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A Lower Cambrian trilobite fauna from near Cranbrook, B.C. 1952

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A LOWER CAMBRIAN TRILOBITE FAUNA " F R O M NEAR" CRANBROOK, B . C . by RAYMOND VICTOR BEST A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department of GEOLOGY AND GEOGRAPHY We accept t h i s t h e s i s as conforming to the standard r e q u i r e d of candidates f o r the degree of MASTER OF APPLIED SCIENCE. fii > /f 7 Members of the Department of GEOLOGY AND GEOGRAPHY THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1952 ABSTRACT T r i l o b i t e s t y p i c a l of the well known Olenellus zone of the Lower Cambrian constitute a large c o l l e c t i o n from the Eager Formation, near Cranbrook, B.C. Their c l a s s i f i c a t i o n i s discussed, and two new snecies described:: Olenellus eagerenals n.sp. and Olenellus s c h o f i e l d l r&spjV Since the use of c e r t a i n structures i n c l a s s i f y i n g o l e n e l l i d s has been disputed i n the past, these and other less controversial features are c r i t i c a l l y examined, insofar as they apply to the genera and species present. From th i s study the writer assembles c r i t e r i a which might be used by l a t e r workers to r e - define the generic and s p e c i f i c positions of selected species of Olenellus and Faedeumias^ TABLE OP CONTENTS ABSTRACT i INTRODUCTION • — 11 Acknowledgements • - - - i v Chapter I_ CRANBROOK AREA H i s t o r i c a l Summary — • 1 Strat igraphy — • — 3 L i t h o l o g y of the O l e n e l l u s Zone r 4 Chapter I I TAXONOMIG.. CONSIDERATIONS - I n t r o d u c t i o n — — — • 6 Terminology — — • — — — . . — 7 Terminal Segments — •— 7 F a c i a l Sutures • — .-- 9 Cephalic Spines ; — — — ;. — 12 F r o n t a l Lobe and Brim -—— • : - — 13 Hypostoma and Epistomal P l a t e — 15 Thorax : - — — . — • .17 Post-Ocular Nodes -•- 19 Ornamentation • — — 20 Growth Stages • — — • 21 P r e s e r v a t i o n — • ••— 23 Cephalic and Thoracic R a t i o s — • 26 Systematic P o s i t i o n of O l e n e l l i d s = 27 Generic and S p e c i f i c D i s t i n c t i o n s --— 28 Recommendations f o r F u r t h e r Study • 30 Chapter I I I DESCRIPTION OF GENERA AND SPECIES Q l e n e i l u s —• — < — • 31 O l e n e l l u s .of., g i l b e r t ! 35 O l e n e l l u s ea^erenaIs. n . sp> •-• 37 -Olenellus. . .sohofieldl . n . s p . .— •— 40 « Paedeumias • • • 42 Paedeumias nevadensis -—-•—-—• 44 Wanner i a T - : ? . 45 Wanner l a walcottana - r — 47 Bonnla ? — .- 49 Bonnla e-f-. Qolumbensls 50 BIBLIOGRAPHY - EXPLANATION OF PLATES 52 56 ILLUSTRATIONS — • Olenellus g l l b e r t l — • Frontispiece Table I Cephalic and Thoracic Ratios 27 Table II Possible Generic D i s t i n c t i o n s 29 Plate I Olenellus eagerensis ri» sp« and Olenellus s c h o f i e l d i . n. sp> - Facing Page — 56 Plate II Paedeumias nevadensls. Olenellus of. g i l b e r t i . Wanneria walcottana and Bonnla c f . columbensis". Facing Page 57  l i . A LOWER CAMBRIAN TRILOBITE FAUNA "FROM NEAR. CRANBROOK,'B.C.*. INTRODUCTION The f o l l o w i n g study i s based upon a c o l l e c t i o n of t r i l o b i t e s , made l a r g e l y by Mr. C. G a r r e t t , l a t e of Granbrook, B . C . , and bought by the U n i v e r s i t y of B r i t i s h Columbia. The c o l l e c t i o n was taken from two l o c a l i t i e s of d i f f e r i n g l i t h o - logy w i t h i n the Eager Formation. I t c o n s i s t s almost e n t i r e l y of t r i l o b i t e s t y p i c a l of the w e l l known O l e n e l l u s zone, which define the age of the rocks i n which they were found as Lower Cambrian. I t may be that conclusions based on observations of fauna from a s i n g l e l o c a l i t y should be r e s t r i c t e d to that p a r t i c u l a r a r e a . A student faced w i t h . o n l y one phase of a l a r g e r problem may be-tempted to extrapolate unreasonably. Many g e n e r a l i z a t i o n s can be quoted from the l i t e r a t u r e analogous to those of the three b l i n d men d e s c r i b i n g an elephant. But i n the wider f i e l d of p a l e o n t o l o g i - c a l r e s e a r c h a clue to one of the l a r g e r problems may l i e at some s i n g l e l o c a l i t y , p r o v i d i n g confirma- t i o n of a t e n t a t i v e hypothesis or the r e f u t a t i o n of an accepted p r i n c i p l e . i l l The w r i t e r r e g r e t s the l a c k of time to continue the study of t h i s e x c e l l e n t c o l l e c t i o n . I t i s almost c e r t a i n that only a few of the l e g i t i m a t e species have been r e c o g n i z e d . A great d e a l more could be learned of the ontogenies, and p o s s i b l y of s p e c i f i c and generic r e l a t i o n s h i p s , of the o l e n e l l i d s , from the scores of Immature specimens. No doubt t o o , a d d i t i o n a l m a t e r i a l c o l l e c t e d by p a l a e o n t o l o g i s t s conversant w i t h the outstanding problems would provide much v a l u a b l e information from the s t r a t i g r a p h l c and e c o l o g i c a l p o i n t s of view. In s p i t e of the l i m i t a t i o n s of time and experience, i t i s hoped that the observations made here w i l l be of some value i n f u r t h e r s t u d i e s of the o l e n e l l i d s as a whole 8 i t : ACKNOWLEDGEMENTS The w r i t e r g r a t e f u l l y acknowledges the guidance and c o n s t r u c t i v e c r i t i c i s m of Dr. V . J e O k u l i t c h i n the p r e p a r a t i o n of t h i s t h e s i s , and Invaluable a s s i s t a n c e i n photograph- i n g specimens. To Dr. M.Y« Will iams s p e c i a l thanks are due f o r p r o v i d i n g much general, i n f o r m a t i o n , but p a r t i c u l a r l y f o r the l o a n of h i s p e r s o n a l , c o l l e c t i o n of o l e n e l l i d t r i l o b i t e s . Mr. W. Armstrong and Mr. J . F i s h e r of the Department of Mining and Metal lurgy k i n d l y encouraged and a s s i s t e d i n experimental attempts at micro-photography. 1. CHAPTER I CRANBROOK AREA H i s t o r i c a l Summary The f i r s t extensive g e o l o g i c a l work i n the Granbrook Area-was c a r r i e d out by s c h o f i e l d (1915, 1922). P r i o r to h i s 1915 memoir b r i e f reconnaissances had been made by Dawson (1895) and McEvoy (1899). The most recent r e v i s i o n of s t r a t i g r a p h y near Granbrook was com- p l e t e d by Rice (1937, 1941) a copy of whose 1937 map Is i n c l u d e d i n the present paper. The presence of the O l e n e l l u s zone was f i r s t r e p o r t e d between Granbrook and Port Steele by S c h o f i e l d (1922). The f o s s i l s he c o l l e c t e d were sent to C D . Waleott, who I d e n t i f i e d the f o l l o w i n g t r i l o b i t e s : G a l l a v l a o f . nevadensis Waleott Wannerla n . sp ? Mesonaois g i l b e r t i Meek Wannerla o f . waloottanus (Wanner) O l e n e l l u s c f . fremontl Waleott Prototypus seneotus B i l l i n g s Waleott i s quoted concerning t h i s c o l l e c t i o n as s a y i n g : "This fauna belongs to the upper p a r t of the Lower Cambrian and i t i s e s s e n t i a l l y the same as that found above the tunnel at Mt. Stephen, B . C . , and i s a l s o 1. Dates i n parentheses r e f e r to the B i b l i o g r a p h y i n the back of the r e p o r t . 2. found more or l e s s a l l along the c o r d i l l e r a n system down into southern Nevada." (Ibid, p 12) The species found by Rice (1937) apparently did not d i f f e r to any great extent, since no further faunal information i s embodied i n hi s report. Although professional geologists were mainly interested i n the Cranbrook.Area.from an economic point of view, at le a s t two amateurs became very keen f o s s i l hunters. Col. Pullen and C. Garrett made exten- sive c o l l e c t i o n s of t r i l o b i t e s and other f o s s i l s from two l o c a l i t i e s , one on the main Cranbrook-Fort Steele road, the second just east of St. Eugene Mission. In this, second l o c a l i t y they put i n a small a d i t i n grey shale and were rewarded.by obtaining a very f i n e c o l l e c t i o n , including•numerous examples of the young growth-stages of Olenellus, Paedeumias and Wanneria. Unfortunately, c e r t a i n l o c a l inhabitants, suspecting that such incomprehensible actions were con- nected with something more remunerative than a " t r i l o - b i t e mine", staked out claims. C o l l e c t i n g had to be" d i s - continued and the adit f i l l e d i n . Dr. M.Y. Williams of the University of B r i t i s h Columbia made a f a i r l y extensive c o l l e c t i o n from both l o c a l i t i e s i n 1954, The Garrett c o l l e c t i o n , obtained l a t e r by the University, together with that of Dr. Williams, t o t a l s some fourteen hundred specimens, and furnishes the material for t h i s study. STRATIGRAPHY The presence of Bonnla and Olenellus i n the Eager Formation places the age of these rocks i n the upper part of the Lower Cambrian (Rasetti, 1951)• The Eager a r g i l l i t e s , some thousands of feet thick, are underlain by the Granbrook Formation, which Is 600 feet thick. The contact between these two i s believed by Rice (1941) to be gradational. The Cranbrook Formation consists largely of quartzite, pebble conglomerate, and some magnesite; although f o s s i l s are absent, i t s age i s also assigned to the Lower Cambrian. The Cranbrook rests uneonformably on Proterozoic rocks of Upper P u r c e l l Age. The age relationships of the Lower Cambrian Olenellus zone have recently been studied by Rasetti (1951)• Tentatively the Eager Formation may be cor- related with Peyto limestone, that i s , the top of the Lower Cambrian St. Piran sandstone at Kicking Horse Pass. I t i s also correlated with the lower part of the Burton Formation at Elko (Schofield, 1922). 4 LITHOLOGY OF THE OLENELLUS ZONE I t i s stated by Resser and Howell (1938, p. 207) that: "The l i t h o l o g i c s i m i l a r i t y of Lower Cambrian s t r a t a i n a l l parts of the world i s astonishing, and t h i s s i m i l a r i t y i s p a r t i c u l a r l y .noticeable i n the shales bearing o l e n e l l i d t r i l o b i t e s . For ... , the most part, these rocks are clay shales, i n .r many places calcareous, but everywhere f i n e grained; the Joint surfaces are almost u n i v e r s a l l y stained with limonite generally i n d e n d r i t i c form. Moreover there was s u f f i c i e n t calcareous content i n the o r i g i n a l muds to prevent many tests from being completely fl a t t e n e d . " The Eager Formation i s no exception to t h i s statement. According to Rice (1937, p. 21) "The bulk of the formation consists of dark grey, often rusty-weathering a r g i l l i t e ... Blue- grey, o l i v e green, and. reddish platy a r g l l l i t e s also occur i n places. They are a l l soft, e a s i l y deformed rocks and are everywhere f o l i a t e d . The formation i s not generally limy, but beds' of calcareous a r g i l l i t e may occur i n any part of i t ..." It i s apparent from the foregoing statements that the Olenellus zone i s p e c u l i a r to a somewhat r e s - t r i c t e d type of l i t h o l o g y . But within the zone i t s e l f , i n t h i s case the Eager Formation, c e r t a i n p e c u l i a r i t i e s of faunal d i s t r i b u t i o n are s u p e r f i c i a l l y apparent. The t r i l o b i t e s were c o l l e c t e d from two l o c a - l i t i e s named here A and B. At l o c a l i t y A# °*i t l i e main Cranbrook-Fort Steele road (see map i n back cover) the rocks are sof t l i m o n l t i c a r g l l l i t e s ; at B, just south 5. of St. Mary River and east of St. Eugene Mission, they consist of harder, dark grey, rusty-weathering, dolomitic, sometimes sandy a r g i l l i t e s . At both - l o c a l i t i e s the dominant forms are Olenellus ef . g i l b e r t l and Paedeumias nevadensls; but at B, not only Is the proportion of 0. eagerensls higher, but here were found the only spec imens r e f e r r e d to 0. s c h o f i e l d l and to Bonnia c f . columbensls'. Since the writer d i d not carry out the c o l - l e c t i n g himself, numbers of imperfect or incomplete specimens may have been abandoned, with consequent "weighting" of the proportions of species c o l l e c t e d . Furthermore, the stratigraphic r e l a t i o n s h i p of the two outcrops i s not known,, so that i t i s possible that e n t i r e l y d i f f e r e n t ages within the Olenellus zone are represented". Although no p o s i t i v e conclusion may be drawn from these observations of faunal d i s t r i b u t i o n , the f a c t s do not, at least, contradict the suggestion made by Rasetti (1951, P 82)s "The Olenellus zone may represent a shaly f a d e s of the Lower Cambrian deposits rather than a d e f i n i t e time i n t e r v a l . In northwestern Vermont, f o r example, olenellids.seem to p r e v a i l when the Lower Cambrian i s represented by s i l i c i o u s . s h a l e s , while Bonnla and small ptychoparid t r i l o b i t e s are dominant i n limestone or dolomitic formations, regardless of age.'1 _ CHAPTER I I TAXONOMIC CONSIDERATIONS I n t r o d u c t i o n Probably no group of t r i l o b i t e s has aroused more controversy and d i s c u s s i o n than the o l e n e l l i d s . They are unique i n many ways. But f o r years t h e i r p e c u l i a r i t y was not recognized, and the greatest e f f o r t s were made to f i t them i n t o e s t a b l i s h e d schemes of c l a s s i f i c a t i o n , . Much of the t r o u b l e stemmed from the o l d e r conceptions of e v o l u t i o n . A l a t e r form, showing s u p e r f i c i a l resemblance to another-, l i v i n g perhaps m i l l i o n s of years e a r l i e r , was considered to be neces- s a r i l y on the d i r e c t l i n e of descent. Homologizlng of p a r t s was s t i l l a new idea i n the l a s t century, of great s c i e n t i f i c v a l u e , but c a r r i e d to extremes-. Some traces of these abuses have l i n g e r e d on to the present day. The controversy a r i s i n g i n the study of o l e n e l l i d s was concerned mainly with the development and o r i g i n of two or three features of the carapace: t e r m i n a l segments, c e p h a l i c sutures, and to a l e s s e r extent, c e p h a l i c s p i n e s . Since an attempt i s made i n t h i s paper to augment e s t a b l i s h e d c r i t e r i a f o r d i s t i n - g u i s h i n g the s h i e l d s of c e r t a i n t r i l o b i t e s , the above features and some others of a l e s s c o n t r o v e r s i a l nature are discussed i n s o f a r as they apply to the genera and 7. species examined. Furthermore, although the genus Mesonacls has heen d e c l a r e d i n v a l i d (Resser and Howell 1938), i t i s p o s s i b l e that at some future time enough data w i l l have been compiled to permit the r e l n t r o - d u c t i o n of t h i s c o n t r o v e r s i a l name. With t h i s i n mind the w r i t e r i n d i c a t e s p o s s i b l e c r i t e r i a f o r a r e d e f i n i t i o n of "Mesonacls" ( B . B . ) ' . TERMINOLOGY The terminology used throughout t h i s paper i s e s s e n t i a l l y that of Howell et a l * (1947) with some of the modif icat ions suggested by Ross (1948) and adopted by R a s e t t i (1951)• Since i t i s suggested that the a n t e r i o r of the cephalon of o l e n e l l i d s i s not separable i n t o f i x e d and free cheeks, the "brim" Is r e s t r i c t e d i n t h i s paper to mean that p a r t of the c e p h a l i c surface at the c e n t r e , l y i n g between the f r o n t a l lobe and the r i m * To avoid tedious r e p e t i t i o n , the a x i a l spine on the 15 t h o r a c i c segment i s o c c a s i o n a l l y r e f e r r e d to as "the 1 5 t h s p i n e " , even when other spines are not present on segments a n t e r i o r t o the 1 5 t h * TERMINAL SEGMENTS The rudimentary p o s t e r i o r segments of o l e n e l l i d s are only r a r e l y observed. Under c o n d i t i o n s of almost 8. p e r f e c t p r e s e r v a t i o n they may be concealed by the massive a x i a l spine on the 15th segment, o r perhaps - f o l d e d forward under the t h o r a x . In most specimens, since these segments were probably very f r a g i l e , they seem to have been l o s t e n t i r e l y . For many years G.D. Walcott was an i n f l u e n - t i a l proponent of the theory that the 15th spine on O l e n e l l u s was a t e l s o n , l i k e that on Limulus, the modem k i n g c r a b . The presence of t e r m i n a l segments and small p y g i d i a i n a l l other o l e n e l l i d genera decided him to set up Mesonaols r a t h e r than O l e n e l l u s as the type-genus of the family Mesonacldaev The genotype, M. vermontana. was known to possess ten rudimentary segments, and a small pygidium, p o s t e r i o r to the s p i n e - b e a r i n g 15th t h o r a c i c segment. During the course of time, more and more specimens r e p r e s e n t i n g e s t a b l i s h e d species of O l e n e l l u s were found to possess rudimentary segments, n e c e s s i t a t i n g t h e i r t r a n s f e r , by Walcott and h i s f o l l o w e r s , to Mesonacis or Paedeumias, the nearest r e l a t e d genera known to possess such f e a t u r e s . Resser (1928) a f t e r showing c o n c l u s i v e l y that O l e n e l l u s d i d Indeed possess rudimentary segments, pointed out that d i f f e r e n c e s i n these could be detected 9. at the generic l e v e l ; those, of Mesonacls had d e f i n i t e , grooved pleurae, those of Olenellus had ungrooved pleurae, out those of Paedeumias lacked pleurae altogether. In 1938, Resser and Howell, i n r e v i s i n g the genus Olenellus established the f a c t that i t s posterior segments did not necessarily possess pleurae. Generic redescription included c e r t a i n other c h a r a c t e r i s t i c s , so as to Include forms formerly named Mesonacls. Thus, the names Mesonacls and Mesonacidae were dropped. Observations With the exception of Wannerla walcottana. -the specimens i n the c o l l e c t i o n , although well preserved, generally exhibit neither the posterior rudimentary segments nor the. pygidlum. In nearly every complete thorax of Olenellus and Paedeumias the 1 5 t h spine i s extremely heavy, i t s base extending f u l l y across the a x i a l lobe, and tapering f a i r l y slowly, so that i t e f f e c t i v e l y conceals whatever l i e s beneath. One speci- men of Olenellus c f . a l l b e r t i has no les s than three very poorly preserved segments posterior to the spine-bearing 1 5 t h , but no pygidium has been observed. FACIAL SUTURES The c l a s s i f i c a t i o n of t r l l o b i t e s i s l a r g e l y based upon the development and p o s i t i o n of the f a c i a l 10'. suture, or l i n e of Junction of the f i x e d and f r e e cheeks of the cephalon. I t i s g e n e r a l l y assumed that t h i s was.the l i n e along which the t r i l o b i t e cephalon s p l i t during e c d y s i s , the p e r i o d i c moulting common to a l l Crustacea. I t i s p o s s i b l e that the sutures of t r i l o b i t e s are not i n v a r i a b l y homologous. According t o S t u b b l e f i e l d (1936, p 410): "It cannot be denied t h a t the presence of cephalic sutures f a c i l i t a t e d e c d y s i s , but i t i s at l e a s t arguable that the sutures e x i s t e d only f o r t h i s purpose.?' The o l e n e l l i d s have long been a source of d i f f i c u l t y i n taxonomy, since they do not appear to possess these u s e f u l s t r u c t u r e s i n f u n c t i o n a l form, I . e . as a means of f a c i l i t a t i n g ecdysisv Observa- t i o n s , made of specimens since the f i r s t d e s c r i p t i o n of O l e n e l l u s ( H a l l , 1859) have been v a r i o u s l y i n t e r - p r e t e d . A complete h i s t o r y of the disputes over the f a c i a l sutures i n o l e n e l l i d s i s g iven by Raw (1937) and S t u b b l e f i e l d (1936). B r i e f l y , the main opinions concerning f a c i a l sutures and t h e i r s i g n i f i c a n c e may be summarized: r. Rudimentary - i n process of o r i g i n or s y n t h e s i s . ( I b i d ) . 2. V e s t i g i a l - or i n a c o n d i t i o n of symphysis. (Raw, 1937). 11. Observations In examining nearly 500 complete cephala of Olenellus and Paedeumias.the writer has made a number of observations: 1. The tendency f o r the cephalon to break i n c e r t a i n places i s indisputable. The l i n e s of ant e r o - l a t e r a l fracture, interpreted by B e l l (1931) and others as f a c i a l sutures,have c e r t a i n c h a r a c t e r i s t i c s . (a) They are seldom symmetrically developed. (b) Ho two cephala have been found with the fractures i d e n t i c a l . (c) They are no more frequent i n occurrence than the lo n g i t u d i n a l l i n e of fracture down the approximate centre of the g l a b e l l a . (d) Unbroken cephala show no l i n e , r a i s e d or depressed, suggestive of an inherited l i n e of weakness i n t h i s d i r e c t i o n . I t i s suggested, therefore, that these fractures are e n t i r e l y mechanical i n o r i g i n , (see Preservation) 2. The pos t e r o - l a t e r a l r a i s e d l i n e running from under the eye toward the genal angle i s as often as not asymmetrically developed. Fre- quently, t h i s l i n e separates into two or more branches indistinguishable from the venation referre d to by Lockman (1947, p. 61). Fracture p r a c t i c a l l y never occurs along or p a r a l l e l to t h i s l i n e . I t appears that i f t h i s p o s t e r o - l a t e r a l l i n e has s t r u c t u r a l significance i t i s not part of a v e s t i g i a l f a c i a l suture, nor, i n i t s present form, does i t appear to be a rudimentary suture i n the process of o r i g i n . 3» The intra-marginal sutures described by Resser (1928) i n Olenellus fremonti are c l e a r l y exhi- b i t e d i n t h i s c o l l e c t i o n i n the wider-rimmed specimens of Olenellus and Paedeumias, but even more s t r i k i n g l y i n the young stages of Wannerla walcottana. 12.. CEPHALIC SPINES In t h e i r e a r l i e s t l a r v a l stages o l e n e l l i d s may develop three p a i r s of c e p h a l i c s p i n e s . Gf these, the genal spines are r e t a i n e d as a prominent feature i n a d u l t s of a l l genera; the i n t e r g e n a l spines are often l o s t during development; the a n t e r o - l a t e r a l s p i n e s , with the one exception of O l e n e l l o i d e s a r e . i f present at a l l , r e s t r i c t e d e n t i r e l y to the-youngest i n d i v i d u a l s . I t was suggested "by Walcott (1910, p . 237) and has "been s t r o n g l y maintained by Raw (1937* p» 579) that the c e p h a l i c spines i n o l e n e l l i d s are segmental i n o r i g i n . As S t u b b l e f i e l d p o i n t s out (1936, p. 425) there seems to be l i t t l e j u s t i f i c a t i o n f o r t h i s view. Since the i n t e r g e n a l spines i n O l e n e l l u s and Paedeumias appear to stem from the p r e - o c e i p i t a l g l a b e l l a r lobe and not, as Raw s t a t e d , from the o c c i p i t a l , much of h i s i n t e r p r e - t a t i o n i s rendered i n v a l i d . There seems to be l i t t l e doubt that the r e t e n t i o n of cephalic spines Is a p r i m i t i v e c h a r a c t e r i s t i c . But whatever t h e i r f u n c t i o n , i f any (Raymond 1928, p. 168) they are taxonomically u s e f u l * Observations No a n t e r o - l a t e r a l spines such as described by Walcott have been i d e n t i f i e d i n any of the l a r v a l o l e n e l l i d s 13. In the c o l l e c t i o n , down to the smallest cephalon, 1.25 mm In width, of Paedeumias. Intergenal spines are more s t r o n g l y developed than the genals i n cephala: l e s s than 5 mm. wide of 0'. c f g i l b e r t ! and P. nevadensis, but g r a d u a l l y reduce i n comparative s i z e d u r i n g growth. The i n t e r g e n a l spines In these species are u s u a l l y l o s t when the cephalon i s about 15 mm. i n w i d t h . In almost a l l specimens possessing Intergenal s p i n e s , a r i d g e connects the spine almost d i r e c t l y across the cheek-to-the r e a r of the p o s t - o c u l a r node,, opposite the o c c i p i t a l furrow. FRONTAL LOBE AND BRIM The a n t e r i o r g l a b e l l a r lobe of o l e n e l l i d s i s u s u a l l y d i s t i n c t l y developed. I t s distance from the r i m , i t s s i z e r e l a t i v e both to the succeeding lobes and to the whole cephalon, and i t s convexity, have a l l been used as a i d s i n c l a s s i f i c a t i o n . The r e l a t i v e s i z e of the a n t e r i o r lobe to a large extent governs the shape and taper of the g l a b e l l a ' . The s e p a r a t i o n of r i m from g l a b e l l a by a brim possessing an a x i a l r i d g e i s d i a g - n o s t i c of Paedeumias; the r i d g e i s p o s s i b l y due to " . . . c o m p r e s s i o n of the t e s t onto the hypostoma s t a l k during f o s s i l i z a t i o n . " (Resser and Howell 1938 p . 225) 14. Convexity i s i t s e l f a r e l a t i v e quantity, most e a s i l y estimated i n terms of the abruptness of the r i s e of the anterior lobe from i t s own f r o n t a l margin. Observations One of the most s t r i k i n g features of the cephalon of Olenelliis eap;erensis at a l l growth stages examined i s the extremely abrupt r i s e of the f r o n t a l lobe from the narrow rim. The f r o n t a l lobe of 0. c f . g i l b e r t i i s pre- ceded by a brim and rim of approximately equal width. Between 0. cf. g i l b e r t 1 and P. nevadensis many t r a n s i t i o n a l forms have been observed, with the width of the brim varying from one to three times that of the rim. The rim i t s e l f v a r i e s i n width between specimens otherwise i d e n t i c a l ; specimen M.YJ. i s t y p i c a l of 0. c f . g i l b e r t ! except for i t s broad rim (Pi.IE P i g . 8 ) • The growth stages of 0. c f . g i l b e r t ! and P. nevadensis le s s than 8-10 mm. i n width are i n d i s t i n - guishable; the brim i s wide i n a l l cephala examined, and i n the better preserved specimens possesses the t y p i c a l Paedeumias ridge. Consequently, a l l minute forms of these two species are together referr e d to "Paedeumias" i n t h i s paper. 15: HYPOSTOMA AND EPISTOMAL PLATE The hypostoma, I f w e l l preserved, may be a valuable a i d i n I d e n t i f i c a t i o n of o l e n e l l i d s : . As i n most t r i l o b i t e s , i t i s a l i p - l i k e s t r u c t u r e f i t t i n g convex down beneath the a n t e r i o r - g l a b e l l a r lobe;. The hypostomae of Wannerla and Paedeumias from the type l o c a l i t i e s are equipped with d e n t i c u l a t e p o s t e r i o r margins; i t i s b e l i e v e d (Waleott, 1910, p . 328) that O l e n e l l u s g i l b e r t l possessed the same feature 1 * In O l e n e l l u s and Paedeumias the hypostoma i s attached to the epistomal p l a t e , which i s i n t u r n apparently connected a n t e r i o r l y to the doublure, the two together occupying the width of the r i m at the axis'. The most important diagnostic feature of Paedeumias i s t h e " s t a l k e d attachment of the hypostoma to the epistomal p l a t e , often i n d i c a t e d d o r s a l l y by a narrow a x i a l r i d g e across the b r i m . I f the epistomal p l a t e of a l l members of O l e n e l l u s and Paedeumias l i e s d i r e c t l y under the r i m , and the hypostoma no f u r t h e r forward than under the f r o n t a l g l a b e l l a r l o b e , s ince the two must be attached, three condit ions can govern the mechanics of attachment. I f the r i m Is adjacent to the f r o n t a l lobe the hypostoma and epistomal p l a t e may be attached d i r e c t l y ; I f the distance between f r o n t a l lobe and rim. i s i n c r e a s e d , / 16. e i t h e r the p l a t e and rim must be p r o p o r t i o n a t e l y wider f o r d i r e c t attachment, o r , i f the p l a t e remains narrow a s t a l k e d attachment must develop. Concerning Paedeumias, Resser and Howell (1938, p . 226) s t a t e : "The hypostoma i s attached to the m a r g i n a l , or more l i k e l y , epistomal p l a t e , by a s t a l k whose l e n g t h equals the distance from the g l a b e l l a to the r i m . " Observations The epistomal p l a t e s of 0. eagerensls and 0. s c h o f i e l d l have not been observed w i t h any c e r t a i n t y . That of w. waleottana i s s l i g h t l y narrower than the r i m , with hypostoma i n d i r e c t connection. D e n t i c u l a t i o n has been observed on only one hypostoma a s s o c i a t e d with a s m a l l Paedeumias. No s e r r a t i o n s or t e e t h have been seen, on any hypostomae of Wanner la, wale ot tana, although the epistomal p l a t e of t h i s t r i l o b i t e i s as prominently d e n t i c u l a t e as that of the h o l o t y p e . Two very p e r f e c t s h i e l d s of O l e n e l l u s of g i l b e r t ! , although l a c k i n g the hypostoma, r e t a i n the epistomal p l a t e s l i g h t l y drawn back from the r i m . H a l f - way from the genal angle to the centre the p l a t e i s about h a l f the width of the r i m , widening to one r i m - width at the a x i s . . At t h i s p o i n t a narrow s e c t i o n of the p l a t e i s missing (see F r o n t i s p i e c e ) . The brim here i s about twice the width of the r i m . On a second specimen I T . the. p l a t e Is unbroken, and a widened p o r t i o n at the a x i s i s s l i g h t l y longer than the missing p a r t i n the f i r s t . I f the o r i g i n a l p o s i t i o n of the p l a t e was d i r e c t l y under the r i m , and the widened or missing p a r t represents the attachment of the hypostoma, such attachment must have been narrower than l o n g , i n other words a s t a l k . This inference cannot be confirmed at present,^ since no s t a l k has been d i r e c t l y observed?. The epistomal p l a t e of o l e n e l l i d s seems to have been hooked or anchored i n some way at the p o s t e r i o r ends, jU3t i n s i d e the genal a n g l e . F l a t t e n i n g of the cephalon d u r i n g f o s s i l i z a t l o n would p u l l the ends a p a r t , g i v i n g r i s e to the observed drawing back of the p l a t e from i t s o r i g i n a l p o s i t i o n at the r i m . THORAX In most o l e n e l l i d s the a x i a l spine of the 15th t h o r a c i c segment i s very large'. But the o v e r a l l aspect of the thorax of O l e n e l l u s and p a r t i c u l a r l y of Paedeumias i s dominated by the extreme enlargement of the t h i r d p l e u r a l segments, extending i n t o s lender spines 1 . The shape of the thorax, ' "wide" or "narrow" of authors, i s compounded of s e v e r a l v a r i a b l e s : width of a x i a l and of p l e u r a l l o b e s , r e l a t i v e both to each 13 other and to t h e i r length, and to a c e r t a i n extent the degree of l a t e r a l or l o n g i t u d i n a l compression and f l a t t e n i n g subsequent to b u r i a l . The main, central parts of the carapace were r i g i d and more or less b r i t t l e , even when the t r i l o b i t e was a l i v e , but i t i s probable that the f a l c a t e t i p s of the pleurae were less so. Consequently, the degree of flexure of these t i p s , either before or a f t e r b u r i a l , i s d l a g n o s t i c a l l y of l i t t l e value. But the sharp or gradual angling back of pleurae at a point proximal from the outer t i p of the p l e u r a l groove may frequently a i d In dist i n g u i s h i n g specimens. For instance, the pleurae of Q« eagerensis usually angle back sharply, whereas those of Paedeumias and most species of Olenellus tend to swing back more gradually. In some species the r e l a t i v e length of p l e u r a l groove to f a l c a t e t i p reduces uniformly from front to back, as i n W. waleottana (Wanner, 1901, p. 267). In t h i s species, where the t i p s are not unduly extended into spines, the r a t i o may be used as an i n d i c a t i o n of the "number" of segment from which an i s o l a t e d complete pleuron might have come, permitting a rough estimate to be made of the size of o r i g i n a l s h i e l d . But the r e l a t i v e length of a selected p l e u r a l groove may also be compared between species as a i 9 ; d i a g n o s t i c a i d . I f the second p l e u r o n , which i s f r e - quently preserved and e a s i l y i d e n t i f i a b l e , i s examined, the r a t i o of l e n g t h of p l e u r a l groove to width of a x i a l lobe i s reasonably constant f o r a p a r t i c u l a r s p e c i e s , •This r a t i o i s i n the order of 5:4 i n Paedeumias and i n most species of O l e n e l l u s , but only about 3:4 i n 0'. eagerensis . POST-OCULAR NODES P o s t - o c u l a r nodes i n o l e n e l l i d s have been b r i e f l y r e f e r r e d to by a number of authors,, They are smooth mounds, u s u a l l y e l l i p t i c a l , " . . . o n the f i x e d cheeks back o f , and i n s i d e o f , the eyes" (Resser and Howell , 1938, pm 225) :« On O l e n e l l u s and Paedeumias they seem to be best developed i n those species whose p a l p e b r a l lobes are some distance from the p o s t e r i o r c e p h a l i c margin. On 0 . s c h o f l e l d i the p o s t - o c u l a r nodes are p a r t i c u l a r l y prominent, evenly s l o p i n g up and back from the Junction of the d o r s a l and p a l p e b r a l furrows to maximum e l e v a t i o n opposite the r e a r of the 3 r d g l a b e l l a r lobe|. At t h i s p o i n t they drop away s t e e p l y to disappear opposite the o c c i p i t a l furrow. 0 . eagerensis , on the other hand, possesses long narrow p o s t - o c u l a r mounds of f a i r l y even height- ( P l . I Fig.4) extending along the s ide of the d o r s a l furrow from i n s i d e the p a l p e b r a l lobe to j u s t back of the o c c i p i t a l furrow'. 20 At t h i s stage i n the research, no function may d e f i n i t e l y be assigned to post-ocular nodes or mounds. But i t seems reasonable to assume that they have some anatomical explanation. As a f i r s t working hypothesis i t i s suggested that they represent the ven t r a l "housing" f o r paired organs, possibly ovaries, perhaps digestive glands, or both. I f they are ultimately proven to r e f l e c t i n t e r n a l anatomy they may well be of greater taxonomic value than has hitherto been thought. ORNAMENTATION Surface ornamentation i s not an important c h a r a c t e r i s t i c g e n e t i c a l l y , but c e r t a i n species may exhibit unique markings which are diagnostic'. Thus, by means of the r e t i c u l a t e surface ornamentation "even a small fragment can be assigned to Wannerla" (Resser and Howell, 1938, p. 246). This type of polygonal pattern has been observed on the dorsal surface of a l l the larger specimens of W. walcottana i n the c o l l e c t i o n . The cheek surface of Olenellus s c h o f l e l d l i s unlike that of any other form i n the c o l l e c t i o n , but consists of a pattern of r a d i a t i n g , i r r e g u l a r l y inoscula- t i n g , raised l i n e s , reminiscent of the v e i n pattern of a l e a f . According to Lochman (1947, p« 61) t h i s venation i s neither ornamentation nor diagnostic; 21 "... but rather i t appears to be the Impress of an i n t e r n a l anatomical structure on the carapace. As i t has been observed i n many apparently unrelated genera ranging through the Paleozoic, It i s considered to be a feature c h a r a c t e r i s t i c of the whole c l a s s . " Ornamentation such as that figured by Waleott (1910) on 0. g i l b e r t l has not been observed on any specimens here. However one incomplete cephalon of 0 :. ef... g i l b e r t l exhibits an i r r e g u l a r r a i s e d f e r r u - ginous network of a d i f f e r e n t kind. Although the writer thinks that t h i s has an inorganic explanation, that of d e n d r i t i c p r e c i p i t a t i o n i n a narrow f i s s u r e , i t s development may have been determined by the d i f f e r e n t i a l chemical influence of an o r i g i n a l surface ornamentation. The pattern of overlapping l i n e s on the t i p s of pleurae of Olenellus h a l l l (Waleott) figured by Waleott (1910, p i . 31, f i g s . 10, 11) show them to be roughly transverse on the ventral surface but sub- longitudinal on the d o r s a l . This rule appears to apply to a l l the species of Wannerla, Olenellus and Paedeumias i n the Garrett c o l l e c t i o n . GROWTH STAGES One of the most important phases of palaeon- t o l o g i c a l research, a f t e r the purely descriptive work has been done, i s the analysis of observations. Relation- 22 ships between groups are sought, and e f f o r t s made to disentangle evolutionary trends. The greatest use, both economic-and purely s c i e n t i f i c , can be made of informa- t i o n only when i t s l i m i t a t i o n s are known. The study of perhaps greatest taxonomic value i n paleozoology i s that of growth stages, f o r one of the most widely accepted-principles has been the biogenetic law; "Ontogeny recapitulates Phylogeny". The growth stages of only a few o l e n e l l i d s have been studied (Walcott, 1910). But the extent to which theories of evolution have been developed from such studies i s best i l l u s t r a t e d by reference to Raw (1925, 1927, 1936, 1937). But such theories should be accepted with some caution. I t i s possible that a t r i l o b i t e d i d not s t a r t to secrete hard parts capable of f o s s i l i z a t i o n u n t i l ^ l t s development was so f a r advanced as to provide only doubtful clues as to i t s r e l a t i o n s h i p s . Furthermore, some of the ontogenies des- cribed i n the past may have been based on i n s u f f i c i e n t specimens. Enough material i s present i n t h i s c o l l e c t i o n to warrant further work, but the writer regrets the lack of time to complete i t himself. An intensive study should be made of the growth 23. stages of,.Paedeumias and O l e n e l l u s i n t h i s c o l l e c t i o n , w i t h a view to confirming or c o n t r a d i c t i n g the c o n - c l u s i o n s reached "by Waleott ( 1 9 1 0 ) i n s o f a r as they apply to the fauna of the Eager Formation. PRESERVATION The O l e n e l l u s fauna i s n e a r l y always compara- t i v e l y w e l l preserved. Apart from the crushing of very t h i n , convex t e s t s , which i s to be expected even under the best c o n d i t i o n s , the f i n e sediments tend to preserve extremely f r a g i l e types of Crustacea such as the homopods Tuzola and Anomalooarls, and to favor the r e t e n t i o n of considerable d e t a i l i n the o l e n e l l i d s them- s e l v e s . The degree of p r e s e r v a t i o n has a very r e a l b e a r i n g on taxonomy. Removal of d i a g n o s t i c d e t a i l s , d i s t o r t i o n of s t r u c t u r e s , and even the superimposit ion of secondary c h a r a c t e r i s t i c s of inorganic o r i g i n , may a l l p l a y t h e i r p a r t i n making i d e n t i f i c a t i o n and c l a s s i - f i c a t i o n d i f f i c u l t . In the m a t e r i a l s t u d i e d here, a t t e n t i o n has been drawn to the almost complete absence of p y g l d i a . In t h i s connection, i t i s r e g r e t t a b l e that the t h o r a c i c segments of 0 . eagerensis are seldom preserved behind the 4 t h or 5 t h , and no p l e u r a l segments of Bonnla have been found at a l l . I t may be that the apparent absence 24. of i n t e r g e n a l spines i n l a r g e r specimens of Paedeumias i s a matter of incomplete p r e s e r v a t i o n . The extent of d i s t o r t i o n i n specimens i s often very d i f f i c u l t to estimate. I t i s reasonable, to assume that v a r i a t i o n s from a common "mean shape" e x i s t e d i n every c o n s p e c i f i c t r l l o b i t e p o p u l a t i o n . I f only one recognizable species were present , the v a r i a - t i o n s around the mean would fol low a normal d i s t r i b u - t i o n curve, with only one maximum p o i n t . However, i n the course of b u r i a l , compaction and s u b j e c t i o n to shearing s t r e s s e s , o r i g i n a l l y I d e n t i c a l forms might conceivably y i e l d i n a d e f i n i t e number of ways, l i m i t e d perhaps by the type of basic s t r u c t u r e . This c o u l d give r i s e to a s i m i l a r l y l i m i t e d number of "types". I t i s p o s s i b l e that some of the recognized species of t r i l o b l t e s owe t h e i r s p e c i f i c stature to such a combina- t i o n of mainly inorganic circumstances. The convex c e p h a l i c s h i e l d of an o l e n e l l i d i n course of f l a t t e n i n g , because i t i s wider than l o n g , may y i e l d more e a s i l y along the a x i s than l a t e r a l l y . Cracks are most l i k e l y to develop where greatest t e n s i o n i s e f f e c t i v e . Such a p o i n t appears to e x i s t at the f r o n t a l margin at the c e n t r e . Subsequently, the crack would extend backward over the cephalon, p e r m i t t i n g maximum 25. v e r t i c a l movement along the l i n e of maximum convexity, that Is, along the g l a b e l l a . Once the two halves were independent the next point of maximum tension would appear to l i e at or near the base of the palpebral lobe. In t h i s way i t i s possible to account f o r the commonly observed cephalic cracks: the primary fracture occurring along the axis, the secondary p a i r f o r t u i t o u s l y simula- t i n g the anterior branch of the f a c i a l suture. Compression acting i n the s o l i d rock may be quite intense, and i t s manifestation i n f o s s i l s can sometimes afford a measure of Its degree. Several specimens i n the c o l l e c t i o n show two or more cephala, d i f f e r e n t l y oriented, which exhibit d i s t o r t i o n . In some, the length to width r a t i o s d i f f e r from each other by as much as 40^. Pure compaction, on the other hand may lead to f a l s e length-width r a t i o s due. to the more intense l a t e r a l than l o n g i t u d i n a l y i e l d i n g of hemi- c y l i n d r i c a l structures such as the axis and g l a b e l l a . Not a l l notes on preservation are gloomy.. One natural cast of Olenellus c f . g i l b e r t 1 ( P l . I I Fig.10) shows two shallow, gently curved depressions tapering forward across the cheek from t h e i r o r i g i n „.at_the base of the palpebral lobes. Their p o s i t i o n and width appear to preclude confusion with " f a c i a l sutures", yet they are almost c e r t a i n l y of anatomical s i g n i f i c a n c e . Although 2&. apparently unsegmented, they are thought to he the Impressions of antennules. T h i s o b s e r v a t i o n confirms that of Dunbar, who s t a t e d (1925, p.. 306) that the antennae*1" of O l e n e l l u s " . . . a r e simple, p r o j e c t forward, and show no evidence of segmentation". CEPHALIC AND THORACIC RATIOS Because so many t r i l o b i t e s are d i s t o r t e d i t i s often impossible to gauge the o r i g i n a l shape of a s i n g l e specimen. S i m i l a r i t y of shape depends upon s i m i - l a r proportions of component p a r t s . On a d i s t o r t e d specimen the. r a t i o of length to width may be very m i s - l e a d i n g ; but the r e l a t i v e value of measurements made i n the same d i r e c t i o n tends to be constant f o r a species r e g a r d l e s s of d i s t o r t i o n . Working independently, the w r i t e r found that c e r t a i n c e p h a l i c r a t i o s were of d i a g n o s t i c v a l u e : the o v e r a l l width of the cephalon to that of the o c c i p i t a l r i n g , and the l e n g t h of the o c c i p i t a l and three lobes immediately a n t e r i o r to i t r e l a t i v e to that of the p a l - p e b r a l l o b e s . L a t e r , : t h i s system was modified t o b r i n g i t i n t o l i n e with the methods suggested by Lochman (1947, p . 60). The c e p h a l i c features f i n a l l y u t i l i z e d i n t h i s • 1 1. S i c 27 connection were: 1. R e l a t i v e p o s i t i o n of midpoint of eye r e l a t i v e to that of g l a b e l l a 1 . (Ibid) 2. Width of cheek from d o r s a l furrow to outside of genal angle r e l a t i v e to width of o c c i p i t a l r i n g . ( I b i d , modified f o r o l e n e l l i d s ) 3. Length of r e a r four c e p h a l i c l o b e s , i n c l u d i n g the o c c i p i t a l , to that of p a l p e b r a l l o b e s . 4. For the sake of completeness, the t h o r a c i c r a t i o , length of p l e u r a l groove to width of a x i a l lobe at the 2nd segment, i s Included here • TABLE I Cephalic and Thoracic R a t i o s Average values of 10 t y p i c a l - specimens of each species Species: 1 2 3 4- O l e n e l l u s eagerensis l e v e l 1.0-1.25 1.5-1*8 0.6-0.8 0 . s c h o f i e l d l behind 1.8-1.9 1.4-1.8 1.2-1.3 0 . c f . . g i l b e r t ! " 1.6-1>7 1.25-1.35 1.1-1'.2 Paedeumias nevadensis l' 1.7-1.9 1.25-1.35 D.l-1.2 (numbered columns r e f e r to sect ions In the text) SYSTEMATIC POSITION OF OLENELLIDS The f a c i a l suture as such does not appear to be present i n o l e n e l l i d s . But most of them do possess marginal s u t u r e s . The w r i t e r i s i n c l i n e d to agree with the f o l l o w i n g statement by Swinnerton (1919, p. 103): " T r i l o b i t e s i n common w i t h a l l other Arthropods shed t h e i r more or l e s s r i g i d e x t e r n a l covering or exoskeleton p e r i o d i c a l l y . To accomplish t h i s ecdysis. i t i s necessary f o r t h i s covering to s p l i t somewhere; and i t 28. i s h i g h l y probable t h a t t h e - . f a c i a l suture was the l i n e a l o n g which s u c h - s p l i t t i n g took p l a c e . There seems however t o be a - tendency to assume t h a t a l l l i n e s which ser v e d t h i s purpose are homologous. T h i s has i n t r o d u c e d unnecessary d i f f i c u l t i e s i n t o the study o f T r i l o b i t e c l a s s i f i c a t i o n . " S i nce the accepted method of c l a s s i f i c a t i o n does i n v o l v e f a c i a l s u t u r e s i t seems w i s e s t t o admit w i t h Poulsen (1932) and Resser (1938) the unique p o s i - t i o n of the o l e n e l l i d s and t o ac c o r d them the rank o f an o r d e r . Because O l e n e l l u s . as the f i r s t d e s c r i b e d genus, and one of the most w i d e l y d i s t r i b u t e d , appears t o be f i r m l y e s t a b l i s h e d as t y p i c a l , the c l a s s i f i c a t i o n f o l l o w e d here i n c l u d e s these t r i l o b i t e s i n the order O l e n e l l l d a . GENERIC AND SPECIFIC DISTINCTIONS Resser and Howell (1938) s t a t e t h a t s i n c e t he genotypes o f O l e n e l l u s and Mesonacls. 0. Thompson! and M. vermontana do not show s u f f i c i e n t d i f f e r e n c e s , the names "Mesonacls" and "Mesonacidae" must be dropped. They p o i n t out t h a t the d i f f e r e n c e between the p o s t e r i o r segments o f these s p e c i e s " e x i s t s and has some s i g n i f i - cance, but i t i s not now b e l i e v e d to be of g e n e r i c importance". ( I b i d . p. 217) Since the poor and i n f r e q u e n t p r e s e r v a t i o n o f 29. terminal segments has. l e d i n the past to so. much confusion, i t i s clear that they cannot constitute the p r i n c i p a l c r i t e r i o n f o r generic d i s t i n c t i o n . Other c r i t e r i a , based upon differences i n the cephalon and thorax must be used also . I t i s believed that s u f f i - cient difference exists between c e r t a i n species of Olenellus to j u s t i f y re-examination of the problem. I f "Mesonacls" were r e s t r i c t e d only to such comparatively d i s t i n c t species as 0. eagerensis, M. insolens, M. b r i s t o l e n s i s . and perhaps 0. vermontanus, a majority of the following c r i t e r i a might d i f f e r e n t i a t e such a genus from Olenellus or from Paedeumias. But, since the writer i s dependent on photographs rather than specimens from other l o c a l i t i e s , t h i s proposal i s made very tentatively'. TABLE II Possible Generic D i s t i n c t i o n s Characteristic Paedeumias Olenellus Mesonacls a. Posterior .segments . "4 ~~ 2-6 . 10 • b. Centres: eye to g l a b e l l a (1. p. 27) ' behind behind l e v e l c. L a t e r a l cephalic r a t i o ..(2-, p. 27) 1.6-1.9 1.8-1.9 1.0-1.25 d. Longitudinal cephalic . r a t i o (3, p. 27) 1.2-1.4 1.2-1.8 1.5-1.8 e. Lateral.thoracic r a t i o .(4, p. 27) 1.0-1.2 1.2-1.3 0.6-0.8 f . Glabellar shape c y l i n d r i c a l c y l i n d r i c a l "hour- May taper . .glass" forward g. Brim, anterior to . g l a b e l l a always sometimes never h. Stalk on hypostoma always never never 1. Intergenal spines always frequently reduced 30. RECOMMENDATIONS FOR FURTHER STUDY 1. A study should be made of the growth stages of O l e n e l l u s and Paedeumias i n the G a r r e t t c o l l e c t i o n , 2. I t i s p o s s i b l e t h a t two subspecies of O l e n e l l u s eagerensis are p r e s e n t , one with narrower cheeks, the other w i t h a more enlarged f r o n t a l lobe, than that described i n t h i s paper. This should be checked, 3» As i n d i c a t e d by Walcott (1910), Resser (1928) and as observed by t h e . w r i t e r , i t i s p o s s i b l e that O l e n e l l u s g i l b e r t ! i s a '"form species" comprising l e g i t i m a t e species of Paedeumias.as w e l l as O l e n e l l u s , Resser ( I b i d . p . -9) states^: " i t seems c e r t a i n . . . that some of the specimens r e f e r r e d by authors to Mesonacls g i l b e r t ! belong n e i t h e r to that species nor even t o Mesonacls. but are d i s t i n c t species of Paedeumias." This species should be thoroughly re-examined, 4. As i n d i c a t e d i n t h i s paper, i f the generic d i s t i n c t i o n s o u t l i n e d by Lochman (1947, p . 60) are fol lowed, at l e a s t one.new genus must be erected on the b a s i s of c e p h a l i c c h a r a c t e r i s t i c s . (See p . 29) This may involve the r e - e x a m i n a t i o n . o f generic d i s - t i n c t i o n s a n d . r e c l a s s i f i c a t i o n of the whole order O l e n e l l l d a . 31. CHAPTER III DESCRIPTION OF GENERA-AND SPECIES Phylum Arthropoda Class Crustacea Subclass T r i l o b l t a Order O l e n e l l l d a Family Olenellidae Genus Olenellus H a l l , 1862 Barrandia H a l l N.Y. State Cab. Nat. Hist., 13th Rept. (1860) p. 115. Olenellus H a l l N.Y. State Gab. Nat. H i s t . , 15 Rept. (1862) p. 114. Mesonacls Walcott Am. Jour. S c i . , 3rd ser., v o l . 29, . (1885) p. 328, f i g . 1, 2. Olenellus Walcott U.S. Geol. Surv., B u l l . 30, (1886) p. 162, I65. Mesonacls Walcott U.S. Geol. Surv., B u l l . 30, (1886) p. 158, 165. Olenellus Walcott U.S. Geol. Surv., 10th Ann. Rept. (1891) p. 165 , -633. Mesonacls Walcott-U.S. Geol. Surv., 10th Ann. Rept. (1891) p. 637. Mesonacls Walcott Smithsonian Misc. C o l l . , V o l . 53, no. 6 (1910) p. 246, 261. Olenellus Walcott Smithsonian Misc. C o l l . , v o l . 53, no. 6 (1910) p. 248, 311. Mesonacls Resser Smithsonian Misc. C o l l . , v o l . 81, no. 2 (1928) p. 3 . Olenellus Resser Smithsonian Misc. C o l l . , v o l . 81, no. 2 (1928) p. 5 . Olenellus Resser and Howell, B u l l . Geol. Soc. Amer., v o l . 49, (1938) p. 217, 218. The most recent authoritative work on o l e n e l l i d s i s that by Resser and Howell (1938). U n t i l a great deal more much needed study has been made of the whole order i t i s - c l e a r that t h e i r generic diagnoses of Olenallus and Paedeumias. must stand as p a r t i a l c l a r i f i c a t i o n of what 32. had been taxonomic chaos. But the writer, faced with a fauna i n which c e r t a i n species assigned to Olenellus show closer a f f i n i t i e s to Paedeumias than to other species placed i n t h e i r own genus, i s bound to suggest a l t e r n a t i v e grouping. I t i s probable that e i t h e r a r e s t r i c t e d genus Mesonacls w i l l have to be revived, or that the genus Paedeumias. w i l l have to be greatly enlarged at the ex- pense of Olenellus; indeed; i t i s possible that both expedients w i l l be necessary. The following generic diagnosis of Olenellus i s summarized and s l i g h t l y modified from Resser and Howell (1938, p. 217). Diagnosis The cephalon i s large; the thorax, of many segments, i s long and tapering; the pygidium i s repre- sented by a small p l a t e . Cephalon usually semicircular, highly convex, with long genal spines. F a c i a l sutures not f u n c t i o n a l . Glabella wide, extending to f r o n t a l rim, either c y l i n - d r i c a l or "hourglass" shaped. Of the three pairs of g l a b e l l a r furrows, the f i r s t connects across the middle, setting o f f the rounded f r o n t a l lobe; the second i s frequently reduced to a p a i r of s l i t s , which i n adults 33. f a i l to reaoh the d o r s a l furrow; the t h i r d p a i r of furrows, l i k e the o c c i p i t a l behind i t , f a i l s to connect across the g l a b e l l a . The d o r s a l furrow i s deep, but i n t e r r u p t e d by the j u n c t i o n of the f r o n t a l and p a l p e b r a l l o b e s . The brim i s narrow, often only equal to the width of the marginal furrow. Rim v a r y i n g i n width between s p e c i e s , u s u a l l y f a i r l y narrow, widening s l i g h t l y toward the genal a n g l e s . P a l p e b r a l lobes s e m i c i r c u l a r , separated from the g l a b e l l a by the d o r s a l furrow (and p o s t - o c u l a r nodes i f p r e s e n t ) . Eyes large and, l i k e the p a l p e b r a l l o b e s , may extend almost to the p o s t e r i o r margin. F a c i a l sutures are not present as such, but p o s s i b l y are represented p o s t e r o - l a t e r a l l y by r a i s e d , sometimes asymmetrical and b i f u r c a t i n g l i n e s , running from under the eyes toward the genal a n g l e s . Cheeks are large and convex. Intergenal spines often p r e s e n t . Genal spines u s u a l l y l a r g e , but smaller when i n an advanced p o s i t i o n . Hypostoma s t r o n g l y convex, about the same s i z e as the f r o n t a l l o b e , attached d i r e c t l y to a narrow j epistomal plate'* Thoracic segments v a r y i n g i n number, but f i x e d w i t h i n a s i n g l e s p e c i e s , u s u a l l y l o o s e l y arranged. Pleurae 54. s t r a i g h t , sharply curving back to long t a p e r i n g ends. P l e u r a l grooves wide and s t r a i g h t to the fulcrum, where they bend s l i g h t l y l e s s sharply than the p l e u r a e , and begin to contract s l i g h t l y more abruptly than the p l e u r a l terminations* The f u l c r a l angle and tapered terminations increase p o s t e r i o r l y i n p r o p o r t i o n to the decreasing l e n g t h of the p l e u r a e . The r e a r seg- ments p o i n t almost d i r e c t l y backward, p a r t l y e n c l o s i n g the large a x i a l spine on the 15th segment. Varying numbers of small segments p o s t e r i o r to the 15th are terminated by a p y g i d l a l p l a t e . These segments are often c a l l e d rudimentary because they often l a c k p l e u r a l extensions. Except f o r the f i f t e e n t h segment, a x i a l spines are u s u a l l y absent. Surface may be i r r e g u l a r l y l i n e d . O l e n e l l u s i s most e a s i l y confused w i t h Paedeumias. from which i t d i f f e r s " . . . c h i e f l y i n the p o s i t i o n and s i z e of the g l a b e l l a , i n the wider doublure, and i n the d i r e c t attachment of the hypostoma to the marginal p l a t e , without the s lender s t a l k of Paedeumias" (Resser and Howell , p . 2 1 8 ) . Genotype: O l e n e l l u s thomnsoni H a l l 1862 35 OLENELLUS o f , GILBERTI MEEK, 1874 F r o n t i s p i e c e ; Plate I I , F i g s . 6-10. This i s one of the commonest, species present i n the Eager Formation. One of the b e t t e r preserved specimens i s i l l u s t r a t e d as the F r o n t i s p i e c e . From observations of 0 . c f . g i l b e r t l and from statements made by competent workers ( I b i d p . 226) i t may be i n f e r r e d that the presence of a b r i m of considerable width s e p a r a t i n g a narrow r i m from the g l a b e l l a i s i n d i c a t i v e of a s t a l k e d hypostoma. I f t h i s i s so, many species now assigned to O l e n e l l u s should be t r a n s f e r r e d to Paedeumias. Of these, 0 . g i l b e r t ! , as f o r e c a s t by Waleott (1910, p . 329) and by Resser (1928, p . 9) should almost c e r t a i n l y be one of the f i r s t . However, s ince f u r t h e r study, both of the type specimens and of the e x c e l l e n t l y preserved f o s s i l s from the Eager Formation, i s p r e r e q u i s i t e to such a step, i t seems wisest to take no c o n t r o v e r s i a l a c t i o n at t h i s t ime. Diagnosis Apart from the presence of a b r i m , whose width v a r i e s from equal to twice that of the r i m , the cephalon conforms to generic d e s c r i p t i o n . Intergenal spines subdued or absent i n specimens l a r g e r than 15 mm i n w i d t h . The shortness of the p a l p e b r a l lobes i s masked to a c e r t a i n extent by long, low p o s t - o c u l a r mounds. Marginal 3 6 . and intramarginal sutures present. Rim f a i r l y narrow, but varies s l i g h t l y between individuals j i t widens f a i r l y strongly at the genal angles. Epistomal plate the same width as rim at the front, tapering gently toward the genal angles. Small node or spine on pos- t e r i o r of o c c i p i t a l lobe. Pleurae of t h i r d thoracic segment greatly enlarged making nearly a r i g h t angle at the fulcrum. Single small spines on the posterior margins of a x i a l lobes are traceable forward, progressively reducing i n size from the 14th segment t i l l they die out altogether at the 3rd. The a x i a l spine on the 15th segment i s very large and long, presenting a curious dimpled structure; the minute depressions are arranged i n quincunx. Rudimentary segments were very doubtfully observed on only one specimen; no l e s s than three appear to be present. Cephalic and thoracic r a t i o s are given i n Table I. Relationships The most nearly a l l i e d forms are those assigned to Olenellus g i l b e r t l Walcott, Paedeumias nevadensis (Walcott) and P. c l a r k i Resser. 37. This species d i f f e r s from 0. g l l b e r t l i n having shorter p a l p e b r a l l o b e s , and c e r t a i n i n d i c a t i o n s of a s t a l k e d hypostoma. From- P. c l a r k i i t d i f f e r s i n possessing a wider r i m . From P. c l a r k i and P . nevadensls i t d i f f e r s i n having a narrower b r i m , a more expanded f r o n t a l lpbe, and i n l a c k i n g i n t e r g e n a l spines when a d u l t . OLENELLUS EAGERENSIS n . sp. Plate I , F i g s , 1-11* The most s t r i k i n g feature of 0 . eagerensis i s the great width of the axis' . Cephalon i s s e m i c i r c u l a r i n f r o n t ; p o s t e r i o r margin with c l e a r l y developed i n t e r g e n a l angle of about 145° i n a d u l t s , l e s s c l e a r l y marked i n young specimens. Advanced, f a i r l y small genal s p i n e s , always oblique to the a x i s by an angle of about 20°. G l a b e l l a "hourglass" shaped, with s t r o n g l y convex s e m i - e l l i p s o i d a l f r o n t a l lobe touching the r i m . Both f r o n t p a i r s of g l a b e l l a r furrows i n a d u l t s reduced t o s l i t s , the second almost to dimples; i n immature forms these two furrows connect across the middle, but the second p a i r does not extend to the d o r s a l furrow. P a l p e b r a l lobe i s s h o r t , s t r o n g l y arched, i t s t i p extending to j u s t behind the t h i r d g l a b e l l a r furrow. Rim i s very narrow, widening only s l i g h t l y at the genal a n g l e . P o s t e r i o r r i m shallow, 38, widened at the Intergenal angle. Small i n t e r g e n a l spines are sometimes f a i n t l y developed j u s t outside i n t e r g e n a l angles; even when absent, they are r e p r e s e n - ted by a s l i g h t t h i c k e n i n g of the r i m , which i s j o i n e d by a low r i d g e to the back of the p o s t - o c u l a r mounds opposite the o c c i p i t a l furrow. O c c i p i t a l r i n g wide, with a small p o s t e r i o r s p i n e . Thorax with broad a x i s . P l e u r a l lobes comparatively s h o r t , sharply a n g l i n g back and a b r u p t l y t a p e r i n g to short s p i n e s . P l e u r a l grooves s h o r t , broad, f l a t , marked off d i s t i n c t l y b y . a r i m b o t h a n t e r i o r l y and p o s t e r i o r l y . Pleurae of t h i r d segment not g r e a t l y enlarged; Small a x i a l spines present on a l l t h o r a c i c segments a n t e r i o r to the 1 5 t h ; the l a t t e r spine i s enlarged, but tapers s h a r p l y . Nothing i s known of s e g - ments, or pygidium, p o s t e r i o r t o the 1 5 t h . Cephalic and t h o r a c i c r a t i o s are given i n Table I . Holotype:: Department of Geology, U n i v e r s i t y of B r i t i s h Columbia, No. GT 101. C o l l ; : C. G a r r e t t . Paratypes: Department of Geology, U n i v e r s i t y , of B r i t i s h Columbia, Nos. GT 1 0 2 - 110. C o l l : : C . G a r r e t t . Type L o c a l i t y : L o c . B. Eager Formation, 6 m i . N . E . of Granbrook, B . C . Geologic Age: Lower Cambrian. 3 9 . Discussion This species of Olenellus shows such s t r i k i n g differences from the genotype, that were the recommen- dations of Lochman (1947) followed, i t would probably be placed i n a d i f f e r e n t genus. Its closest a f f i n i t y to figured species i s to the drawings reproduced by Walcott (1910, p i . 37, Figs. 8-19) from his previous publications (1884, 1886, 1891) purporting to show the young stages of growth of 0. fremontl. The l a t t e r species has been r e s t r i c t e d by Resser ( 1 9 2 8 ) and proven not to possess advanced genal spines. 0. eagerensls d i f f e r s from Walcott's figures i n having a narrower rim, smaller genal spines, shorter anterior lobe, and wider, more evenly tapering palpebral lobes; but i t s s i m i l a r i t y i s apparent i n view of Walcott's own tentative i d e n t i f i c a t i o n of "0. of. fremontl" from the Eager Formation (Schofield, 1 9 2 2 , p. 1 2 ) . From "Mesonacls" b r l s t o l e n s i s and "M". insolens (Resser, 1928) i t d i f f e r s i n having l e s s advanced genal spines, wider intergenal angles, narrower rim, and more rounded f r o n t a l lobe. From 0. vermontanus i t d i f f e r s i n having s l i g h t l y shorter palpebral lobes, narrower rim, 4 0 . sharper i n t e r g e n a l angles, and a s l i g h t l y wider cheek. From other o l e n e l l i d s i n the c o l l e c t i o n the quoted d i f f e r e n c e s are even more marked. This species i s w e l l represented i n the c o l - l e c t i o n , and i s based on no l e s s than one hundred cephala ranging from 2.4 to 35 mm. i n w i d t h . I t i s named f o r the Eager Formation i n which i t i s found. OLENELLUS SCHOFIELDI n . sp. Plate I , Figs." 12-17. Cephalon s e m i c i r c u l a r , s l i g h t l y t r a p e z o i d a l i n elongated specimens, with an almost s t r a i g h t p o s t e r i o r margin. G l a b e l l a narrow, c y l i n d r i c a l , with expanded h e m i s p h e r i c a l f r o n t a l lobe reaching the r i m . G l a b e l l a r furrows normal f o r genus; second p a i r reduced to s l i t ' s . P a l p e b r a l lobes extremely s h o r t , t h e i r t i p s extending to opposite the f r o n t h a l f of the 3rd g l a b e l l a r lobe behind the f r o n t a l . ' P o s t - o c u l a r nodes very prominent and s h o r t , rounding down abruptly behind t h e i r p o i n t of maximum e l e v a t i o n opposite the back of the 3rd g l a b e l l a r l o b e . Rim very narrow, h a r d l y widening at a l l toward the genal angle. Genal spines s l e n d e r . Intergenal spines present , j o i n e d to back of p o s t - o c u l a r mounds by 41. a s l i g h t l y r a i s e d r i d g e . A minute o c c i p i t a l spine may be present. Thorax t y p i c a l of the genus, but the a x i s , somewhat narrow a n t e r i o r l y , appears to taper r a t h e r g r a d u a l l y . Pleurae angling back sharply to slender t e r m i n a t i o n s . T h i r d pleurae s t r o n g l y enlarged. Small a x i a l spines are present on segments p o s t e r i o r to the f i f t h . - - Rudimentary segments and pygidium unknown. Venation of the cheek surface i s s t r i k i n g l y developed on the l a r g e r forms, c o n s i s t i n g of r a d i a t i n g , i r r e g u l a r l y i n o s c u l a t i n g , r a i s e d l i n e s . The l a r g e s t cephalon assigned to t h i s species i s 32.6 mm. wide by 17«1 mm. l o n g . The r a t i o of width to l e n g t h (1 . 9 ) f o r t h i s specimen i s b e l i e v e d to be a l i t t l e h i g h ; two other cephala o r i e n t e d almost exact ly at r i g h t angles y i e l d an average r a t i o of 1.8. Other c e p h a l i c and t h o r a c i c r a t i o s are g i v e n i n Table I . Holotype: Department of Geology, U n i v e r s i t y of B r i t i s h Golumbia No. GT 201. C o l l : C. G a r r e t t . Paratypes: Department of Geology, U n i v e r s i t y of B r i t i s h Columbia, Nos. GT 202- 210. O o l l : . : C . G a r r e t t . Type L o c a l i t y : L o c . B, Eager Formation, 6 mi. N . E . of Cranbrook, B . C . Geologic Age: Lower Cambrian. 42 Discussion The shortness of palpebral lobes, the pro- minent post-ocular nodes, the strongly developed venation and extremely narrow rim serve to d i s t i n g u i s h 0. schofieldi'from a l l other c o r d i l l e r a n species. From 0 . brevoculus i t i s distinguished by . i t s having a narrower rim and r e l a t i v e l y narrower g l a b e l l a , and from 0 . fremontl (s.s.) by the narrow rim, stra i g h t posterior cephalic margin and possession of intergenal spines. This species i s comparatively rare, only ten specimens being d e f i n i t e l y assignable to i t i n t h i s c o l l e c t i o n . I t i s named afte r S.J. Schofield of the Geological Survey of Canada who f i r s t reported the pre- sence of o l e n e l l i d s near Cranbrook. GENUS PAEDEUMIAS WALCOTT 1910 Paedeumias Walcott, Smithsonian Misc. C o l l . , v o l . 53, . no. 6 (1910 p. 304. Paedeumias Resser, Smithsonian Misc. C o l l . , v o l . 81, no. 2 (1928) p. 5 Paedeumias Resser and Howell, B u l l . Geol. Soc. Amer., v o l . 49, no. 2 (1938) p. 225. The redescription of t h i s genus by Resser- and Howell (1938 p 225) expresses the e s s e n t i a l c h a r a c t e r i s t i c s : "The cephalon- i s large and broad, the thorax has many long-splned segments and terminates 43. i n a small p l a t e . The cephalon i s s e m i c i r c u l a r i n o u t l i n e , and probably- had considerable convexity. F a c i a l s u t u r e s 1 are sometimes t r a c e a b l e back of the eyes. G l a b e l l a g e n e r a l l y - c y l i n d r i c a l with the a n t e r i o r lobe tapered r a t h e r b l u n t l y , and s i t u a t e d some d i s t a n c e from the r i m . The d o r s a l furrows are w e l l impressed except where the eyes J o i n . Rim u s u a l l y narrow (never wide), i n c r e a s i n g but s l i g h t l y toward.the genal angles. A r i d g e connects the median p o i n t of the a n t e r i o r g l a b e l l a r lobe w i t h the r i m , but i t i s p o s s i b l e that t h i s feature d i d not always show on the l i v i n g animal, r e s u l t i n g from compression of the test, on to the" hypostoma.stalk d u r i n g f o s s i l i z a t l o n . Eyes l a r g e , extending almost to the r e a r m a r g i n ; ! the outer curved edge, and perhaps a l s o the r e a r p o r t i o n of the eye l o b e s , were r a i s e d free above the cheek s u r f a c e s . Genal spines s l e n d e r , i n a d u l t i n d i v i d u a l s , extending t o about the t h i r d or s i x t h p l e u r o n . Intergenal spines present i n , a l l species now d e f i n i t e l y assigned to the genus. The hypostoma i s attached to the marginal or, .more l i k e l y , epistomal p l a t e , by a s t a l k whose l e n g t h equals the distance from the g l a b e l l a t o the r i m . The hypostoma i t s e l f i s t y p i c a l f o r the f a m i l y , having f i v e or more t e e t h oh each side of the median l i n e . The p l a t e to which the hypos- toma i s attached frequently breaks away, sometimes, i n such a manner as to i n d i c a t e a hinged attachment between the genal angles and the i n t e r g e n a l s p i n e s . Thorax apparently has nineteen segments. The f i r s t f i f t e e n are normal i n shape, with the t h i r d g r e a t l y enlarged. A long heavy spine i s present on the f i f t e e n t h p l e u r o n . 1 Back of t h i s the York species shows four r a t h e r simple segments and f i n a l l y a s m a l l p y g i d i a l p l a t e . Small spines, i n c r e a s i n g s l i g h t l y i n s i z e rearward, are present on the s i x or more segments immediately before the f i f t e e n t h . 1. S i c 44. Surface f a i n t l y l i n e d i n the usual fashion, Paedeumias d i f f e r s l i t t l e from Olenellus except i n the p o s i t i o n of the g l a b e l l a and the stalked hypostoma. Genotype; P. transltans walcott, 1910" To the above diagnosis l i t t l e can be added, but the palpebral lobes and eyes of at l e a s t one species, P. nevadensis. are short and extend no further back than the o c c i p i t a l furrow* S i m i l a r l y the writer main- tains personal reservations concerning i n t e r p r e t a t i o n of l i n e s back of the eyes as f a c i a l sutures*. PAEDEUMIAS NEVADENSIS (Walcott) ' P l a t e I I , Pigs. 1-5. " ' Oallavia ? nevadensis .Walcott, 1910 (pars) Smithsonian Misc. C o l l . , vol..53, No. 6 p. 285, p i . 38, Pig. 12. paedeumias nevadensis Resser, (1928) Smithsonian Misc. C o l l . , v o l . 81, No. 2, p. 9, p i . 3, F i g s . 3-7. The main s p e c i f i c c h a r a c t e r i s t i c s are: the bl u n t l y tapering g l a b e l l a , short palpebral lobes, exten- ding no further than opposite the o c c i p i t a l furrow, and wide brim, about 3 to 4 times the width of the rim. P=*~nevadensis i s e a s i l y confusible with Olenellus cf. g i l b e r t ! i n the Eager Formation. These species apparently overlap i n width of brim, s i z e of 4 5 . ' f r o n t a l and palpebral lobes, and i n development of a x i a l and intergenal spines. Furthermore, the Immature specimens i n the c o l l e c t i o n are p r a c t i c a l l y a l l of the Paedeumias type, and at t h i s stage i n the research could, with equal f a c i l i t y , be re f e r r e d to 0. o f . K l l b e r t l . P. nevadensis. or i n some cases to P~. c f . c l a r k i . This gives point to the suggestion that these forms, i f not conspecific; are here i n the process of separating into d i s t i n c t species. I t i s believed that a thorough s t a t i s t i c a l analysis, based on several fea- tures, i s necessary to check t h i s suggestion. GENUS WANNERLA WALCOTT, 1910 Wannerla Waleott. Smithsonian Mlso. C o l l . , v o l . 57, No. 6 (1910) p. 248, 296. Wannerla Resser and Howell, B u l l . Geol. Soc. Amer., v o l . 49, No. 2, (1938) p. 227. The following diagnosis i s based on Resser and Howell (Ibid) and on personal observation. Entire t r i l o b l t e ovate, with large, semicir- cular, highly convex, t h i n cephalon, which i s usually severely f l a t t e n e d i n adult specimens. Glabella strongly expanded a n t e r i o r l y and touching rim. Dorsal furrow deep on thorax but poorly impressed on cephalon. Glabellar and o c c i p i t a l furrows s i m i l a r to those of 46. O l e n e l l u s . but shallower. O c c i p i t a l r i n g with short s p i n e . Rim wide, i n c r e a s i n g r a p i d l y toward genal a n g l e s . G-enal spine s t r o n g , r a t h e r l o n g , t a p e r i n g r a p i d l y . P a l p e b r a l lobes s h o r t , sharply bowed. Hypostoma l a r g e , u s u a l l y l a t e r a l l y and p o s - t e r i o r l y toothed, attached d i r e c t l y to epistomal p l a t e . This p l a t e i s wide, and toothed along i t s inner edge. Epistomal and marginal, p l a t e s attached throughout f u l l l e n g t h of the former. Both p l a t e s may be s t r i a t e d ^ but the epistomal p l a t e often shows a r e t i c u l a t e surface 1 . Thorax i n the type species of seventeen s e g - ments, which decrease r e g u l a r l y i n s i z e , except the l a s t two, which are markedly s m a l l e r . D o r s a l and a x i a l furrows deeply Impressed. The f i r s t fourteen a x i a l r i n g s have.short s p i n e s , p r o g r e s s i v e l y longer toward the r e a r . The f i f t e e n t h segment has a very strong a x i a l s p i n e , but the two p o s t e r i o r segments l a c k s p i n e s . Segments n e a r l y s t r a i g h t to fulcrum, with wide p l e u r a l furrows, which taper g r a d u a l l y , terminating b l u n t l y at the fulcrum. P l e u r a l extensions curve backward and taper to sharp points;* Pygidium, a s m a l l , s l i g h t l y b l l o b a t e p l a t e , with a median r i d g e , surrounded by t i p s of r e a r t h o r a c i c segments1. 47. Surface of e n t i r e t r i l o b l t e coarsely r e t i - c u l a t e , except marginal p l a t e , which i s s t r i a t e d or s c a l y . • Wannerla i s d i s t i n g u i s h e d from a l l other o l e n e l l i d s by a unique combination of f e a t u r e s : expan- d i n g g l a b e l l a , normal t h i r d t h o r a c i c p l e u r a e , large 15th spine, and coarsely r e t i c u l a t e s u r f a c e . Genotype: O l e n e l l u s (Holmla) waloottanus. Wanner,. 1901 Rangej Lower Cambrian of North America and Greenland. WANNERIA WALCOTTANA (WANNER) , Plate I I , F i g s . 11-18. O l e n e l l u s (Holmla) waloottanus Wanner, Washington Acad:-Sci Pr No'.-3'(1901) p 267, p i . 31, F i g s . 1, 2 ; ; p i . 32, F i g s . 1-4. Wanheria waloottanus Walcott ( p a r t ) , Smithsonian '" ™ V. . Misc.." C o l l . , v o l . 53, No. 6 (1910), p . 302, - p i . 30, F i g s . 1, 2, 5-12J p i . 31, F i g s . 12, 13; p i . 44, F i g . 6. Wanneria walcottana Walcott, Smithsonian M i s c . C o l l . , v o l . 64, No. 3 , (1916) p . 219, p i . 38, F i g s . 1, 2. Wanneria walcottana Resser and Howell , B u l l . G e o l . Soc. Amer., v o l . 49, No. 2 (1938) p . 228, p i . 9, F i g s . 9, 10;; p i . 10,.Figs. 8-10; p i . 11. _ Diagnosis: One of the l a r g e s t of the o l e n e l l i d s , up to 17 cm. i n width. Cephalon strongly convex. Marginal 48. furrow deep'. Broad r i m , terminating i n large genal s p i n e s . G l a b e l l a t y p i c a l of genus. Strongly convex f r o n t a l lobe, expanded to one t h i r d width of cephalon. O c c i p i t a l lobe s l i g h t l y wider than p o s t e r i o r g l a b e l l a r lobes, r i s i n g sharply towards the r e a r . O c c i p i t a l spine may be p r e s e n t . D o r s a l , g l a b e l l a r , and o c c i p i t a l furrows shallow. P a l p e b r a l lobes deeply e r e s c e n t i c , h i g h l y convex, s h o r t , and t a p e r i n g to t h e i r t e r m i n a - t i o n opposite the l a s t g l a b e l l a r l o b e . Marginal sutures as i n O l e n e l l u s . Hypostoma large and d e n t i c u l a t e . Thorax t y p i c a l of genus. F a l c a t e p l e u r a l terminations marked with f i n e , curved, overlapping s t r i a e , roughly transverse v e n t r a l l y and s u b - l o n g i t u d i n a l d o r s a l l y , as i n O l e n e l l u s . P l e u r a l grooves are wide, gently t a p e r i n g troughs, terminating somewhat b l u n t l y at the fulcrum. Segments p o s t e r i o r to the 15th, and pygidium, t y p i c a l of genus. Surface r e t i c u l a t e , the coarseness of the polygonal network v a r y i n g d i r e c t l y w i t h s i z e of specimen, not u s u a l l y v i s i b l e on those smaller than' 25 mm. i n w i d t h . More than 100 specimens are present I n the c o l l e c t i o n , ranging i n width from 2«5 mm. to 12 cm. In young specimens the convexity i s s t r i k i n g . During growth the comparative width of the r i m appears to decrease. 49. Immature forms tend to c u r l up; segments posterior to the 12th are usually concealed f o r t h i s reason. The adult W. waloottana from Granbrook seem* to d i f f e r from those i n the eastern part of the continent In two d e t a i l s : hypostomae appear to lack teeth, and spines are absent from the o c c i p i t a l r i n g and from thoracic segments anterior to the 15th. I f these apparent differences are proven to be r e a l , the choice w i l l have to be made between r a i s i n g these specimens- to s p e c i f i c rank, or recognizing that d e n t i c u l a t i o n of the hypostoma i s a feature only of subspeclfic value i n c l a s s i f i c a t i o n . Order Op.isthoparida Superfamlly Corynexochoidae Family .Gorynexochidae Genus Bohnia Waleott, 1916 Gorynexochus„.(Bonnla). Waleott, Smithsonian Misc. . C o l l . , v o l . 64, No. 5 (1916) p. 325. Bonnia Raymond, Amer. Jour. S c i . , 5th ser. v o l . 15, No. 88 (1928) p. 309. Bonnla Resser, Smithsonian Misc. C o l l . , v o l . 95, No. 4 (1936) p. 6. Bonnia Lochman, Jour. Paleontology, v o l . 21, No. 1 (1947) p. 68. "Granidium: If. Palpebral lobes medium size , back of midline of g l a b e l l a but not quite as f a r back as one-third. 5 0 . 2 . G l a b e l l a either, p a r a l l e l - a i d e d or expanding slowly to a broad f r o n t ; regular, convexity; f i r s t two p a i r s of g l a b e l l a r furrows, often o b s o l e t e , p o s t e r i o r p a i r sometimes w e l l d e f i n e d ; o c u l a r r i d g e obsolete In about o n e - h a l f .the species'. 3 . F i x e d cheeks approximately o n e - h a l f (may be a l i t t l e more) width of g label la; . 4 . F i x e d cheeks h o r i z o n t a l or very s i g h t l y downsloping 5 . P o s t e r o l a t e r a l limbs s l i g h t l y l e s s than l e n g t h of o c c i p i t a l r i n g ' . 6 . No f r o n t a l l i m b , a convex f r o n t a l border,, marginal furrow at s i d e s o n l y . Pygidium: 1. Nearly s e m i c i r c u l a r i n o u t l i n e , 1, 2 or three p a i r s of a n t e r i o r marginal s p i n e s . 2. P l e u r a l lobes same width as a x i a l l o b e , a narrow marginal furrow, a narrow but d i s t i n c t marginal b o r d e r . 3* A x i a l lobe of medium width, - c y l i n d r i c a l i n shape, extending to b o r d e r , three c l e a r , one f a i n t segment and a t e r m i n a l p o r t i o n . " 1 (Lochman,. 1947 p . 68-69) Genotype: Bathyurus parvulus B i l l i n g s , 1861 Range: Lower Cambrian, North America and A s i a BONNIA c f COLUMBENSIS RESSER . P l a t e I I , F i g s . 1 9 , 2 0 . Corynexochus (Bonnia) senectus Walcott ( p a r t ) , Smithsonian M i s c . C o l l . ; , v o l . 64,- No. .5 (1916) p . 319, p i . 5 5 , F i g s . 7 - 7 c Bonnia columbensis Resser f Smithsonian M i s c . , C o l l . , v o l . 9 5 , No. 4 (1936) p . 9 51. Two poorly preserved c r a n i d i a and one pygidium are present i n the c o l l e c t i o n , conforming to generic description. Tentative s p e c i f i c i d e n t i f i c a - ^ t i o n was made by reference to the works c i t e d , especia- l l y by comparing with photographs by Waleott (1916). Apparently .this :was the form Waleott i d e n t i f i e d as Prototypus seneetus (Schofield 1922, p. 12). 52. .SELECTED BIBLIOGRAPHY Beecher, C.E. (1897) Outline of a natural c l a s s i - f i c a t i o n of t r i l o b l t e s ; Am. Jour...Sci., ser. 4, v o l . 3, pp. 89-106, 181-207. B e l l , G.K. (1931) Disputed structures of the Mesonacidae and.their.significance; Am. Mus. Novitates, no. 475, pp. 1-23. Burling, L.D. (1914) Ear l y Cambrian stratigraphy in.-the North .American, c o r d i l l e r a ; Geol. Surv. Canada, Mus. B u l l , now-2, ppv 93-129. (1916) Paedeumias, and the Me sonacidae with description of a-new species, having a t . l e a s t 44 segments, from the Lower Cambrian of B r i t i s h Columbia; Ottawa Nat.-,.vol. 30, no. 5, pp. 53-58. Deiss, C. (1939) Cambrian formations of south- western Alberta and southeastern B r i t i s h Columbia; B u l l . Geol. Soc. Amer., v o l . 50, pp. 951-1026. (1940) Lower and Middle Cambrian stratigraphy of southwestern and southeastern B r i t i s h Columbia; B u l l . Geol. Soc. Amer., v o l . 51, pp. 731-794. Dunbar, CO. (1925) Antennae i n Olenellus g e t z i . ti.sp.; Am. Jour. S c i . , ser. 5, v o l . 9, -pp. 303- 308. Evans, C.S. (1932) Brisco-Dogtooth Map-Area, B r i t i s h Columbia; Geol. Surv. Canada, Sum. Rept., pt. A l l , pp. 160-175. H a l l , J . " (1859) Trilob-ites of the shales of .the Hudson River Group; Ann.. Rept. N.Y. State Cab. Nat. H i s t . v o l . 12, pp. 59-62. (1862) Supplementary note to the .. thirteenth, report of the regents of the state cabinet; Ann. Rept. N.Y. State Cab. Nat. H i s t , v o l . 15, p. 114. Howell, B.F., et a l . (1947) Terminology f o r describing Cambrian t r i l o b i t e s ; Journ. paleontolV, v o l . 21, pp. 72-76. Keen, A.M. and Muller, S.W. (1948) Procedure i n Taxonomy; ..Stanford Univ. Press'. 53. Poulsen, C. (1927) The Cambrian, Ozarkian and Canadian faunas of.northwest Greenland; Medd. Gronland, v o l . 70, pp. 237-343. (1932) The Lower Cambrian'faunas of . east Greenland; Medd. Gronland, vol.-87, no. 6, pp. 1-66. Rasetti, F. (1948) Lower Cambrian t r i l o b i t e s from the conglomerates of Quebec; Journ. Paleontol., v o l . 22, pp. 1-24. . (1951) Middle Cambrian stratigraphy and faunas of_the Canadian Rocky Mountains; Smithsonian Misc. C o l l . , v o l . 116, no. 5, PP« 1-270. Raw, F. -i (1925) The development of Leptoplas- . tus Salter1 and' o t h e r . t r i l o b i t e s ; Geol. Soc. London,. Quart. Jour'., v o l . . 81, pp. 223--324. (1927) Ontogenies of t r i l o b i t e s and t h e i r s i g n i f i c a n c e ; Am. Jour. Sci 1., v o l . 14, no. 78, pp. 7-35; no, 80,.pp. 131-149. . (1936) Mesonacidae of Comley i n Shropshire, with a-dlscussion of c l a s s i f i c a t i o n within the group; Geol. Soc. London, Quart. Jour., vol.-92, pp. 236-293. - ' i (1937) Systematic p o s i t i o n of the Olenellldae (Mesonacidae); Journ. Paleontol., v o l . 11, no..7, pp. 575-597. Raymond,... P.E.-- (1917)} Beecher's c l a s s i f i c a t i o n of -- t r i l o b i t e s a f t e r twenty years; Am. Jour. S c i . , v o l . 43, pp. 196-210. . . (1928) Ontogenies of t r i l o b i t e s and t h e i r s i g n i f i c a n c e ; Am. Jour. S c i . , ser. 5., v o l . 15, pp. 168-170. (1920) The appendages, anatomy, and relationships.of t r i l o b i t e s ; Mem. Conn. Acad. Arts and S c i . , v o l . 7, 169 pp. Resser, C.E. (.1928) Cambrian f o s s i l s from the . . Mojave Desert; Smithsonian Misc. C o l l . , vol.. 81, no. 2, pp.. 1-14. (1936) Second contribution to nomenclature of trilobites;.Smithsonian Misc. C o l l . , v o l . 95, no. 4, pp. 6-11. 54. Resser, C.E. (1938) Cambrian System of the southern Appalachians; Geol. Soc. Amer'., spec, paper no. 15, 140 pp. Resser, C.E., and Howell, B.F. (1938) Lower Cambrian Olenellus zone of. the Appalachians; B u l l . Geol. Soc. Amer., v o l . 49, pp". 195-248. Rice, H.M.A. (1937) Cranbrook Map-Area, B r i t i s h Columbia; Geol. Surv. Canada, Mem. 207. (1941) Nelson Map-Area, East Half, B r i t i s h Columbia; Geol. Surv. Canada, Mem. 228. Ross, R.J. (1948) Revisions i n the,terminology of t r i l o b l t e s ; Am. Jour. S c i . , v o l . 246, pp. 573-577. Schofield, S.J. (1915) Geology of Granbrook Map- Area, .Br i t i s h Columbia; Geol. Surv. Canada, Mem. 76. (1922)^ Relationship,of the, Pre- Cambrian (Beltian) t e r r a i n to the. Lower Cambrian Strata of,southeastern B r i t i s h Columbia; Geol. Surv. Canada, Mus. B u l l . no. 35* Stubblefield, C.J. (1936) Cephalic sutures and t h e i r bearing on current c l a s s i f i c a t i o n s of t r i l o b l t e s ; B i o l f . Rev., v o l . 11, pp. 1-30. Swinnerton, H.Hv (1915) Suggestions f o r a revised c l a s s i f i c a t i o n o f . t r i l o b l t e s ; Geol. Mag. Londy, v o l . 2, No;. 11, pp. 487-497; No. 12, pp. 538- . 545. (1919) The f a c i a l suture of the t r l l o b i t e ; Geol.. Mag. Lond., v o l . 11, no> 3, pp. 103-110. Twenhofel, W.H., and Shrock, R.R. (1935) Invertebrate Paleontology; McGraw-Hill. Waleott, CD. (1886) Second contribution to the studies on the Cambrian faunas of North America; U.S. Geol. Surv. B u l l . 30, pp.. 1-369. (1891) The fauna of the Lower Cambrian or Olenellus zone; U.S.-Geol. Surv., 10th Ann. Rept1., pp. .5H-658. (1910) Olenellus and other genera of the Mesonacidae; Smithsonian Misc. C o l l . , v o l . 53, No. 6, pp. 231-378. 55. Walcott, CD. A(19l6) Cambrian t r i l o b i t e s ; Smithsonian Misc.._Coll., v o l , 64, no. 3> pp. 157-258 B(1916) Cambrian t r i l o b i t e s ; Smithsonian. Misc..Coll., v o l . 64, no. 5, pp. 503-456. Walker, J.P. (1926) Geology and Mineral Deposits of „.Windermere Map-Area, B.C., Geol. Surv. Canada, Mem. 148. '• _ . Wanner, A. (1910) A new species of Olenellus from the Lower Cambrian of York County Pennsylvania; Wash. Acad. S c i . P r o c , v o l . 3 , pp. 267-272. 5 6 . PLATE I O l e n e l l u s eagerensls, n . sp. and 0. s c h o f i e l d l , n . s p . ' F i g s . 1 - 1 1 . 0 . ' eagere-nsis n . sp. (p. 3 7 ) 1* Specimen showing r e l a t i v e s i z e of thorax and base of 1 5 t h s p i n e . (Xl) Paratype. U . B . C , No. G T 1 0 2 . 2 . Holotype (XI) showing o c c i p i t a l and a x i a l s p i n e s . U . B . C , No. G T 1 0 1 . 3» 5 , ' 6 , 7 , 8, 9 v (Xl) Cephala showing narrow r i m , c h a r a c t e r i s t i c g l a b e l l a , and r i d g e to i n t e r g e n a l angle. Paratypes U . B . C , Nos. G T 1 0 3 , G T 1 0 5 - G T 1 0 9 . (Note: 8 i s a photograph.of a p l a s t e r c a s t . ) 4 . Incomplete specimen showing p o s t - o c u l a r mound » and character of pleurae'. (X2.3) Paratype, U . B . C , No". GT104. . . 1 0 . Minute cephalon showing t y p i c a l proportions 1 . ' ( X 5 ) Paratype. U . B . C , No;. G T 1 1 0 . . . 1 1 . Cephalon ( X 3 . 6 ) d o u b t f u l l y r e f e r r e d to t h i s s p e c i e s . _Note .expanded f r o n t a l lobev U . B . C , . No. GTlir. F i g s . 12-17. 0 !. schof i e l d l . n . sp'« (p. 40) 12, 15, 16, 17, (X1.7, • l'.5> 2, 2.6 r e s p e c t i v e l y ) o h a r a c t e r i s t i c cephala, showing v e i n i n g , r e l a t i v e l y s t r a i g h t p o s t e r i o r margin and short p a l p e b r a l lobesv Paratypes 1 . U . E . C . , Nos :. GT203 - GT206. 13'. Immature specimen p r e s e r v i n g i n t e r g e n a l and a x i a l s p i n e s . (X2.5) U . B . C . No> GT202. 14'. Holotype (X2.1) showing narrow r i m and a x i s , strong p o s t - o c u l a r node, short p a l p e b r a l l o b e , and veining' . U . B . C , No. GT20I. PLATE I 57. PLATE II Paedeumias nevadensls. O l e n e l l u s c f . g i l b e r t i Wannerla walcottana and Bonnia c f . columbensis Paedeumias nevadensls (Waleott) F i g s . 1-5. (p. 44) 1. Two small complete specimens (X2.7) with spine on 15th segment and short i n t e r g e n a l s p i n e s . U . B . C . , No. GT301. 2. Very small specimen (X4.7) w i t h at l e a s t 10 t h o r a c i c segments. Note extremely strong i n t e r g e n a l spines, wide brim t r a v e r s e d by r i d g e and enlarged 3rd pleurae 1 . U . B . C , No'. GT302. 3. Elongated specimen (X4.1) with long 15th spine and 3rd pleuraef. Note wide r i m w i t h t r a c e of narrow epistomal p l a t e , and i n t e r g e n a l spines* reduced during growth. U . B . C . , No*. GT303. 5 r. Adult cephala (XI) showing r e d u c t i o n i n width of brim and. i n . development of i n t e r g e n a l s p i n e s . Nos. GT304, GT305'. O l e n e l l u s of . g i l b e r t l Meek F i g s . 6-10 (p. 35) F r o n t i s p i e c e . V e n t r a l cast of complete specimen (X4) showing asymmetrical - l ines p o s t e r o - l a t e r a l from eyes, broken epistomal p l a t e and structure of 15th s p i n e . U . E . C . , No. GT351. 6, 7* Complete s h i e l d and cephalon showing narrow b r i m , a x i a l and o c c i p i t a l spines'. U . B . C , Nos. GT352, GT353. 8 j; Specimen with broad rim and brim of intermediate width ( X I ) . U . B . C No. M i l . (Dorsal mold, photographed w i t h l i g h t from bottom r i g h t ) 9 . Cephalon with wider brim and narrower r i m than above^. U . B . C , No*. GT354. 10'. Wide-rimmed specimen showing s l i g h t Paedeumias - type r i d g e on b r i m . Note marks i n t e r p r e t e d as traces of antennules*. U . E ' . C , No'. GT355'* Wannerla walcottana (Wanner) F i g s . 11-18 (p':. 47) l l 1 . - 16'. Growth stages showing convexity and p r o p o r - t i o n s o f cephala, strong o c c i p i t a l r i n g , character PLATE I I •58, of r i m , and tendency of small specimens to c u r l up. Note mold of Paedeumias on 14.» U . B . C , Nos. GT501 - GT506. (Magnifications 3, 1, 1, 2.7, 4.3, 1, r e s p e c t i v e l y . ) 17*Flattened d o r s a l impression (X0.8) with a s s o - c i a t e d hypostoma and epistomal p l a t e . U . B . C , No. GT507. 18.Large hypostoma (XI) showing s t r i a t e d surface and apparent l a c k of d e n t i c u l a t i o r i . U . B . C , No. GT508. Bonnla c f columbensis Resser (p. 50) 19, 20. Pygidium and cranidium (X2.5) U . B . C , Nos. GT401, GT402. 4 8 0 O O ' 7 0 0 0 ' 6 0 0 0 ' _ 5 0 0 0 ' . 4 0 0 0 ' - 3 0 0 0 ' - 2 0 0 0 . IOOO'. Sea-level V CANADA D E P A R T M E N T OF M I N E S A N D R E S O U R C E S HON T.A.CRERAR. MINISTER, CHARLES CAM SELL. DEPUTY MINISTER M I N E S A N D G E O L O G Y B R A N C H JOHN McLEISH, DIRECTOR B U R E A U O F G E O L O G Y A N D T O P O G R A P H Y F.CC.LYNCH. CHIEF ISSUED 1938 12 116°o o' 4945'- L E G E N D O N o< z y o o o o o O o O </> z Li UJ S o o o N < M O D E R N R E C E N T A N D P L E I S T O C E N E 12 Glacial drift.; silt, sand, gravel. C R E T A C E O U S O R T E R T I A R Y II Granodiorite C A M B R I A N L O W E R C A M B R I A N IO EAGER FORMATION: argillite CRANBROOK FORMATION: qu.artz.Ue, magrvesite U P P E R P U R C E L L S E R I E S GATEWAY FORMATION': argillaceous quartxite, dotoniitic argillite., concretiortary and pisolitic dolomite L O W E R P U R C E L L S E R I E S PURCELL EXTRUSWES: andesitic lava PURCELL INTRUSIVES: diorite sills and dyke* z < DC CO < o UJ Ct CL 5 SIYKH FORMATION: highly coloured argillite and dclornitic argillile KITCHENER FORMATION: green, grey and purple, huff weathering, dolornitic. argdlite ('RESTON FORMATION green, purple and white, argillaceous quartxite ALDRIDGE FORMATION: grey, rusty weal?*/-* ui,, argillite arid argillaceous quartxite. FORT STEELE FORMATION: white quartxite, banded, grey argillite and quartxite, black., limy argillite, grey-green, dolornitic argdlite Drift, covered areas in which bedrock outcrops are tew or tacking Geological, boundary (located, approximate, assumed' Bedding (inclined. vertical, horixontal. overturned) fcxAJ.it (Ijocated, appro-innate. u.s-.v timed) — — . Glacial stride .' Geology by C.E.Cairnes. 1932; and HMA.Ricc.193S. 49 30 Contour interval IOO feet Elevations referred to Mean sea-level Height in feet 5 9 / 0 Prospect ; x Mine dump £ | ^ j l Surveyed and reproduced by tin- Hut-ran <>f flrulin/v and Topography. 125" izo" S , I 1,,<I, I., JIHI Ml/.:s

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