, however, i t was found to have sh i f t ed decidedly down-inlet . At th is time the d i s t r i b u t i o n s of temperature and s a l i n i t y showed no not iceable change which could be used to exp la in th is movement. The d i s t r i b u t i o n s of the various growth stages are shown i n F i g s . 82 and 83 where the average concentrat ion i n the water column a t each s t a t i o n i s d iv ided to show the r e l a t i v e pro -port ions of f i r s t (adult /> and £ ) , second (2), and smaller (>2) s tages. The re su l t s of n ight sampling are presented i n F i g . 82, and those of day l i gh t sampling, i n F i g . 83. Unless l a t e r a l or l o n g i t u d i n a l movement were s i g n i f i c a n t over a d i u r n a l p e r i o d , or sampling v a r i a t i o n were l a r g e , the curves obtained by day and by n ight sampling should be s i m i l a r . Average concentrations were higher at S t a t i o n 9 i n January and March, a t S tat ions 2 and 6 i n May, a t S t a t i o n 6 i n J u l y 103 and September, and at Station 12 in November (Figs. 82 & 83). These shifts i n position of greater abundance are similar to those shown by the dashed polygon in Fig. 80 for the centre of distribution of the population. In January, March, and November, the higher average concentrations^occurred nearer the mouth (near Stations 9 and 12); these appear to have been composed of a relatively larger number of younger stages (Figs. 82 & 83). Perhaps the water in the v i c i n i t y of Stations 9 and 12 was the medium i n which many younger states had hatched or to which many of them had been attracted. Except in May the concentrations and relative proportions at the various stations were similar during night (Fig. 82) and day (Fig. 83), At night i n May, the highest concentration occurred at Station 2, whereas during daylight i t was present at Station 6. Perhaps during daylight the large number of individuals present could not be accommodated by the limited depth at Station 2. During the day, therefore, a proportion of individuals may have been forced to move down-inlet toward Station 6 i n order that some depth demanded by their diurnal migration might be reached. The concentrations of Conchoecia eleeans at Stations 15 and 23 are plotted against depth for each month when samples were available.(Fig. 86). Samples collected from Stations 15 and 23 i n March, A p r i l , May, June, July, September, and from Station 15 in January, indicate concentrations less than 0.06 indlvidualsAO l i t r e s for Station 15 and less than 0.02 i n d i v . A o 1. for Station 23. Collections in February and November, on the other hand, indicate concentrations greater than 0.8 i n d i v . A o 1, at Station 15 and greater than 0,5 i n d i v . A o !• at Station 23. Although concentrations were higher in February and November, they were low compared to the 0.1 to 0.9 i n d i v . A o 1. found at similar depths at the other stations. In November, when concentrations oyer the s i l l were higher, the centre of the population was found to be close to the mouth of the inlet (Fig, 80, dashed polygon^. The . population may well have had a similar position in February when the concentration was likewise higher. This position i s suggested by the distribution for January and March (Fig. 80) when the centre of the population was not far from the mouth. If this occurrence near the mouth had been coin-cident with the increase in average concentration that took place i n the whole of Indian Arm between January and March (Fig. 88), then recruitment of organisms from outside would be suspected. Increase in the proportion of young from January to March, however, indicates that the increase in average concentration was due to reproduction, probably within the i n l e t . (Compare the proportion of adults to individuals of a l l stages, Fig. 88.) In November, samples were taken during both ri s i n g and f a l l i n g tides (Fig. 86, Nov., f & e). On the ris i n g tide, . 105 samples from Stations 15 and 23 gave average concentrations of 0,05 indiv.AO 1. and.0.03. indiv.AO 1., respectively, whereas on the f a l l i n g tide, average concentrations were 0.07 indiv.AO 1. and 0.0*+ indiv.AO 1. If these values were to di f f e r significantly, they would suggest that some individuals were being transported out of the i n l e t . It is possible that ostracods could have been recruited during a r i s i n g tide. During the month of March, for instance, a large rise i n tide was shown to have injected a tongue of water into the inl e t (see above, Tide). Samples indicate, however, that very few individuals were present at Station 15 during this period (Fig. 86). It must be admitted that the data are inadequate for proving that Conchoecia eleeans was not introduced into the i n l e t . The species may have been introduced in February. The evidence suggests, however, that a good proportion of the increase i n population that occurred during this period was due to the production of young within the Inlet. Conchoecia pseudohamata n.sp. Generally, moderate concentrations of Conchoecia pseudo- hamata (Fig. 81, stippled) occupied intermediate depths, but they were found also i n patches^during March at lesser depths, and during November at greater depths. High concentrations (diagonally lined) were usually deep but existed also as patches i n shallower regions during July and September, As the year progressed, higher concentrations occupied greater proportions of the p r o f i l e s and came closer to the surface. Although specimens occurred quite frequently i n samples from 3 0 in., they were present i n only two of about 70 surface samples examined. Perhaps the sharp gradients of temperature and s a l i n i t y c h a r a c t e r i s t i c of the waters between 0 and 3 0 m. caused this absence. The centre of d i s t r i b u t i o n of the population usually remained i n the up- i n l e t portion of the deep basin. In May, July, and November, however, i t spread down-inlet. I t usually occurred between 90 m. and the bottom, although i n September i t seems to have been at a s l i g h t l y shallower depth. As the year progressed, the areas of high concentration were found to extend v e r t i c a l l y and l o n g i t u d i n a l l y . This extension may have been due l a r g e l y to the general increase i n the population shown i n F i g . 88. In January, March, and May (Fig* 81) the area of high concentration was prominent up - i n l e t and seems to have proceeded s l i g h t l y toward the head during t h i s period. In July, this concentration was more or less evenly d i s t r i b u t e d along the basin; i n September and November, i t was s l i g h t l y down-inlet. The population of Conehoecia elegans had a s i m i l a r , but more extensive movement than the one shown here f o r C. pseudo-107 hamata. Perhaps the tendency of C. pseudohamata to Inhabit deeper water caused it s movement to be restricted to the deep basin of the i n l e t . The distributions of the various growth stages are shown for the six months for which collections were examined. In Figs, 8 -^ and 85 the average concentration in the water column at each station is plotted and divided to show the relative proportions of f i r s t G# and ?), second ( 2 ) , third ( 3 ) , and smaller (>3) stages. The results of night sampling are presented in Fig, 8*+, and those of daylight sampling, i n Fig, 8 5 . Except"in March and July the proportions of the various growth stages were similar between station positions. In March, the daylight distribution (Fig, 8 5 ) indicates that a higher proportion of younger stages (>3) occurred at Station 6 than at Station 9 j the night distribution (Fig. 8*+), on the other hand, shows that the stages have similar proportions at these two stations. The night distribution i n July shows a higher proportion of younger stages (>3) at Station 9 than at 6 , but the daylight distribution indicates that the relative proportions of the growth stages were similar for the two stations. The above evidence suggests that concentrations of the small stages (>3) were present occasionally in patches. Per-haps breeding occurred i n swarms and the resultant young, 108 therefore, also occurred in swarms. Before becoming dispersed, these young organisms may have been in large numbers when particular stations were being sampled* On the whole, the relative proportions of the growth stages were similar from month to month* In January and March, however, the smaller stages (>3) seem to have been sli g h t l y more numerous than during other months* This increase may have been related to breeding during or prior to this period* The concentrations of Conchoecia pseudohamata at Stations 15 and 23 are plotted against depth for each month during which samples were available* (Fig* 87)* Individuals of the species occurred only rarely at these stations, and then i n very small numbers* Collections which contained specimens were taken only at night* Specimens were collected from Station 15 during f a l l i n g tides in February and May and from Station 23 during a rising tide i n June} they were absent from samples taken i n other months and from those taken during a r i s i n g tide i n May* The absence of specimens from daylight collections at Stations 15 and 23 agrees with the observation that the species did not occur i n shallow waters during the day* The general scarcity i n the region of the s i l l indicates that there was l i t t l e exchange of individuals between Indian Arm and outside water. If the exchange indicated by the more frequent occur-rences of specimens duringfalling tides were significant, i t 109 would suggest that individuals were lost from Indian Arm rather than recruited from outside. From the present evidence, i t seems that the population of Conchoecia pseudohamata was self-sustaining and independent of replenishment from outside water and, as well, was probably largely confined to the basin of Indian Arm. SEASONAL VARIATION IN FECUNDITY Most of the growth stages of Conchoecia eleeans and C. pseudohamata were present throughout the year (Figs. 82 to 85)} the adult females were rarely without eggs. These facts suggest that some breeding took place at a l l times. Probably breeding was maximal when the proportion of females with most of their eggs mature was highest. Any increase in the proportion of young would indicate that breeding had been high at some prior period. Conchoecia eleeans Sars As shown in Fig. 89,the proportion of adults to individuals i n a l l growth stages of Conchoecia eleeans captured was relatively low in January and March, higher i n May and July, highest in September, and low again in November. It follows that the proportion of individuals in the younger stages was 110 r e l a t i v e l y high i n November, January, and March. During these three months, the higher proportion of these younger individuals occurred i n the v i c i n i t y of Stations 9 and 12 (Figs. 82 & 83). In May and July about 90$ of the adult females had most of th e i r eggs mature. At other times this proportion ranged between 10 and 60$. Thus, nearly a l l of the adult females had most of their eggs mature during the summer. The above evidence suggests that breeding occurred i n the early summer months, when the adults seem to have been sexually mature. The increased number of individuals occurring i n the younger stages from autumn to spring suggests that many of the young, hatched a f t e r the summer breeding, had grown to a s i z e large enough to be captured by the plankton samplers• Conehoecia pseudohamata n. sp. As shown i n F i g . 90, the proportion of adults to i n -dividuals i n a l l growth stages caught decreased from January to March, remained low during May, and increased from May to November. I t follows that the proportion of younger individuals increased from January to March and perhaps also during a period j u s t p r i o r to t h i s . The proportion of females with most eggs mature was low Q+0 to 60$) i n November and January, and high (80 to 90$) I l l • during the other months. This suggests that the females were In condition for breeding from early spring to early autumn, FOODS of Conchoecia eleeans Sars and Conchoecia  pseudohamata n. sp. Stomachs of adult specimens of Conchoecia eleeans and C. pseudohamata taken from 60and.90. m* depths during September were examined and found to contain both plant and animal material. Plant material consisted of whole skeletons of s i l i c of lage Hates, armoured dinof la ge Hates, and whole and fragmented frustules of centric diatoms. Animal material consisted of fragments of crustaceans. There were also particles which appeared to have been d e t r i t a l , but may have been the partly digested soft parts of the plants and animals ingested. Individuals varied in the amount of food and the re-lative proportions of plant and animal material contained within their stomachsj some stomachs appeared to be empty. The diameters of whole centric diatoms and the widths of fragments of crustacean parts measured up to 65 microns, implying that the species were capable of consuming relatively large particles. 112, DISCUSSION The present study has aimed at exploring the general distributional and ecological relationships of the plank-tonic ostracods of Indian Arm. Most conclusions therefore have been of a general nature also. Numerous points of interest have had to be l e f t for later study to maintain this approach; most of these points w i l l require individual attention with the use of refined methods for the purpose of acquiring detailed information. Light has a diurnal periodicity and often i t s effects cannot be distinguished from other effects related to the time of day. In the present study there was an occasion when light and time of day were not coincident. Due to the angle of sun-ligh t in the early morning and the height of the inlet wall, light f e l l on the west side of the inlet while the east side remained in shadow. Probably this was the reason that both Conehoecia elegans and G, pseudohamata showed a deeper dis-tribution on the west than on the east. This evidence suggests that light could be a factor influencing the daylight descent of these ostracods. Davidson (192*0 suggested that light influenced the depth of distribution of Conehoecia elegans i n the region of the Gulf of St. Lawrence. She found that the populations were deeper in oceanic waters than In coastal waters and attributed 1 1 3 this difference to the smaller amount of l i g h t penetrating through the more turbid water nearer the coast. This seems to be another instance i n which l i g h t differences, independent of the time f a c t o r , appear to e x h i b i t some influence on the depth of d i s t r i b u t i o n . Neither species i n Indian Arm showed a good c o r r e l a t i o n between the depth of i t s d i u r n a l descent and the depth of penetration of l i g h t . Perhaps the organisms within the influence of l i g h t were stimulated to descend or ascend by the presence or absence, respectively, of a c e r t a i n minimum amount of l i g h t . This hypothesis does not require that l i g h t maintain control while the organism i s migrating. Possibly a c e r t a i n optimum i n t e n s i t y of l i g h t did control the depth achieved during the migration but the i n t e n s i t y measured was not that of the s p e c i f i c wave-length e f f e c t i v e i n this c o n t r o l . Future work on this problem would require that l i g h t i n the environment be measured by a photometer capable of d i s t i n g u i s h i n g between various wave-lengths, and that r e l a t i o n s h i p s between l i g h t and the migration of these organisms be investigated i n the laboratory. Diurnal migration d i f f e r e d f o r the two species. The d i s -t r i b u t i o n of Conehoecia elegans was usually higher at night than during the day i n the region of the f i r s t and second (shallower) q u a r t i l e s , while i t was neither consistently higher nor lower i n the region of the t h i r d (deeper) q u a r t l l e . . ....... • I l k In C. pseudohamata. only the f i r s t , q u a r t i l e was higher night than during the day; the second and t h i r d quartiles were usually lower at night. The l a t t e r evidence indicates that the upper two-thirds of the population of Conchoecia eleeans and the upper one-t h i r d of that of C. pseudohamata were higher i n the water column a t night than during the day. Observations made i n July (Figs, 7^  to 76) suggest that the upward migration of C, pseudohamata was d e f i n i t e l y i n the upper 100 mj below this depth d i s t i n c t migration was not detected. Near absence from the surface water was a consistent feature of the d i s t r i b u t i o n s of both species. At night, when the organisms were highest i n the upper part of the water column, specimens were frequently taken from 30 m., but only r a r e l y from the surface water. Within the upper 5 to 10 m. there were steep gradients within the thermoclineand halocline which may have prevented the ostracods from reaching the surface water. Unfortunately, since no samples were taken between 0 and 30 m., this feature could not be checked. I f th i s problem were pursued fa r t h e r , a large number of samples would have to be c o l l e c t e d to compensate f o r the low pro-b a b i l i t y of obtaining a representative sample from the small number of organisms present i n this zone near the surface, Stephensen (19^ 3) l i s t s only one instance where Conchoecia  eleeans from the eastern coast of Greenland was shown to occur near the surface (0 - 5m.), Since this l i s t omits mention of hauls not containing the species, the significance of this single occurrence cannot he estimated. Davidson (192*0, working on material from the Gulf of St. Lawrence, found C. elegans to occur occasionally at the surface oyer the continental shelf and suggested that such occurrences were related to night rising and to upwelling. In the region of the Laurentian Channel, on the other hand, the species was less abundant and rarely occurred at the surface. A salinity gradient in the surface water of the Laurentian Channel may have been steep enough to prevent the species from moving upward as i t was observed to do over the shelf. In Indian Arm the two species_were most abundant in a temperature range of 7 to 9° C • and a salinity range of 26 to 27°/oo. Jesperson (1923) recorded Conehoecia elegans as having been collected from water of a negative temperature and from water of salinity greater than 3*f°/oo. Elofson (19^ 1) reported that the species had been found in water of tem-peratures between -l.U-9 and +23.5°C» and of salinites from 19*96 °/oo to over 35 °/oo. He concluded that the species was eurythermal and euryhallne. The present study does not contradict this conclusion although i t does show that tem-perature, salinity, or some other factor may influence the distribution, at least temporarily. Conehoecia pseudohamata was collected at the Ocean Weather Station «*Pn (50° 00* N., 1^ 5° 00* W.) by a vertical net haul 116 from 1,250 m. to the surface (personal communication from F. Neave and R. J . Le Brasseur, B i o l o g i c a l S t ation, Fisheries Research Board of Canada, Nanaimo, B. C. This column of water had temperatures between 2.6 and 12.2° C. and s a l i n i t i e s between 32*7 and 3^ .5 °/oo (Tabata, M c A l l i s t e r , Robertson, and H o l l i s t e r , I960), Because the actual depth at which the specimens were c o l l e c t e d i s unknown, the temperature and s a l i n i t y at which they occurred i s also unknown. In Indian Arm the population of Conchoecia eleeans seems to have moved from down-inlet to up-inlet during the f i r s t h a l f of the year and from u p - i n l e t to down-inlet during the l a t t e r h a l f of the year (September to November). The population of C. pseudohamata showed a s i m i l a r movement, but one which was much more conservative than that of the other species. The occurrence of an i n t r u s i o n of low-temperature, high-s a l i n i t y , highly oxygenated water in t o Indian Arm during the e a r l i e r portion of the year may have contributed to the up-i n l e t movements of these populations. No such oceanographic change was noticeable, however, during t h e i r down-inlet movements. The oceanographic and b i o l o g i c a l changes that occurred e a r l i e r could not be exactly r e l a t e d . I t i s believed that any r e l a t i o n s h i p would have been quite complicated. Perhaps some unmeasured oceanographic f a c t o r , entering l a t e during the period of i n t r u s i o n , was e f f e c t i v e i n r e p e l l i n g the species from the down-inlet region of the i n l e t . Carrying 117 this hypothesis farther, the unknown factor might be suggested to have maintained i t s re p e l l e n t e f f e c t u n t i l such time ( l a t t e r h a l f of the year) as i t became s u f f i c i e n t l y d i l u t e d by mixing with water of other sources present i n the i n l e t . Further pursuit of this problem would require some laboratory experimentation to determine the tolerances of the organisms to various combinations of temperature, s a l i n i t y , oxygen content, and other factors that might influence t h e i r d i s t r i b u t i o n s . Conehoecia elegans was found i n the water over the s i l l of Indian Arm more often than was C, pseudohamata. This d i s s i m i l -a r i t y was probably related to the d i f f e r e n t heights of d i s -t r i b u t i o n of the two species and to the shallow s i l l depth (about 30 m.). The r e l a t i v e heights of d i s t r i b u t i o n may be i l l u s t r a t e d by comparing depths of the f i r s t q u a r t l l e of the v e r t i c a l d i s t r i b u t i o n of each species. For ( J . pseudohamata. the f i r s t q u a r t l l e was always deeper than 75 m« (Fig. 71) whereas f o r C. elegans i t was often shallower than this depth (Fig . 72) . Also, the area of moderate concentration (0.1 to 0.9 individuals/hO l i t r e s ) was shallow i n the down-inlet region more often f o r C. elegans (Fig. 80) than f o r C. pseudo- hamata ( F i g . 81) . Individuals of C. elegans. therefore, would be more l i k e l y than those of C. pseudohamata to become en-trained i n outflowing water within the upper 30 m. (the depth of water over the s i l l ) . Although the present study indicates that recruitment of 118 the ostracods from outside the I n l e t was not extensive, the evidence i s not conclusive. To investigate properly the exchange of organisms between Indian Arm and outside waters, water entering and leaving would have to be sampled continually, an Impracticable task at present* Perhaps the economy of sampling could be improved by s e l e c t i n g the time f o r sampling on the basis of periodic checks on the conditions within the i n l e t and around the area of the mouth* An extensive study on growth, reproduction, and longevity would be required as a basis f o r explaining increases or decreases within the i n l e t * The evidence at hand suggests that the time of maximal breeding i n Indian Arm occurred during the early summer months f o r Conchoecia eleeans and from early spring to early autumn f o r C. pseudohamata* Klelhorn (1952) estimated the breeding season of C, elegans i n the Labrador Sea to be from August through November; he found numerous young from August through January* Wiborg (195^), i n his i n v e s t i g a t i o n of three species of Conchoecia. namely, C. elegans Sars, C. borealis Sars, and C. obtusata Sars, from off the coast of Norway, found that the stock increased from October-November to a maximum i n January-February and estimated this period to be the time of main propagation* He found small individuals to be abundant from November to May* The breeding season of C. elegans appears to have been s l i g h t l y d i f f e r e n t f o r the three regions -Indian Arm, the Labrador Sea, and the coast of Norway. 119 Examination of stomach contents of specimens taken from Indian Arm during September revealed that both Conehoecia  elegans and C. pseudohamata were omnivorous organisms capable of devouring r e l a t i v e l y large p a r t i c l e s (eg. 65 microns). Elofson (19^ 1) reported that C. elegans as w e l l as C. borealis and C. obtusata from off the Swedish coast contained b r i s t l e s and s k e l e t a l parts of copepods i n their stomachs. He remarked that they were carnivorous. Tchindonova (1959) reported the foods of three species of Conehoecia from the northwestern P a c i f i e s Conehoecia al a t a contained the remains of Crustacea, d e t r i t u s , phytoplankton, t i n t i n n i d s , r a d i o l a r i a , medusae, and globigerins; C. ametia 1 contained a l l the l a t t e r foods 2 except the phytoplankton and medusae; and Conehoecia n.sp. possessed only d e t r i t u s . Ostracods of the genus Conehoecia seem to be capable of eating a wide v a r i e t y of small organisms and p a r t i c l e s . The species from Indian Arm did not d i f f e r i n this respect, the remains of Crustacea, s i l i c o f l a ge H a t e s , dinof l a ge H a t e s , and diatoms being found i n their stomachs. 1 Conehoecia ametia i s unknown to the author; perhaps i t i s a misspelling of C. ametra Muller. 2 Neither s p e c i f i c t r i v i a l name nor d e s c r i p t i o n mentioned. 120 SUMMARY 1. Of the four species of ostracods found i n the plankton of Indian Arm, Paradoxostoma striuneulum Smith and Philomedes sp. are not considered normally planktonic whereas Conchoecia  eleeans Sars and C. pseudohamata n.sp. are abundant members of the plankton. 2. Variations from previous descriptions of Paradoxostoma  striuneulum Smith and Conchoecia elegans Sars are considered i n s u f f i c i e n t f o r separation of the described forms from those i n Indian Arm. 3. Conchoecia pseudohamata i s proposed as a new species. ti I t i s included i n Muller *s subgeneric c l a s s i f i c a t i o n , the a lata-group; i t s closest r e l a t i v e i s regarded as C. a l a t a it Muller. k. Philomedes sp. may be a new species. Since only one specimen was a v a i l a b l e , however, this could not be established. This form i s c l o s e l y related to Philomedes carcharodonta Smith. 5. Specimens of Conchoecia elegans and C. pseudohamata obtained from other i n l e t s of B r i t i s h Columbia were sim i l a r i n diagnostic features and s h e l l measurements to those found i n Indian Arm. Specimens of C. pseudohamata co l l e c t e d from the Ocean Weather S t a t i o n "Ptt (50° 00' N., lh5° 00» W.) had 121 diagnostic features which were similar to those from Indian Arm, but had shell measurements which were about one-third larger. 6. Both Conehoecia elegans and £. pseudohamata were nearly absent from the near surface water. This absence may be attributed to adverse effects of steep gradients of temperature and sal i n i t y found in the thermocline and haloclihe. 7 . An examination of the distributions of certain ocean-ographic factors — temperature, sa l i n i t y , and dissolved oxygen — revealed that a large quantity of water originating from outside the inlet had entered the deeper strata of Indian Arm during the early months of the year. 8. Up-inlet movements of the populations of Conehoecia  elegans and £. pseudohamata during the early months of the year may have been related to the intrusion (see item 7 above). Down-inlet movement of these populations, on the other hand, could be related to no such oceanographic change. 9. Both Conehoecia elegans and pseudohamata existed within the relatively limited ranges of temperature and sa l i n i t y found below the thermocline and halocline in Indian Arm ( 7 to 9 ° C. and 2 6 to 2 7 °/oo). Published information, however, indicates that both species may inhabit other waters having more extreme temperatures and s a l i n i t i e s . 122 10. The distribution of oceanographic factors suggested that t i d a l currents may have been a mechanism by which water and perhaps biota could have been transported to and from the i n l e t . 11. The populations of both species were more or less res-tricted to Indian Arm, probably because of the shallowness of the s i l l . Conchoecia elegans Sars seems to have been less confined probably because i t occurred more frequently in shal-low depths than did the other species, 12. Diurnal ve r t i c a l migration differed between the two species. Individuals of Conchoecia elegans at upper and inter-mediate depths migrated upward at night and downward during the day, whereas those at greater depths showed no definite diurnal migration. Individuals of £. pseudohamata in the upper part of the water column tended to migrate upward at night whereas those in the intermediate and lower depths Indicated a downward migration at this time. 13. The influence of light on the ve r t i c a l distribution of individuals in the shallower depths was indicated on an occasion in the early morning when one side of the inlet was i n light before the other. Both species occurred at shallower depths on the side that was shaded and at greater depths on the side that was f i r s t lighted. lk. The times of maximal breeding seem to have been 123 similar for both species* For Conehoecia elegans maximal breeding was estimated to have occurred in the early summer months; for C, pseudohamata i t may have taken place from early spring to early autumn. 15. Examination of stomach contents revealed that Conehoecia elegans and C. pseudohamata are omnivorous organisms capable of devouring relatively large particles. R E F E R E N C E S 12k Anon., 1961. Indian Arm c r u i s e s . Univ. B. C.« Inst. Ocean- oer.. Data Rep. 18s 1-6V (mimeog.). Baird, W., 1850. The natural history" of the B r i t i s h Entomos-traca, Ray S o c , London, 36*+ pp. Barnes, H., 19^9• On the volume measurement of water f i l t e r e d by a plankton pump, with an observation on the d i s t r i -bution of plankton animals. J . Mar. B i o l . Ass. U.3C.. 28$ 651-62. Barnes, H. and Marshall, S.M., 1951. On the v a r i a b i l i t y of r e p l i c a t e plankton samples and some applications of Contagious 1 1 series to the s t a t i s t i c a l d i s t r i b u t i o n of catches over r e s t r i c t e d periods. J . Mar. B i o l . Ass. U. K.y 30J 233-63. Barney, R. W., 1921. Ostracoda. Nat. H i s t . Rep. Terra Nova Exped., 3s 175-90. Benson, R. H., 1959* Ecology of Recent ostracodes of the Todos Santos Bay Region, Baja C a l i f o r n i a , Mexico. Paleont. Contr. Univ. Kans.. 23s 1-80. Brady, G. S., 1907. Ostracoda. Nat. Antarct. Exped. 1901-190*+« Nat. H i s t . . 3(5)s 1-9. Cameron, F. E., 1957* Some factors influencing the d i s t r i b u t i o n of pelagic copepods i n the Queen Charlotte Islands area. J . F i s h . Res. Bd. Can., iki 165-202 Campbell, M. H., 1929. A preliminary quantitative study of the zooplankton i n the S t r a i t of Georgia. Trans. Roy. Soc. Can., ser. 3, 23s 1-28. Cannon, H. G . , 19*+0. Ostracoda. S c i . Rep. Murray Exped.. 6s 319-25. Clarke, G. L. and Bumpus, D. F., 1950. The plankton sampler — an instrument f o r quantitative plankton investigations. Amer. Soc. Limnol. and Oceanogr.. Sp. Publ. 5» 8 pp., revised from 19^0 e d i t i o n . Claus, C , 1891. Die Halocypriden des Atlantlschen Oceans und Mittelmeeres. K. Akad. Wiss. Wien, Wien, 81 pp. Dana, J . D., 18^9. Conspectus crustaceorum quae i n orbis ter-rarum circumnavigatione, Carolo Wilkes e classe repub-l l c a e federatae duce, l e x i t et d e s c r i p s t i Jacobus D. Dana, pars I I . Proc. Amer. Acad. ArtsGSci.. 2s9 - 6 l Davidson, V. M., 192*f. The d i s t r i b u t i o n of c e r t a i n marine Ostra-coda i n Canadian waters of the eastern coast. Contr. Canad. B i o l . , n.s., 2s 297-306. . 125 Elofson, 0., 19^ 1. Zur Xenntnis der marinen Ostracoden Sch-wedens mlt besonderer Berucksichtigung des Skageraks. Zool. Bi d r . Uppsala. 19: 215-53*+ Fowler, G. H., 1909. The Ostracoda. Biscayan plankton c o l l e c t e d during a cruise of H.M.S. Research, 1900. Trans.Linn. Soc. Lond. (Zool.). ser, 2, 10$ 219-336. Freund, J . E. 1952* Modern elementary s t a t i s t i c s . P r e ntice-Hall, Englewood C l i f f s , hlQ pp. Gilmartin, M. i960. The primary production of a B r i t i s h Columbia f j o r d . Unpublished Ph.D. thesis, Univ. B, C , 196 leaves. Granata, L. and Caporiacco, L, d l , 19*+? • Ostracodes marins r e c u e i l l l s pendant les c r o i s i e f e s du Prince Albert l e r . Result. Camp. S c i . . Monaco. 109. 1-51. l i e s , E. J . , 1953. A preliminary report on the Ostracoda of the Benguela Current. 'Discovery 1 Rep.. 26: 259-80. Jesperson, P. 1923. Dr. T h o r i l d Wulff*s plankton-collections i n the waters west of Greenland: Metazoa. MeddT Grinland. 103-60. Johnson, M. W., 1932. Seasonal d i s t r i b u t i o n of plankton at F r i -day Harbor, Washington. Univ. Wash. Publ. Oceanoer.. 1: I-38. Juday, C., 1906. Ostracoda of the San Diego Region, I., Univ. C a l i f . Publ. Zool.. 3: 13-38, Juday, C , 1907. Ostracoda of the San Diego Region, I I . Univ. C a l i f . Publ. Zool.. 3: 135-56. Kesling, R. V., 1951. The morphology of Ostracoda molt stages. I l l i n o i s B i o l . Monoer.. 21 (1-3): 1-32^ . Kielhorn, W. V., 1952. The biology of the surface zone zooplank-ton of a boreo-arctic A t l a n t i c Ocean area. J . F i s h . Res. Bd. Can.. 9: 223-6V, Kornicker, L. S., 1958. Ecology and taxonomy of Recent marine ostracods i n the Bimini area, Great Bahama Bank. Univ. Tex.. Inst. Mar. S c i . . Publ. 5: 19^ 300. Lea, H., 1955* Chaetognatha of western Canadian coastal waters. J . F i s h . Res. Bd. Can.. 12: 593-617. Le Brasseur, R. J . , 195^ . The ph y s i c a l oceanographic factors governing the d i s t r i b u t i o n "of plankton i n the B r i t i s h Columbia i n l e t s . Unpublished M.A. thesis, Univ.B.C., 52 leaves. 126 Legare, J . E. H., 1957. The q u a l i t a t i v e and quantitative d i s -t r i b u t i o n of plankton i n the S t r a i t of Georgia i n r e l a t i o n to c e r t a i n oceanographic f a c t o r s . J . Fish.Res. Bd. Can.. Iht 521-52. Levinson, S. A., 1957. Bibliography and index to new genera and species of Ostracoda for 1956. Micropaleontoloey. 3 5 367-92. Lucas, V. Z., 1931. Some Ostracoda of the Vancouver Island Region. Contr. Canad. B i o l . , n.s., 6s 399-^16. McHardy, R.A., 1961. C a l i b r a t i o n of Clarke-Bumpus plankton sam-plers i n the f i e l d . Univ. B. C . Inst. Oceanoer.. MS  Rep. 8s 1-10 (mimeog.). 11 n Muller, G. W., I 8 9 3 . Uber Lebensweise und Entwicklungsgeschichte der Ostracoden. S i t z . - B e r . Akad. B e r l i n . Is 355-81 Muller, G. W., 189^ • Die Ostracoden des Golfes von Neapel. Fauna und Fl o r a Golfes von Neanel. Monoer. 21$ l-^ t-OW. Muller, G. W., 1906a. Ostracoda. Wiss. Ereebn. ' V a l d l v i a 1 . 8s 27-15^. Muller, G. W., 1906b. Die Ostracoden der Siboga-Expedition, Siboea. Exped. Monoer. 30s 1-^0. Muller, G. W., 1906c. Ostracoden. Res. Vov. 'Belelca'. Zool., 8 pp. Muller, G. W., 1912. Ostracoda. Das T i e r r e l c h . 31s 1-^23. Muller, Grt W., 1927. Ostracoden. i n Hahdbuch der Zooloele (Kukenthal-Krumbach), 3(1)* 399-h3h. Ostenfeld, C. H., 1931. Resume observations plankton 1902-1908. Cons. Int. Explor. Mer.. B u l l . Trim, pt. ht 601-72. Paquette, R. G. and Frolander, H. F., 1956. Improvements i n the Clarke-Bumpus plankton sampler. J . Cons. Int. Explor. Mer.. 22$ 28*+-8. Paquette, R. G., Scott, E. L. and Sund, P. N., 1961. An enlarged Clarke-Bumpus plankton sampler. Llmnol. & Oceanoer. 6$ 230-3. Richards, F. A. and Corwin, N., 1956. Some oceanographic a p p l i -cations of recent determinations of the s o l u b i l i t y of oxygen i n sea water, Liiqnoi T & Oceanoer.. Is 263-7* Rome, R., 19^2. Ostracodes marins des environs de Monaco.jBull. Inst. Oceanoer. Monaco. 8l9s 1-31. 127 Salmon, J. T., 19^ 9• New methods In microscopy for the study of small insects and arthropods. Trans. Roy. Soc. N.Z.. 77* 250-3. Sars, G. 0., 1928. Ostracoda. An account of the Crustacea of Norway, 9> Bergen Museum, 277 pp. Skogsberg, T., 1920. Studies on marine ostracods, pt. I, Zool. Bidr. Uppsala (supplement), 78^  pp. Skogsberg, T., 19^-6. Ostracods. Rep.Sars N. A t l . Deep Sea Exped.. 5* 1-26. Smith, V. Z., 1952. Further Ostracoda of the Vancouver Island region. J. Fish. Res. Bd. Can.. 9: 16-M-l. Snedecor, G. W., 1956. S t a t i s t i c a l methods applied to experiments in agriculture and biology. Iowa State College Press, Ames, 53*+ pp. Stephensen, K., 19^ 3* Marine Ostracoda, parasitic and semiparasi-t l c Copepoda and Cirripedia. Zoology of east Greenland. Medd. Gr/Snland. 121(9): 1-2^ . Strickland, J.D.H., 1958. Solar radiation penetrating the ocean. J. Fish. Res. Bd. Can.. 15: 5^3-93. Strickland, J.D.H., and Parsons, T. R., 1961. A manual of sea water analysis. B u l l . Fish. Res. Bd. Can.. 125: 1-185. Sylvester-Bradley, P.S., 19M-1. The shell structure of the Ostra-coda and i t s application to paleontological investiga-tion. Ann. Mae. Nat. Hist., ser. 11, 8: 1-33* Tabata, S., McAllister, C. D., Robertson, D. G., and Hollister, H. J., i960. Data record, Ocean Weather Station "P" (latitude 50° 00* N., longitude 1^ 5° 00* W.). Flsh.Res. Bd. Can.. MS ser.(Oceanographic & Limnologicall. 59: 1-366 (mimeog.). Tchindonova, F. C«, 1959. Feeding of some groups of macroplank-ton in the northwestern Pacific. Akad. Nauk SSSR.. Trans. Inst. Oneanologil Trudy. 30: 166-89. Vavra, V., 1906. Die Ostracoden (Halocypriden und Cypridinen) der Plankton-Expedition. Ergebn. Atlant. Plankton exped.. 2: I-76. W&borg, K. F., 195*+. Investigations on zooplankton in coastal and offshore waters of western and northwestern Norway, with special reference to the copepods. Fiskeridlr.Skr. Havundersak.. 11(1): 1-2U-6. Winsor, C. P. and Clarke, G. L., 19^ 0. A s t a t i s t i c a l study of variation i n the catch of plankton nets. J.Mar.Res.. 3(1): l-3*u 128 Winsor, C. P. and Walford, L. A . , 1936. Sampling variation in the use of plankton nets. J. Cons. Int. EXPlor. Mer.. 11* 190-20*+. Yentsch, C. S. and Duxhury, A. C•, 1956• Some of the factors af f e c ting the ca l i b r a t i on number of the C iar ke-Bumpus quantitative plankton sampler. Limnol. & Oceanogr.. l(i+): 2 6 8 - 7 3 . Youden, W. J., 1951. S t a t i s t i c a l methods for chemists. John Wiley & Sons, N.Y., 126 pp. T A B L E S 130 TABLE I CHARACTERISTICS SEPARATING..Conchoecia elegans Sars from Conchoecia dlscophora Muller Oafter Muller, 1906a) Conchoecia elegans Conchoecia dlscophora Principal seta of mi ale f i r s t antenna Distal portion of seta not tubular and thin walled Distal to oval organ the seta is very delicate and tube-like , making length deter-mination d i f f i c u l t . Endopodite of male second antenna Terminal setae (f & dis-t i n c t l y different in length, not enlarged at the base* Terminal setae (f & g) on the second segment subequal, swo-lle n at the base (esp. on right limb). Relative lengths of f i r s t antenna and frontal organ in female Tip of f i r s t antenna exceeds the starting point of the capitulum of the frontal organ; i.e., the frontal organ is relatively short* F i r s t antenna is somewhat lon-ger than half the frontal or-gan; i.e., the frontal organ is relatively long. 131 Table 2 _ Growth factors of Conchoecia elegans Sars and Conchoecia  pseudohamata n.sp. Stage 1 2 3 . h 5 6. 7, Conchoecia elegans Mean length t 1.68 1.^6 0.88 0.55 o.i+o 0.27 1 0.23 1.60 1.16 ,0.78 Growth fac tor 1.55 ! , , i. 8 1.38 j 1.1+8 j 1.17 1.38 1.1+9 j 1 # Conchoecia pseudohamata Mean length 1.96 1.63 1.11 0.77 0.5*+ 0.39 0.33 2.15 Growth B 1.20 1.1+7! 1.1+2 | i . 3 8 ; 1.18 length 1.32 I L L U S T R A T I O N S 133 P L A T E I Ostracoda F i g . 1 — Female of Conchoecia pseudohamata with s h e l l removed, viewed from r i g h t . f.o. - f r o n t a l organ ant. 1 - f i r s t antenna a n t . 2 - sec ond antenna end. - endopodite of second antenna mand. - mandible lab . - labrum max. .-. maxilla -limbic - f i f t h limb limb 6 - s i x t h limb v i b . - vibratory plates of limbs 5 & 6 limb 7 - seventh limb c.f . - caudal furca Paradoxostoma striuneulum Smith .Fig. 2—> Peristome, viewed from right« JLips - l i p s _bas. - basal process of mandible frm - chitinous frame-work of peristome -Fig. 3 — . F i r s t and second antennae, medial view. -ant. 1 - . f i r s t antenna c l . ^- terminal claw ,ant. 2 - seeond antenna ex. - exopodite of ,end. - endopodite of ant. 2 and. 2 ,Fig. h — D i s t a l portion of mandibular palp. ant. - anterior post. - posterior F i g . 5 — Ventral process of maxilla, medial view. v i b . pr. - v e n t r a l l y extended process of vibratory plate p r . l - f i r s t d i s t a l process of maxilla pr.2 - second d i s t a l process of maxilla pr . 3 - t h i r d d i s t a l process of maxilla 1.0 mm. c l. P L A T E I I3fc ELATE I I Paradoxostoma striuneulum Smith (cont'd) Fig. 6 — F i f t h , sixth, and seventh limbs, medial view. limb 5 - f i f t h limb limb 7 - seventh limb limb 6 - sixth limb Fig. 7 — Penis and caudal furca, viewed from right. c.f, - caudal furca a - v . f l , - antero-ventral f.sp. - spines of caudal appendage (flap) furca p-d . f l . - postero-dorsal pen. —penis appendage (flap) Bhilomedes sp. Fig. 8 — Shell intact with animal, viewed sli g h t l y dorsally -from right. r . - rostrum r.sin. - rostral sinus Fig, 9 — Frontal organ, viewed slightly dorsally from l e f t . Fig.10 — F i r s t antenna, medial view. Fig.11 — Distal segments of f i r s t antenna, medial view. If. - fourth segment 6. - sixth segment 5. - f i f t h segment s.s. - sensory seta P L A T E 135 PLATE I I I Philomedes sp. (cont'd) F i g . 12 — Endopodite of second antenna, medial view. 1. - f i r s t segment 3» - t h i r d segment 2. - second segment F i g . 13 — D i s t a l portion of seventh limb d.s. - d i s t a l seta m.s. - marginal seta F i g . Ik — Caudal furca, viewed from l e f t . Conchoecia elegans Sars F i g . 15 — S h e l l of male, viewed from l e f t . r . - rostrum sp. - spines of r i g h t r . s . - r o s t r a l sinus valve F i g . 16 — S h e l l of female, viewed from l e f t . F i g . 17 — Postero-dorsal extremity of open s h e l l of male ve n t r a l view. 1. asm. - l e f t asymmetric gland d-m. - pores of dor so-medial group of glands m. - medial gland pore P L A T E m 136 P L A T E I V Conehoecia elegans Sars (cont'd) F i g . 18 — Cross-section of v e n t r a l margin of l e f t valve, p o s t e r o - l a t e r a l view. i n . - inner margin f l . - flange l i . - l i s t gr. - granular sv. - selvage material F i g . 19 — F r o n t a l organ and r i g h t f i r s t antenna of male. pap. - capitulum sft., - shaft r . — r e t i n a c u l u m a. - seta a F i g . 20 — F r o n t a l organ and viewed from l e f t . cap. - capitulum s f t . - shaft b. - seta b e. - seta c a. - seta d e. - seta e (prin-c i p a l seta) ov. - oval organ r i g h t f i r s t antenna of female, d. s. - dorsal seta e. - p r i n c i p a l seta F i g . 21 — "Oval organ" and portion of p r i n c i p a l seta of male f i r s t antenna. prox. - towards proximal end of seta d i s t . - towards d i s t a l end of seta P L A T E IDT. 137 PLATE V Conehoecia elegans Sars (cont'd) F i g . 22 — Endopodite of male second antenna, medial view. JF. - seta f pr.mam. - processus "g. - seta £ mammlllaris d.mam. - d i s t a l mam-mi l l a F i g . 23 — Endopodite of r i g h t second antenna of male, medial view. •pr.mam. - processus mammlllaris d. - seta <| •d.mam. - d i s t a l mamilla f . - seta f -a. - seta £ g. seta jg. ^b. - seta b hk. - hook of t h i r d - seta c, segment h. - seta h, i . - seta 1 j . - seta X F i g . 2k — Endopodite of l e f t second antenna of male, medial view. F i g . 25 — Endopodite of female second antenna, medial view. pr.mam. - processus mammlllaris h. - seta h, d.mam. - d i s t a l mammilla 1. - seta ± f . - seta £ j . seta j, g. - seta £ P L A T E 3ZT 138 PLATE VI -Conchoecia eleeans Sars (cont'd) F i g . 26 — Labrum viewed from l e f t . cav. - concavity cmb. - comb c.th, - chitinous thickening F i g , 27 — Labrum, ve n t r a l view. p i . - hyaline plate cmb. - comb c. th. - chitinous thickening F i g . 28 — Faragnaths and l e f t maxilla, quasi-anterior view. prg. - paragnath bas. - basale pcox. - procoxale end. - endopodite cox. - coxale c l , - c l e f t i n end of coxal endite F i g . 29 — D i s t a l segment of l e f t maxilla, l a t e r a l view. F i g . 30 — Mandible of female, medial view. cox. - coxale ex. - exopodite bas, - basale e p i . - epipodial ap-end. - endopodite pendage F i g . 31 — Coxal endite of mandible, medial view. t . r . - toothed ridge p.t-1 - proximal tooth-d. t . - l . - d i s t a l t o o t h - l i s t l i s t pad. - masticatory pad P L A T E 3ZZ 139 PLATE VII Conehoecia elegans Sars (cont'd) F i g . 32 — F i f t h limb, l a t e r a l view. v i b . - vibratory plate prot. - protopodite p.edt. - proximal endite d.edt. end. ex. F i g . 33 — S i x t h limb of male, medial view, v i b . - vibratory plate prot. - protopodite end. ex. F i g . 3*+ — S i x t h limb of female, medial view. prot. - protopodite v i b . - vibratory plate end. ex, - d i s t a l endite - endopodite - exopodite remnant of endopodite exopodite remnant of endopodite exopodite F i g . 35 — Penis and caudal furca viewed from l e f t , §P< copulatory appendage P L A T E 3ELT PIATE VIII ^Conchoecia pseudohamata n. sp. F i g , 36 — S h e l l of male viewed from r i g h t . r . - rostrum r.asm. - pore of r i g h t r . s i n . - r o s t r a l sinus asymmetric gland F i g . 37 — S h e l l of female viewed from r i g h t . F i g . 38 — S h e l l of male, dorsal view. F i g . 39 — S h e l l of male, v e n t r a l view. F i g . hO — Posterior margin of open s h e l l of male, ventral view. r.asm. - r i g h t asymmetric gland l.asm. - l e f t asymmetric gland d-m. - dorso-medial group of glands F i g . hi — Posterior margin of open s h e l l of female, ve n t r a l view. r.asm. - r i g h t asymmetric gland l.asm. - l e f t asymmetric gland med. - medial gland pore - l a t e r a l gland pores l a t . med. - medial gland pore l a t - l a t e r a l gland pores 0.8 mm. . 6 mm . P L A T E VTTT PLATE TX Gpnchoecia pseudohamata n.sp. (cont*d) F i g . k2 — Fron t a l organ and r i g h t f i r s t antenna of male, viewed from r i g h t . p . s f t . 1- basal subdivision of proximal part of shaft p . s f t , 2- d i s t a l subdivision of proximal part of shaft d . s f t . - d i s t a l part of shaft d. - seta & cap. - capitulum e. - seta e, r . - retinaculum x-x - delimits equip-a. - seta a ment of d b. - seta b *-* - delimits equip-c. . - seta c, ment of e F i g . *+3 — Fr o n t a l organ and r i g h t f i r s t antenna of female viewed from l e f t . cap. - capitulum e. - seta e, (prin-s f t . - shaft c i p a l seta) F i g . — Processes on a portion of p r i n c i p a l seta of male f i r s t antenna. d i s t . - towards d i s t a l end of seta prox. - towards proximal end of seta F i g . k$ — Process of p r i n c i p a l seta of male f i r s t antenna. F i g . k6 — Endopodite of l e f t f i r s t antenna of male, medial view. f . - seta X i . seta h g. - seta £ o« seta j . h. - seta h P L A T E I X lk2 PLATE X 'Conehoecia pseudohamata n.sp. (cont'd) F i g . k? — Endopodite of r i g h t second antenna of male, medial view. 1. - f i r s t segment e - seta e 2. - second segment pr.mam - processus 3. « t h i r d segment mammlllaris a-. - seta a d.mam. - d i s t a l mammilla b. - seta b hk. - hooked portion e. - seta £ of t h i r d seg-d. - seta & meht F i g , *f8 — Endopodite of l e f t second antenna of male, medial view. F i g . *+9 — Endopodite of female second antenna, medial view. a, - seta a b. - seta b e. or d.- seta representing setae c, or d, of male - seta f h. 1. j . pr .mam.-d.mam. -seta £ seta h seta X seta 2. processus mam-m l l l a r i s d i s t a l mammilla F i g . 50 — Labrum viewed from l e f t . cmb. - comb gr. - groove F i g . 51 —' Labrum, ve n t r a l view, cmb. - comb gr. - groove p i , - hyaline plate P L A T E X lh3 PLATE XI 5 Conehoecia pseudohamata n.sp, (cont'd) i F i g . 52 — Paragnath and maxilla, medial view, pcox. - procoxale end, - endopodite _cox, - coxale prg. - paragnath _bas. - basale c l . - c l e f t i n end of coxal endite F i g , 53 — Proximal extremity of mandible, medial view, ~k. - k e e l - l i k e process F i g . 5*+ — Coxal endite of mandible, dorso-medlal view, t , r , - toothed ridge p . t - 1 , - proximal tooth-e d , t - 1 - d i s t a l t o o t h - l i s t l i s t pad, - masticatory pad Pig* 55 — Penis and caudal furca viewed from r i g h t , ap, - copulatory appendage unpd. - unpaired b r i s t l e Growth Stages F i g . 56 — Caudal furea of Conehoecia elegans. five-clawed stage. ..Fig, 57 — Caudal furca of Conehoecia pseudohamata. three-clawed stage. pap, - p a p i l l a (rudimentary claw) P L A T E X I F i g , 58 Approximate s h e l l lengths f»r the growth, stages of Conchoecia elegans, Sars and £ pseudohamata n*sp* f»und In Indian Arm* Stages distinguishable by the number »f f u r c a l claws species designated with the a i d of s h e l l length measurements* CLAWS PER G R O W T H CAUDAL S T A G E FURCA C o n e h o e c i a e l e g a n s • I •2 •3 •4 •5 •6 •7 8 7 6 5 4 3 2 (10) i [T] =~i (io) a"7 - ^  " I - J - I (16) • (28) • (21) „ => (10) •2-5 # n (8) • (15) •3 5- ' (10) J (3) •6- / C (2) • C o n e h o e c i a p s e u d o h a m o t a P A R A M E T E R S (15) •5-• (16) (2) , n (is) -6-(7) • (2) MEAN RANGE THREE SAMPLE STANDARD DEVIATIONS SAMPLE STANDARD ERROR SAMPLE SIZE —i i 1 1 r i i 1 1 i 1 i i 1 i 1 i 1 1 1 i 1 i 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 I.I 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 LENGTH OF S H E L L (MM.) ]>5 F i g * 5 9 ~—Frequency of s h e l l lengths among growth stages 1 (male & female), 2, and 3 of Conchoecia eleeans Sars* Ih6 F i g * 60 Approximate s h e l l lengths of specimens of Gdnchoecla  elegans Sars co l l e c t e d from sarious B r i t i s h Columbia Inlets* For parameters employed see F i g * 58» R E G I O N P A R A M E T E R S S A M P L E S I Z E S E X I N D I A N A R M B U T E I N L E T K N I G H T I N L E T M U C H A L A T I N L E T A L B E R N I I N L E T I - 4 ^ — ^ 5 | TOFI NO I N L E T H E R B E R T I N L E T 4 5 S A A N I C H I N L E T I -ttt- I 1.00 1.20 L E N G T H 1.40 1.60 ( M M.) 1.80 61 Approximate shell lengths of specimens of Conchoecia pseudohamata n« sp* collected from Station nP" and various British Columbia inlets* For parameters employed see Fig, 58* R E G I O N P A R A M E T E R S S A M P L E S I Z E S E X ? I 6 I 6 5 3 5 5 a* S T A T I O N " P " I N D I A N A R M B U T E N L E T K N I G H T I N L E T 5 5 5 5 a" M U C H A L A T INLET 1 . 6 0 2 . 0 0 2 . 2 0 2 . 4 0 L E N G T H 2 . 6 0 ( M M . ) 2 . 8 0 3 . 0 0 3 . 2 0 ]>8 • 6 2 Indian Arm i n p lan view and l o n g i t u d i n a l p r o f i l e (after G i l m a r t i n , I960)* Numbers designate s tat ions where oceanographic data were co l lec ted* Hor i zonta l bars mark locat ions from which plankton was sampled. F i g * 6 3 . — L o n g i t u d i n a l , p r o f i l e s of the d i s t r i b u t i o n of temperature i n Indian Arm for selected months of I 9 6 0 . Isotherms i n C , those of thermocline l a r g e l y omitted. S T A T I O N 2 6 9 12 15 23 J I I I I l _ F i g * 6U«-Longitudinal p r o f i l e s of the d i s t r i b u t i o n of s a l i n i t y i n Indian Arm for ,_, selected months of I960, Isphallnes i n °/oo, those of halocline largely omitted, S T A T I O N F i g * 65 •*•» The density of deep water at Station. 6 during i960,. Means of ?l values from 100, 150, and 200 m* depths. . ' vn' t 152 F i g * 6 6 ~« The v e r t i c a l d i s t r i b u t i o n of dissolved oxygen at Station 6 during I 9 6 0 * CL LU Q 0 65 125 200 f / J A N . V 1 • 0 65 125 200 0 65 125 200 0 65 125 200 o so 100 ISO 10 F E B . 10 M A R . 10 A P R . o--50--100-I50--0--60--100-I 50--0--SO I 00-I60--10 0 X Y G E N 1 1 V M A Y < 1 1 1 1 1 ( mg./ I.) 10 J U L . 10 S E P . 10 NOV. 10 C o n c e n t r a t i o n a t a s t a n d a r d d e p t h • Mean c o n c e n t r a t i o n , over an i n t e r v a l of d e p t h C S o l u b i l i t y — o 153 F i g * 67 T i d a l curves and times at which stations were occupied i n i 9 6 0 * Stations shown as v e r t i c a l strokes* Curves from Data Rep»rt 18, I n s t i t u t e of Oceanography, University of B r i t i s h Columbia (Anon*, 1961)* 7.5 5 A 2.5 cr UJ UJ 2.5H 0 x UJ x 5H 2.5 0 5 ^ J A N . 6 F E B . 15 M A R . 2 3 A P R . 2 0 J A N . 7 M A R . 24 15 1 2 0 0 0 0 0 0 1200 T I M E I N H O U R S F i g * 68 T i d a l curves, continued fr«n F i g * 67 » TIME IN HOURS F i g , 6 9 •*.-* Longitudinal p r o f i l e s of temperaturesand s a l i n i t y d i s t r i b u t i o n s occurring i n March, I960, during periods when r i s i n g tides of various heights occurred. M Isotherms (°C) and isohalines (°/oo) l a r g e l y omitted from thermo* and halo** V J I c l i n e s * F i g , 70 —. Depths of l i g h t penetration at Stations 6 and 9 at times corresponding f those of daylight plankton c o l l e c t i o n s i n i 9 6 0 * I I I I I 1— JAN. MAR. MAY J U L . SEPT. NOV. 157 F i g * %1 — Depths of quartiles f o r the v e r t i c a l d i s t r i b u t i o n of Conchoecia elegans Sars at Station 6 and 9 i n I960* STATION 6 STATION 9 ,158" F i g * 72 -»~ Depths of quartiles for the v e r t i c a l d i s t r i b u t i o n of Conchoecia pseudohamata n*sp* at Stations 6 and 9 i n I960. F i g * 73 V e r t i c a l d i s t r i b u t i o n of growth stages of Conehoecia elegans Sars at Station 9> over a "2*f-.hour" cyle i n July, I960, Concentrations are divided to show the vn r e l a t i v e proportions of the f i r s t (adult £ and 9-), second (2), t h i r d .(3)» and ^ fourth (h) stages of growth* INDIVIDUALS PER 40 LITERS 1133 - 1228 JULY 26 MESH — 0.40 MM. 141 I - I 505 JULY 2 5 MESH - 0.12 MM. 1625 - 1712 JULY 27 MESH - 0.40 MM. 160 F i g . 7k -« V e r t i c a l d i s t r i b u t i o n of growth stages of Conehoecia  pseudohamata n.sp* at Station 9» over a "2*f hour" cycle i n July, I960. Concentrations are divided to. show the r e l a t i v e proportions of the f i r s t (adult j$ and $).. second ( 2 ) , t h i r d ( 3 ) , fourth (*+), f i f t h (5), s i x t h ( 6 ) , and seventh (7) stages of growth* I 707 - 1758 INDIVIDUALS PER 40 LITERS 161 F i g * 75 ~™ V e r t i c a l d i s t r i b u t i o n of Conchoecia pseudohamata n#sp* continued from F i g * 7*+* INDIVIDUALS PER 40 LITERS 162 F i g * 76 — V e r t i c a l d i s t r i b u t i o n of Conehoecia pseudohamata n.sp*, continued from F i g * 75» . . . 1 1 3 3 - 1 2 2 8 J U L Y 2 6 M e s h - 0 . 4 0 mm I 2 0 H I 4 I I - I 5 0 5 J U L Y 2 5 M e s h - 0 . 1 2 m m . 1 6 2 5 - 1712 J U L Y 2 7 M e s h - 0 . 4 0 m m . i n r 2 3 4 I N D I V I D U A L S P E R 4 0 L I T E R S 163 F i g * 77 The depth of l i g h t penetration against the depth of the f i r s t q u a r t i l e of.the v e r t i c a l d i s t r i b u t i o n of Conchoecia elegans Sars at Stations 6 and 9 for selected months of i 9 6 0 * 6 0 n c i 4 0 A S T A T I O N 6. o MAR. O JAN. o JULY ° NOV. o MAY 2 0 X 6 0 oSEPT. S T A T I O N 9. O MAR. o JAN. X r-a. UJ o 4 0 A o S EPT. © J U L Y -b NOV. o MAY 2 0 100 -I— 10 120 130 140 D E P T H (nrO 1st Q U A R T I L E , V E R T I C A L D I S T R I B U T I O N 161+ F i g * 78 ~-- D i s t r i b u t i o n of Conchoecia elegans Sars on tranverse p r o f i l e s across Indian Arm at Stations 2, 6 , and 12 during daylight i n July, i 9 6 0 * S T A .2 STA .6. S TA . I 2 CENTRE DISTR. — L'.IIZ <0.l INDIV./40L. — I I 0.1—0.9 INDIV./40L. — >0.9 INDIV./40L. — STATION POSITION — 1 .165 F i g * 7 9 -*» D i s t r i b u t i o n of Conchoecia pseudohamata n.sp* £»n transverse p r o f i l e s across Indian Arm at Stations 2 , 6 , and 12 during daylight i n July, I 9 6 0 * S T A . 2 S T A . 6 S T A . I 2 CENTRE DISTR. — L...J <0.l INDIV./40L. — 1 I 0.1-0.9 INDIV./40L. — E33 >0.9 INDIV./40L. — V777A STATION POSITION — 1— . 80 W D i s t r i b u t i o n of Conchoecia eleeans Sars at night, on longitudinal p r o f i l e s of Indian Arm during I960, O N ON S T A T I O N S 2 6 9 12 IS 23 2 6 9 12 ' l5 23 J I I I I I T I I I 1 1 1 J I I I I 1 - , I I 1 1 1 1 CENTRE DISTR - 'C.'.l <O.I INDIV. /40 L. — CZZ3 0.1-0.9 INDIV./40L. - >0.9 INDIV/40L. — SZZZ, F i g * 81 **-»• Distribution of Conchoecia pseudohamata n ssp, a t night, on longitudinal p r o f i l e s of Indian Arm, during i 9 6 0 . ON CENTRE DISTR — l~Z <0.l INDIV. /40L. — • 0. I - 0.9 IN DIV. /40 L. — WM >0.9 INDIV /40 L . — ^2 F i g * 82 — Concentrations of Conchoecia.elegans Sars at various stations along Indian Arm showing proportions of, growth stages numbered 1 (j3 and ?), . :: 2 , and higher than 2* Data from night c o l l e c t i o n s i n i 9 6 0 * M : " • . ' ON 00 STATION NUMBER F i g * 83 Concentrations of Conchoecia elegans Sars at various stations along Indian Arm showing proportions of growth stages numbered 1 £ Or? and $), 2 , and higher than 2.: Data from day l i g h t - c o l l e c t i o n s i n i 9 6 0 * ^ i.OH cr UJ o ^ 1 .0 J S T A T I O N N U M B E R ;, 8*+ «-* Concentrations of Conchoecia pseudohamata n,sp* at various stations along Indian Arm showing proportions of growth stages numbered 1 and 9 ) , 2 , 3 , and higher than 3* Data from night c o l l e c t i o n s i n i 9 6 0 * S T A T hO N NUMBER F i g * 85 Concentrations of Conchoecia pseudohamata n#sp* at various stations along Indian Arm showing proportions of growth stages numbered 1 ip and ?), 2 , 3 , and higher than 3* Data from daylight c o l l e c t i o n s i n I960* T r in cc STATION NUMBER 172 F i g , 86 — Occurrences of Conchoecia elegans Sars at 15 and 23 during; I960. S T A T I O N 15 0 25 50 L J U N . ( N , f ) J U L . (D,e) S E P T . ( N , f ) O C T . ( D , f ) N O V (N, f ) (N,e) 0 . LU Q 0 20 0 20 J A N . S T A T I O N 2 3 F E B . M A R . A P R . (N ,e ) M A R . ( D , e ) N N J U N . ( N , f ) J U L . ( D,e) S E P T . ( N , f ) O C T . ( D,e) N O V . ( N , f ) (N,e) T I M E : n igh t - N day • - D Not sampled - o L 0 0.1 0.2 1 nd i v. / 4 0 I. T I D E : f l o o d - f ( r i s ing) e b b - e . ( f a l l i ng ) 173 F i g , 87 — Occurrences of Conchoecia pseudohamata n*sp«at Stations 15 and 23 during I960, S T A T I O N 15 0 -2 5 -5 0 - J AN . ( N , f ) FEB. ( N , e ) MAR. ( N , f ) APR. ( N , f ) 1 MAY (N ,e ) (D,e) 0 • 2 5 -5 0 - JUN. (N, f ) JUL. (D,e) SEPT. ( N , f ) OCT. ( D , f ) NOV. (N,f) (N,e) Q. LU O 0 2 0 0 2 0 o o S T A T I O N 2 3 o o o o JAN. FEB. MAR. APR . (N,e ) MAR . ( D,e) JUN. ( N , f ) JUL. ( D,e) SEPT. ( N , f ) OCT. ( D , e ) NOV. ( N, f ) (N,e) T I M E : n igh t - N day - D Not sampled — o L _L J 0 0.1 0.2 i n d i v . / 4 0 I. T I D E : f I ood - f. ( r is ing) ebb — e. ( f a l l i n g ) 17*+ Fig* 88 —- Average concentrations of Conchoecia elegans Sars and Cm pseudohamata ru sp* in Indian Arm during selected months of I960* 1.0 or U i O co _ i <i o a z 0.5 H C o n e h o e c i o e l e g a n s S a r s ^ *• J A N . MAR MAY J U L . -cu. S E P . NOV. I g C o n e h o e c i o p s e u d o h o m a t a n. sp. co oc _ i 1.0-| o CO _ l <I > J A N . M A R . MAY J U L S E P . NOV. I n d i v i d u a l s in a l l g r o w t h s t a g e s o— A d u l t s o-F i g * 8 9 The proportion of adults to individuals i n a l l stages and §he proportion of females having most of |helr eggs mature, f o r Conehoecia elegans Sars i n Indian Arm during I960* I—a F i g , 90 «- The proportion of adults 3 to individuals In a l l stages and the proportion 70 of females hating most of their eggs mature, f o r Conehoecia pseudohamata n.sp* i n Indian Arm during i 9 6 0 . A P P E N D I C E S 1 APPENDIX I. CALIBRATION OF CLARKE-BTJMPUS' PLANKTON SAMPLERS IN THE FIELD 1 INTRODUCTION During i960 the Insti t u t e of Oceanography, University of B r i t i s h Columbia, conducted zooplankton studies i n Indian Arm, a coastal i n l e t of B r i t i s h Columbia. Quantitative int e r p r e t a t i o n of the re s u l t s required that the Clarke-Bumpus plankton sam-plers used be cali b r a t e d to determine rates of flow through them f o r the conditions i n which they were employed. Clarke and Bumpus (1950), who described the sampler, ca l i b r a t e d i t f o r flow using known volumes of water. Yentsch and Duxbury (1956) als o c a l i b r a t e d i t using known volumes, but incorporated ap-paratus designed to minimize possible r e s t r i c t i o n s i n flow imposed by the conventional flume previously used. Winsor and Clarke (19^ 0) and Wiborg (195*+) included the Clarke-Bumpus sampler i n comparisons of the r e l a t i v e e f f i c i e n c i e s of various plankton samplers. Paquette and Frolander (1956) suggested modifications to improve the opening-and-closing mechanism of the sampler. Paquette, Scott and Sund (1961) enlarged the aperture of the sampler and, among other innovations, replaced the impellor-veeder counter type flow-meter by one with a free-flooding, gear-driven d i a l r e g i s t e r . In the present i n v e s t i g a t i o n the samplers were calibrated 1 McHardy, 1961. 2 i n the f i e l d where they were towed at a speed higher than those corresponding to the rates of flow used by Yentsch and Duxbury (1956). In addition to the c a l i b r a t i o n tows conducted during regular cruises to Indian Arm, a s p e c i a l program was designed to acquire more precise values. This included tests f o r differences between i n d i v i d u a l samplers and f o r the e f f e c t of the d i f f e r e n t sizes of mesh used i n their nets. Provision was also made for an evaluation of the possible e f f e c t of currents. APPARATUS The Clarke-Bumpus plankton sampler consists e s s e n t i a l l y of a metal cylinder with a door at the leading end, a recording impellor (flow-meter) i n the middle, and a c o n i c a l net at the t r a i l i n g end. The readings of meters on the samplers used i n the present invest i g a t i o n (e.g. readings i n Table 1) d i f f e r by a factor of ten from those reported by other workers. A 10:1 reduction i n the gearing of the flow-meters caused each count to represent 10 revolutions. One sampler, CB-3, had a 1:1 r a t i o of meter-reading to revolutions, but i t s readings were adjusted to agree with those of the other samplers. To convert to revolutions of the impellor, counts may be mul t i p l i e d by ten. A l l samplers used were of conventional si z e (12.3 cm. diameter opening) and possessed the modifications recommended by Paquette and Frolander (1956). 3 PROCEDURE S t a t i s t i c a l To invest igate di f ferences between samplers, between meshes, and between the d i rec t ions of towing, the c a l i b r a t i o n program was designed so that i t s r e s u l t s could be tested by s t a t i s t i c a l means. To avoid bias a l l poss ib le combinations of mesh s i ze and sampler were arranged i n a randomized block des ign. I d e a l l y each sampler should have been associated with a s i ze of mesh not found on the other samplers being towed a t the same time. However, because the number of mesh s izes (h) was less than the number of samplers (5), one of the mesh s izes had to be repeated during each tow. Four d i f f e r e n t sampler-mesh com-binat ions were required so that each sampler could become as-soc iated with every mesh s i z e . Tests on the four combinations were completed w i th in e ight hours during d a y l i g h t . S t a t i s t i c a l d u p l i c a t e s , required for te s t ing i n t e r a c t i o n (Table 1), were obtained during the fo l lowing day by a r e p l i c a t i o n of the tests on the ent i re four combinations. Weather and sea condit ions during the second day were s i m i l a r to those of the f i r s t day. To account for any e f f e c t caused by towing with or against movement of the water, each tow and i t s combination of samplers and meshes was Immediately fol lowed by a tow i n the opposite d i r e c t i o n . When towed a standard distance over the bottom against a steady current , the amount of water f i l t e r e d by a sampler would be greater than when towed i n the absence of such a current} conversely, when towed in the same direction as a current, less would be f i l t e r e d than would be expected were no current present. Consequently, by towing in opposite directions i t was possible to recognize and measure any differences in rates of f i l t e r i n g due to a current, assuming i t to be steady. The calibration procedure was simplified by attaching the samplers to the towing wire in the same order each time. This arrangement could have introduced bias with respect to the ver t i c a l distribution of currents, but such was not suggested by the Analysis of Variance (see Results). The s t a t i s t i c a l significance of variation from different sources was established by the Analysis of Variance (Table 1). Variables regarded as possible sources were: (1) samplers, (2) sizes of mesh, and (3) directions of towing. When the calculated "F" (mean square of the source divided by mean square of error) was found to be higher than the "F" expected by chance (F for .95 and .99 levels of confidence, Table 1), then a s t a t i s t i c a l significance was assigned to that source. Field Because Indian Arm, locale of the zooplankton investigation, was temporarily covered by fog, the special calibration t r i a l s were conducted in a neighbouring inlet, Howe Sound. A group of islands surrounded the selected area and provided effective 5 shelter from the prevailing down-inlet wind. The path to be towed was over latitude ^9° 25.8» N. between longitudes 123° 2*+.M W. and 123° 22.6 1 W., i n water about 180 m. deep, and aligned between two prominent points of land which served as fixes from which distance could be measured by radar. The procedure for towing the samplers was similar to that used i n Indian Arm plankton collections except for the reduced spacing between samplers and the measurement of the distance towed rather than i t s duration. Five Clarke-Bumpus samplers were attached to hydrographic wire on which was hung a weight of about 100 lbs. They were spaced at intervals of five metres and lowered u n t i l 55 m. of wire separated the top sampler from the meter-block (on the ship). When the ship had reached the starting point, the samplers were opened, towed over a five cable (about 930 m.) distance measured by radar, then closed and retrieved. The procedure was the same for a l l tows. To verify that distances as measured by radar were reasonably accurate, the data of the present calibration program were compared to those of other t r i a l s . Tows taken over a 6-cable distance measured by another radar set, as well as some taken along a 10-cable distance marked by fixed range-markers gave results comparable (± 2$) with those obtained in Howe Sound. Due to i t s indirect nature, however, this evidence does not provide strong verification ofthe accuracy of the distance towed. To accomodate possible error, therefore, the distance has been considered accurate within i 5%» 6 Wire-angle rather than engine-speed was used in estimating the ship's speed through the water in order to account for the influence of external forces. The angle of the towing wire, caused by its resistance to movement through the water, was maintained at 35° and at this angle the calculated speed through the water was 2.*+ knots. Variation, attributable mainly to the difficulty of adjusting engine speed, was 0.8 standard deviations from a mean of 12.5 minutes and, is considered to have had negligible effect on the results. Two possibly adverse affects — the variability of flow due to wind-driven surface-water and the reduction of flow due to the net being clogged by highly concentrated phytoplankton in the upper waters — were minimized by towing the samplers below 50 m. Even at this depth phyto-plankton accumulated on the sides of the nets but, judging from past experience and from readings of the flow meters, the amount was insufficient to cause clogging. To lessen the possibility of effects from vertical current gradients, the samplers were confined to a depth-range of 20 m. RESULTS Differences between counts recorded by the flow-meters of the individual samplers, and by the meters of samplers with and without the attachment of nets of various mesh sizes, were shown by Analysis of Variance to be statistically significant. Neither i n t e r a c t i o n nor the e f f e c t of d i r e c t i o n of towing showed s i g n i f i c a n c e . This Analysis, together with Means fo r Samplers and Means for Meshes, i s presented i n Table 1. Comparison of those calculated F*s and expected F f s which represent Interactions suggests that some d i s s i m i l a r i t y e x i s t s between samplers with regard to their behavior towards the various meshes (S x M, Table 1). At the .95 l e v e l of confidence, however, such i s not shown to be s i g n i f i c a n t . The lack of s i g n i f i c a n t i n t e r a c t i o n between samplers and directions (S x D, Table 1) indicates that r e s u l t s were not biased by the possible e f f e c t of a v e r t i c a l current gradient being associated with the constant arrangement by which samplers were attached to the towing wire. V i s u a l inspection indicated that r o t a t i o n of the impellor i n CB-6 was less free than i n the other samplers. Although the mean f o r CB-6 was low, i t did not appear from the Means f o r Samplers (Table 1) to d i f f e r greatly from those f o r the other samplers. The mean of counts obtained when net # 20 (216 meshes/inch) was attached i s shown (Means fo r Meshes, Table 1) to be quite d i f f e r e n t from those obtained with other nets or with no net. In contrast, the means f o r attachment of nets # 10 (lM+ meshes/ inch) and # 2 (55 meshes/inch) and f o r no net may be regarded as unusually s i m i l a r . For net # 2 the mean of counts was higher than f o r no net. 8 DISCUSSION The results demonstrate some effects of towing speed and net attachment on the percentage of water accepted by the sampler and on the calibration value of the flow-meter of the sampler. The concept of percentage acceptance is distinct from that of calibration value. Acceptance is the proportion of the water encountered which the sampler can pass and depends on the resistance imposed by a net and on the towing speed. Calibration value is the volume-per-revolution assigned to the flow-meter in the sampler and ideally is constant. In the Clarke-Bumpus sampler, however, the latter may be altered by changes i n flow pattern caused by the attachment of nets (Yentsch and Duxbury, 1956). Percentage Acceptance Knowledge of the volume of water actually accepted by the Clarke-Bumpus sampler is essential for the determination of a calibration value. Those values acquired by the use of a con-ventional flume are from known volumes but, because of abnormal restrictions on the flow of water, are too low (Yentsch and Duxbury, 1956). Values from f i e l d calibration are usually determined from the unrealistic assumption that 100% of the water encountered over the towing distance is accepted by the 9 sampler when no net i s attached. These l a t t e r values are too high. The modified-flume method of Yentsch and Duxbury allows the water presented to the sampler to be accepted or rejected i n an unrestricted manner and, at simulated towing speeds of 0,75 to 1.5 knots, has shown the sampler to accept 9*4$ of the water presented. The volumes accepted during the tows made i n the present study are the product of the revolutions accumulated and a derived volume-per-revolution (the c a l i b r a t i o n value) which i s considered to be true (see below with regard to the value chosen). E f f e c t of Towing Speed on C a l i b r a t i o n Value and Percentage Acceptance C a l i b r a t i o n Value Yentsch and Duxbury (1956, F i g . 2) showed *f.3 l i t r e s / r e v -o l u t i o n to be the c a l i b r a t i o n value for a sampler without net attached being towed at speeds ranging from 0.75 to 1.5 knots. Their actual values lay between h*$0 and *+,36 1/rev., a range of less than 2%, Clarke and Bumpus (1950) using speeds ranging from 0.5 to k knots, obtained a range i n c a l i b -r a t i o n value of % for each of several samplers tested. 10 Extrapolation from F i g , 2 of Yentsch and Duxbury (1956), indicates that the value of *+,3 l i t r e s / r e v o l u t i o n tends to remain the same at 2,*+ knots as at 0,75 to 1,5 knots. U n t i l this has been confirmed by experimentation however, i t s use i n the present inves t i g a t i o n must be regarded with caution. Even so, the evidence from Clarke and Bumpus (1950) would suggest that the use of *+,3 1/rev, may be acceptable over a range of speed encompassing that employed i n the present study. This value has been applied below to compute the volume of water accepted by the sampler at the towing speed of 2,h knots, Percentage Acceptance The volume accepted by a sampler may be expressed as a percentage of the volume encountered:-• tSaS ^ oSntered x 1 0 0 = Acceptance Analysed, this i s expressed as :-(Calibration Value) (Mean Revolutions) 1 Q 0 (X-sectional Area Sampler) (Distance Towed) a Calculated f o r the present study, this equals:-a Area i n square decimetres, distance i n decimetres, r e s u l t i n g volume i n l i t r e s . 11 Thus the water accepted i s estimated as 79$ of that en-countered by the sampler. This percentage i s lower than Yentsch and Duxbury fs (1956) estimate of acceptance by a sampler, without net attached, being subjected to speeds of flow of 0.75 to 1.5 knots. The increase of speed to 2,*+ knots seems, therefore, to have resulted i n a s i g n i f i c a n t reduction i n the amount of water which the sampler i s capable of accepting. An a d d i t i o n a l r e s t r i c t i o n on the passage of water through the sampler may be imposed by the attachment of a net. This p o s s i b i l i t y i s considered below. E f f e c t of Net Attachment on Percentage Acceptance and C a l i b r a t i o n Value Percentage Acceptance Yentsch and Duxbury (1956) found that attachment of nets of mesh sizes 0.2*+ and 0.12 mm. (# 6 and #12) reduced acceptance to about 93$ ( i . e . by 1$) and mesh size 0.07 mm. (# 20) reduced i t to about 91$ (by 3$). Although these meshes were si m i l a r to those used i n the present study (namely, Q.hO mm. for #2 net, 0.12 mm. f o r #10 net, and 0.07 mm. f o r #20 net), their relationships to the volume accepted cannot be expected to remain the same at the higher speed of 2,h knots. I t seems safe to assume, however, that with a net attached the sampler would accept less than the 79$> considered to be accepted without any net. 12 The lower mean counts f o r net #20 (Means f o r Meshes, Table 1) indicates that the f i n e r mesh of this net has allowed less water to enter the sampler. To determine the actual amount of this reduction the volume-per-revolution ( c a l i b r a t i o n value) would have to be known. However, as shown below, this value i s a l t e r e d by the attachment of a net. The amount i t may have changed at the speed of 2.*+ knots i s not known. C a l i b r a t i o n Value Yentsch and Duxbury (1956) observed a decrease i n the c a l i b r a t i o n value caused by the attachment of nets and attributed t h i s to a change of flow pattern i n the forepart of the sampler. They considered that the water entering the sampler was being diverted from a c e n t r a l p o s i t i o n towards the peripheral regions of the impellor, thus providing a greater turning moment and causing the impellor to operate more e f f i c i e n t l y . As a r e s u l t , f o r an equivalent volume of water, the flow-meter would give a higher reading with attachment of a net than without. For their range of speeds of 0.75 to 1.5 knots, Yentsch and Duxbury (1956) demonstrated that nets of mesh sizes 0.2*+ and 0.12 mm. (#6 and #12) decreased the c a l i b r a t i o n value by 0.05 1/rev. (to 1f.2'5 1/rev., approx.), and a mesh of size 0.07 mm. (#20) decreased i t by 0.10 1/rev. (to h.20 1/rev., .• 13 : approx,). Again these r e l a t i o n s h i p s , as with those for per-centage acceptance, may not apply at 2.k knots. Due to the high mean number of counts for # 2 net (Means f o r Meshes, Table 1) the existence of a decreased c a l i b r a t i o n value can be demonstrated without having to assume some figur e f o r the volume accepted. I t seems that the # 2 net, unlike those with f i n e r mesh, did not reduce the percentage acceptance enough to mask the e f f e c t that i t s attachment had on the c a l i b r a t i o n valuej f o r , although the resistance imposed by the mesh would have reduced the volume accepted, the number of counts recorded by the meter was higher (compare Means fo r Meshes of " N i l " and #2 net, Table 1 ) . Thus with a # 2 net, a volume equivalent to or smaller than that passed without a net was able to produce a meter reading (mean value of 16 readings) which was higher, and hence a c a l i b r a t i o n value which was lower. As suggested above, this lowered c a l i b r a t i o n value may have been caused by the change i n e f f i c i e n c y of the impellor. A flow-meter with more s t a b i l i t y despite changes i n flow pattern would be preferable; perhaps that introduced by Paquette, S c o t t and Sund (1961) f o r their enlarged Clarke-Bumpus sampler w i l l be an improvement. APPLICATION TO PLANKTON Plankton density may be defined as the r a t i o of the number Ih of organisms caught to the volume of sea-water passed through a sampler, The volume of sea-water may he estimated as the product of the revolutions accumulated during a plankton tow and the volume/revolution obtained in calibrating the sampler. As suggested by Yentsch and Duxbury (1956), the calibration value of approximately h litres/revolution previously proposed by Clarke and Bumpus (1950) is probably of sufficient accuracy for the computation of plankton densities. Although not conclusively shown, evidence suggests that this value is also reasonable where towing is conducted at speeds approximating 2.1+ knots.* Studies by Winsor and Walford (1936), Barnes (19^9), and Marshall (1951) indicate that plankton sampling may be limited i n i t s accuracy by the dispersion of organisms being greater than can be explained on the basis of a normal (random) dis-tribution. Although the differences between samplers and meshes may be significant when compared to a random variation, they may appear very small when matched against the contagious types of distribution which may occur in plankton. This suggests that to take into account the differences between meshes and between samplers would be an unnecessary step in calculating the concentration of planktonic organisms. SUMMARY 1* Five Clarke-Bumpus plankton samplers were towed over a 15 distance df about 930 m. (5 cables) i n various combinations with and without nets of various mesh s i z e s . 2. S i g n i f i c a n t differences between samplers and between sizes of mesh were shown by an Analysis of Variance of the number of counts recorded by the flow-meters of the samplers. 3. The mean number of counts recorded for # 20 net (216 meshes/inch) was lower than f o r the other nets (55 and ikk meshes/inch) and f o r no net. This suggests that the f i n e r mesh of this net r e s i s t e d the flow of water and reduced the volume accepted to a greater extent than did the meshes of the other nets. k* The mean number of counts recorded with #2 net (55 meshes/inch) was higher than f o r no net. This suggests that the attachment of a net may cause the impellor of the flow-meter to operate with less volume/revolution (lower c a l i b -r a t i o n value). 5. The percentage of water accepted by the sampler with-out a net attached while being towed at 2,k knots has been estimated as 79$ of that encountered. This estimate i s lower than the 9^$ shown by previous workers to be appropriate f o r speeds ranging from Q.75 to 1.5 knots. Apparently the tendency of the Clarke-Bumpus sampler to r e j e c t water i s enhanced considerably when the towing speed i s increased to 2.h knots. 16 TABLE I S t a t i s t i c s of the number of counts 3 obtained from f i e l d t r i a l s of Clarke-Bumpus plankton samplers MEANS FOR SAMPLERS (EACH MEAN FROM 16 OBSERVATIONS) Samper No. CB-9 CB-7 CB-6*> CB-5 CB-3 Revolutions 20*+.5 210.8 189.6 200.7 200.8 MEANS FOR MESHES (EACH MEAN FROM 16 OBSERVATIONS;) No. (Nylon) c n i l 2 10 20 Approx. meshes/inch 0 55 l¥+ 216 Revolutions 203.1 206.3 203.0 192.6 ANALYSIS OF VARIANCE Source Sum of Degrees of Mean F F Squares Freedom Square .95 .99 Samplers (S) 3826 h 956.5 5.8* 2.6 3.9 Meshes (M) 2112 3 70*+ *r .25 d 2.9 ^.3 Directions(D) 15 1 15 0.1 h.l 7.h Interactions S I M 3219 12 268 1.6 2.0 2.7 S X D 329 h 82 0.5 2.6 3.9 M X D 161 3 9+ 0.3 2.9 ^.3 S X M X D 3636 12 303 1.8 2.0 2.7 T o t a l 73^5 31 237 1.1+ 1.8 2.3 S u b t o t a l e 13298 39 E r r o r ^ 6619 ho 165.5 Totalg 19917 79 a One count equals 10 revolutions of the impellor h The f a i l u r e of the impellor to rotate f r e e l y was e a s i l y observed. Frequent cleaning and l u b r i c a t i o n of bearings helped correct t h i s f a u l t . c The meshes/inch of wire screen i n the window of the bucket terminating the net approximates that of the nylon i n the net i t s e l f . 17 d S i g n i f i c a n t e Sum of squares and degrees of freedom f o r the combined ef f e c t s of Samplers, Meshes, Directions and Interactions, * Variance independent ;of the differences i n means of Samplers, Meshes, Directions and Interactions. g Sum of squares and degrees of freedom f o r a l l observations without taking i n t o account any c l a s s i f i c a t i o n . APPENDIX I I . THE SUBS AMPLER 1 INTRODUCTION Specimens from whole samples were often too numerous to be sorted and counted e f f i c i e n t l y . A subsampler was designed to minimize this d i f f i c u l t y by withdrawing from the sample a representative 10$ of i t s contained ostracods. The sub-sampler had the disadvantage of being li m i t e d to the treatment of samples containing organisms smaller than the diameter of Its r eceiving end, but had the advantage of being able to provide a thorough mixing of the sample during withdrawal of the subsample. DESCRIPTION E s s e n t i a l l y the subsampler consisted of a glass tube and a tap-operated f i l t e r pump connected by a length of f l e x i b l e tubing f i t t e d with a squeeze-bulb and clampiFIg. 1, below). The glass tube, which served for c o l l e c t i o n of the subsample, was 1^ mm. i n diameter along Its length and 8 mm. across the end designed to receive the subsample. With the clamp open, a i r was withdrawn from the tube and the subsample collected.. With the clamp closed, a i r was neither withdrawnnor replaced, and the subsample was held within the tube by surface tension across the c o n s t r i c t i o n at the receiving end and by a vacuum 2 created by the f i l t e r pump. With the bulb squeezed, the l i t t l e a i r remaining in the system was compressed and the subsample forced out. The system required that a l l connections be air tight. USE The following procedure was found to produce the best results s 1 . A l l large organisms such as shrimps, euphausids, chaetognaths, and medusae were removed from the sample. 2 . The remaining sample was diluted with 10$ formalin-seawater to 100 ml. in a 1 5 0 ml. beaker. 3 . By a figure-eight motion of the collecting tube (Pig. 1 ) , the sample was stirred to a homogeneous mixture. h. While s t i r r i n g was continued, the opening of the collec-ting tube was placed about halfway up the sample and the but-; ton of the clamp pushed to open. 5 . The subsample was stopped at the 10 ml. mark on the collecting tube by releasing the button of the clamp. 6. The subsample was transferred to a sorting dish by compression of the bulb. 3 F i g * 1 Subsampling apparatus* The sample i s s t i r r e d by the c o l l e c t i n g tube, into which the subsample i s drawn by a vacuum} the push-button clamp serves to control the vacuum, and the bulb, t» release the subsample. 1 APPENDIX I I I . VARIABILITY DUE TO SUBSAMPLING, SAMPLING, AND POPULATION DIFFERENCES INTRODUCTION I f variations due to sampling and subsampling were kept r e l a t i v e l y small, important differences i n the d i s t r i b u t i o n of a population would be detectable as differences between samples, and between the subsamples representing these samples. Since the exploratory nature of the present study demanded only indications of general trends and major differences, and since sampling v a r i a t i o n was large, precise evaluation of sub-sampling was considered to be of l i t t l e use. To give a rough i n d i c a t i o n of the r e l a t i v e amounts of v a r i a t i o n due to sub-sampling, sampling, and population differences, some of the data at hand have been analysed and compared (Tables 1 to below). I t has been considered that v a r i a t i o n due to subsampling should be smaller than that due to sampling, and that v a r i a t i o n due to sampling should be smaller than that due to population d i f f e r e n c e s . The a b i l i t y of subsampling to d i s t i n g u i s h samples that are d i f f e r e n t has been regarded as more important than i t s being able to represent the absolute numbers of specimens con-tained i n the samples. 2 COMPARISON OF VARIATIONS Va r i a t i o n due to subsampling i s expressed i n Table 1 , where counts of specimens of each species from four r e p l i c a t e sub-samples are presented along with the means of these counts. The percentage deviations from the mean of counts averaged £ 8$ f o r Conchoecia eleeans and - 7$ f o r C. pseudohamata. Sampling v a r i a t i o n , plus the v a r i a t i o n introduced by the use of subsampling i n making estimates,, i s represented i n Table 2 as the mean of percentage deviations between paired samples c o l l e c t e d under s i m i l a r conditions. Variations estimated were £ 16$ f o r Conchoecia eleeans and - 22$ f o r C. pseudohamata. about two to three times that shown above for subsampling v a r i a t i o n . V a r i a t i o n due to population differences, plus that due to the effects of sampling and subsampling used i n making estimates, i s expressed f o r samples taken under d i s s i m i l a r conditions (Table 2 ) . Samples taken from the same depth, but at d i f f e r e n t times of the day, gave a mean percentage v a r i a t i o n of £ 31$ £ o r Conchoecia eleeans and £ 26$ f o r C. pseudohamata. Those taken from the same depth and at the same time of day, but at d i f f e r e n t times of the year, gave variations of £ $h% (day) and £ 35$ (night) f o r C. elegans, and - kk-% (night)and £ 80$ (day) f o r C. pseudohamata. These variations are roughly four to ten times those shown f o r subsampling. Thus, v a r i a t i o n due to subsampling alone may be about one-_ . .._ 3 t h i r d to one-half that due to sampling and subsampling combined, and from one-tenth to one-quarter that due to the united effects of population differences, sampling, and sub-sampling. VALIDITY OF SUBSAMPLING ESTIMATES The r e p l i c a t e subsamples i l l u s t r a t e d i n Table 1 were supposed to represent 10$ of a sample containing 178 specimens of Conehoecia elegans and 315 of C. pseudohamata. Estimates obtained by subsampling were 21.75 and 33.75 specimens (Table 1); they were 10 and 2% higher than the 17.8 and 31.5 specimens expected. Knowledge of the si g n i f i c a n c e of such deviations was not considered necessary f o r i n t e r p r e t a t i o n of the re s u l t s of this exploratory study. To determine the degree with which a subsample may represent the r e l a t i v e proportions of the various growth stages i n a sample, the percentages known to be present i n a sample were ranked i n order of magnitude and compared to ranks obtained from percentages estimated from subsamples (Table *+)• The differences between ranks for the sample and those f o r the subsamples suggest that the estimations of proportions were rather poor. Although d i s t i n c t l y d i f f e r e n t percentages (eg. f o r females of Conehoecia elegans. Table h) consistently shewed the proper rank, percentages d i f f e r i n g by smaller amounts were not w e l l represented. I t seems, therefore, that estimates of proportions from single samples are of li m i t e d value. 5 TABLE I .Variation among subsamplers Subsample Specimens Average specimens v a r i a t i o n ($) Conchoecia eleeans # 1 .2 I 21 23 l? 2h 21.75 '21.75 -21.75 21.75 -13 +10 * Mean ± 8 Conchoeci a pseudohamata ' #-! -2 I •29 3I 36 33 33.25 33.25 33.25 33.25 -13 + 5 + 8 1 Mean - t 7 6 T A B L E ' 2 Vari a t i o n between s i m i l a r samples Set #1 Set #2 July 26, 1707-1758 hrs., Stat i o n 9, Net of mesh space O.H-0 mm* July 26, 1625-1712 hrs., Stat i o n 9> Net of mesh space O.H-0 mm. Depth Cm) Concentration Set #1 ( Concentration Set #2 Vari a t i o n C O eleeans 90 120 150 180 0.90 O.kl 1.00 0.30 Q.95 0.30 6.70 0.70 ± 3 16 18 ko Mean = 16 C. pseudohamata 90 120 150 180 0.90 2.30 3.50 1.80 9.95 p . 90 2.k0 1.20 t 3 kk 19 13 1 Mean " 22 7 •TABLE 3 Variati o n among d i s s i m i l a r samples C. elegans c. pseudohamata Month Night Day Va r i a t i o n 00 Night Day V a r i a t i o n Jan 0.51 0.4-3 t 8 0.38 0.06 t 73 Mar 0.4-8 0.00 100 0.4-8 0.00 100 "May- 0.38 0.5^ 17 1.35 2.08 21 July 0.4-3 0.4-9 15 0.80 0.44 34-Sep 0.21 0.4-4- 35 0.66 1.20 29 Nov 1.02 0.39 4-5 1.53 1.29 9 Var i a t i o n influenced hy the time of day Mean 3 ;: 3 i Mean 26 Vari a t i o n influenced by the time of year: Means" 135 +34- ±44 t80 TABLE Vi-v a r i a t i o n i n the r e l a t i v e proportions of various growth stages, due to subsampling Species Conehoecia eleeans C. pseudohamata Stage 3 2 j* $ 4- 3 2 j&* % Sample Percenta Rank *e 6 14- 22 58 1 2 3 ^ 16 31 17 11 25 2 5 3 1 ^ Subsample #1 #2 #3 #4-1 3 2 4-1 2£ 2£ 4-lk lk 3 C4-1 2 3 M-2 4 - 3 1 5 2k 5 2k 1 4-2k 5 1 2k 4-4 - 5 2 1 3 

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