@prefix vivo: . @prefix edm: . @prefix ns0: . @prefix dcterms: . @prefix skos: . vivo:departmentOrSchool "Science, Faculty of"@en, "Earth, Ocean and Atmospheric Sciences, Department of"@en ; edm:dataProvider "DSpace"@en ; ns0:degreeCampus "UBCV"@en ; dcterms:creator "Kawase, Yoshio"@en ; dcterms:issued "2012-01-31T19:11:50Z"@en, "1956"@en ; vivo:relatedDegree "Master of Applied Science - MASc"@en ; ns0:degreeGrantor "University of British Columbia"@en ; dcterms:description """Archaeocyatha from the Lower Cambrian of Wolf Lake and Quiet Lake areas in the Yukon Territory are described and illustrated. The fossils occur in carbonate rocks and are well preserved. Much of the necessary structural detail of the fossils is clearly observed in thin-sections and on polished surfaces of the specimens. The collection contains twenty-three species, twelve of which are new species. The new species described are: Ajacicyathus yukonensis, Coscinocyathus multiporus. Coseinocyathus cassiariensis, Coscinocyathus inequivallug, Coscinocyathus serratus, Coscinocyathus veronicus, Coscinocyathus tubicornus, Carinacyathus perforatus, Pyenoidocyathus solidus, Loculicyathus elliptieus, Metacoscinus poolensis, and Claruscyathus ketzaensis. The genera Carinacyathus and Loculicyathus are reported for the first time in North America. The Yukon fauna is dominated by Coscinocyathidae and Pycnoidocyathidae, showing close relationship to faunae in the Cordilleran region of British Columbia. It also shows relationship to Siberian and Australian faunae. This fauna is very different from the archaeocyathid assemblages in Nevada and California, where the dominant forms are Ethmophyllidae and Ajacicyathiclae. Arehaeocyatha have been instrumental in determining the age of rocks underlying a large area of the Yukon Territory."""@en ; edm:aggregatedCHO "https://circle.library.ubc.ca/rest/handle/2429/40405?expand=metadata"@en ; skos:note "LOWER CAMBRIAN ARCHAEOCYATHA PROM THE YUKON TERRITORY by YOSHIO KAWASE B.A.Sc, U n i v e r s i t y of B r i t i s h Columbia, 195* 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 t o the standard required from candidates f o r the degree of MASTER OF APPLIED SCIENCE Members of the Department of GEOLOGY AND GEOGRAPHY THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1956 i ABSTRACT Archaeocyatha from the Lower Cambrian of Wolf Lake and Quiet Lake areas i n the Yukon T e r r i t o r y are described and i l l u s t r a t e d . The f o s s i l s occur i n carbonate rocks and are w e l l preserved. Much of the necessary s t r u c t u r a l de-t a i l of the f o s s i l s i s c l e a r l y observed i n t h i n - s e c t i o n s and on p o l i s h e d surfaces of the specimens. The c o l l e c t i o n contains twenty-three s p e c i e s , twelve of which are new speciesf. The new species described are: A j a c i c y a t h u s yukonensis, Coscinocyathus m u l t i p o r u s . Coseinocyathus c as s i a r i ens i s, Coscinocyathus i n e q u i v a l l u g , Coscinocyathus s e r r a t u s , Coscinocyathus v e r o n i c u s , Coscinocyathus t u b i c o r n u s , Carinacyathus p e r f o r a t u s , Pyenoidocyathus s o l i d u s , L o c u l i c y a t h u s e l l i p t i e u s , Metacoscinus p o o l e n s i s , and Claruscyathus k e t z a e n s i s . The genera Carinacyathus and Loculicyathus are reported f o r the f i r s t time i n North America. The Yukon fauna i s dominated by Coscinocyathidae and Pycnoidocyathidae, showing c l o s e r e l a t i o n s h i p t o faunae i n the C o r d i l l e r a n region of B r i t i s h Columbia. I t a l s o shows r e l a t i o n s h i p to S i b e r i a n and A u s t r a l i a n faunae. This fauna i s very d i f f e r e n t from the archaeocyathid assemblages i n Nevada and C a l i f o r n i a , where the dominant forms are Ethmophyllidae and A j a c i c y a t h i c l a e . Arehaeocyatha have been instru m e n t a l i n de t e r -mining the age of rocks u n d e r l y i n g a l a r g e area of the Yukon T e r r i t o r y . ACKNOWLEDGMENTS I wish t o express my s i n c e r e thanks t o Dr. V.J. O k u l i t c h , P r o f e s s o r and Chairman, D i v i s i o n of Geology, f o r h i s many suggestions and c o n s t r u c t i v e c r i t i c i s m s . I am indebted to him f o r h i s i n s t r u c t i o n s and help i n the prep a r a t i o n of i l l u s t r a t i o n s , and a l s o f o r h i s t r a n s l a t i o n of Russian p u b l i c a t i o n s . I wish to thank Dr. Aho, Dr. T r e t t i n , and the Geo l o g i c a l Survey of Canada f o r p r o v i d i n g the m a t e r i a l f o r t h i s t h e s i s . Mr. J.A. Donnan, g e o l o g i c a l t e c h n i c i a n , i n s t r u c t e d me i n the p r e p a r a t i o n of t h i n s e c t i o n s . Mr. J . McGraw a s s i s t e d i n the photography of pol i s h e d sections. F i n a l l y , I am g r a t e f u l t o my f e l l o w - s t u d e n t s , Mr. D.N. H i l l h o u s e and Mr. R.G. Greggs, f o r t h e i r help and d i s c u s s i o n i n the pr e p a r a t i o n of t h i s t h e s i s . LOWER CAMBRIAN ARCHAEOCYATHA FROM THE YUKON TERRITORY INTRODUCTION This t h e s i s i s based on a study of Lower Cambrian Archaeocyatha c o l l e c t e d by A. Aho and W. Padgham of the B r i t i s h Yukon E x p l o r a t i o n Company, and by W.H. Poole of the Geo l o g i c a l Survey of Canada i n the Yukon T e r r i t o r y . Through the courtesy of Aho and of the G e o l o g i c a l Survey of Canada, these c o l l e c t i o n s were made a v a i l a b l e f o r study. Another c o l l e c t i o n from the same area, k i n d l y presented by H. T r e t t i n , was examined but not studi e d i n d e t a i l . About twenty-four specimens were i n Aho's and Padgham's c o l l e c t i o n and over f i f t y i n the c o l l e c t i o n made by Poole. The f o s s i l s , which oecur In dark, f i n e - g r a i n e d carbonate r o c k s , were, f o r the most p a r t , w e l l preserved and r e l a t i v e l y l a r g e . T h e i r study was thus made e a s i e r . The present work c o n s i s t s mainly of d e t a i l e d de-s c r i p t i o n s and i d e n t i f i c a t i o n s of the specimens. The ever V p e r p l e x i n g problems on the causes of the e x p l o s i v e , world wide d i s t r i b u t i o n and the sudden disappearance of Archaeocyatha i n Cambrian time, and the s t u d i e s of ecology, ontogeny, or physiology are not discussed here. These problems have been de a l t w i t h elsewhere by Hinde, T a y l o r , V o l o g d i n , the Bedfords, Simon, O k u l i t c h , and other l e a d i n g p a l a e o n t o l o g i s t s . No attempt i s made i n t h i s t h e s i s to d i s c u s s the pros and cons of t h e i r t h e o r i e s and hypotheses. The g e n e r a l , b a s i c c h a r a c t e r i s t i c s of Archaeocyatha are given i n the f i r s t chapter of t h i s t h e s i s . In the second chapter the methods and c r i t e r i a used i n c l a s s i f y i n g the archaeocyathids are discussed. A l s o , the f o s s i l l o c a l i t i e s and the geology of the area are described b r i e f l y . The greater part of the t h e s i s , as stated e a r l i e r , concerns the systematic d e s c r i p t i o n of the archaeocyathids from the Yukon. In Chapter I I I , twenty-three s p e c i e s , of which twelve are new, are described. From the i n v e s t i g a t i o n of these f o s s i l s , conclusions are drawn i n the f i n a l chapter. O r i g i n a l l y , i t was hoped, by the study of these f o s s i l s , to e s t a b l i s h f a u n a l zones of the Lower Cambrian. This was found to be impossible because no data on the d e t a i l e d s t r a t i g r a p h y were a v a i l a b l e and because the f o s s i l s were not c o l l e c t e d i n a systematic manner. With d e t a i l e d s t r a t i g r a p h i c work i n conjunction w i t h systematic c o l l e c t i o n s of f o s s i l s , i t may be p o s s i b l e to set up archaeocyathid f a u n a l zones. This zoning, i f i t can be e s t a b l i s h e d , w i l l be i n v a l u a b l e i n r e s o l v i n g some of the above mentioned problems, such as phylogeny, of Arehaeocyatha. This s m a l l c o n t r i b u t i o n t o the p a l a e o n t o l o g i c a l s t u d i e s of Arehaeocyatha, i t i s hoped, w i l l be of value i n f u r t h e r s t u d i e s . CONTENTS Page ABSTRACT i ACKNOWLEDGMENTS . . . i i i INTRODUCTION ' i v Chapter I GENERAL CHARACTERISTICS OF THE ARCHAEOCYATHA I n t r o d u c t i o n 1 Morphology 3 A f f i n i t i e s 6 C l a s s i f i c a t i o n . . . 8 Chapter I I METHODS OF STUDY AND FOSSIL LOCALITIES I n t r o d u c t i o n 10 The Aho and Padgham C o l l e c t i o n 11 The G e o l o g i c a l Survey of Canada C o l l e c t i o n . . 13 P r e p a r a t i o n and Study of F o s s i l s 15 Chapter I I I SYSTEMATIC DESCRIPTIONS OF ARCHAEOCYATHA FROM THE YUKON TERRITORY Faunal L i s t 17 D e s c r i p t i o n of Species 18 A j a c i c y a t h i d a e . 18 Ajaeicyathus p u r c e l l e n s i s 19 A.jacicyathus yukonensis 20 Ethmophyllidae 23 Ethmocoscinus sp 23 Coscinocyathidae 25 Coscinocyathus dentocanis . . 25 Coscinocyathus multiporus 26 Coscinocyathus c a s s i a r i e n s i s 29 Coscinocyathus i n e q u i v a l l u s 31 Coscinocyathus s e r r a t u s 34 Coscinocyathus veronicus 36 Coscinocyathus tubicornus 38 Coscinocyathus sp 39 Carinacyathus p e r f o r a t u s . . . . 41 Page Arehaeocyathidae 45 Archaeocyathus c f . a t l a n t i c u s 45 Archaeocyathus (?) sp\" \". T~ 47 Pycnoidocyathidae 48 Pycnoidocyathus amourensis 48 Pycnoidocyathus columbianus 50 Pycnoidocyathus c f . o c c i d e n t a l i s 51 Pycnoidocyathus c f . d i s s e p i m e n t a l i s . . . . 54 Pycnoidocyathus s o l i d u s 55 Loculicyathus e l l i p t i c u s 58 Metacoscinidae 60 Metacoscinus poolensis 60 Metacoscinus sp 62 Claruscyathus Ketzaensis 64 Chapter IV SUMMARY AND CONCLUSION A f f i n i t i e s to Other Faunae 67 Age of the Rocks 68 Suggestions f o r Further Studies . 69 BIBLIOGRAPHY 71 EXPLANATION OF PLATES 75 ILLUSTRATIONS Figure Page, 1, O u t l i n e Map Showing World Wide D i s t r i b u t i o n of Archaeocyatha . . . . 2. Diagrammatic Sketch of a T y p i c a l Archaeocyathid Showing the Major S k e l e t a l Elements Table 1. Table of Formations P l a t e I . A j acicyathus p u r c e l l e n s i s , A.-|acicyathus yukonensis, Ethmocoscinus sp., Coscinocyathus dentocanis, Coscinocyathus m u l t i p o r u s , Coscinocyathus c a s s i a r i e n s i s Facing Page . . . . 75 I I . Coscinocyathus i n e q u i v a l l u s , Coscinocyathus s e r r a t u s , Coscinocyathus v e r o n l c u s , Coscinocyathus t u b i c o r n u s , ~\" Coscinocyathus sp. Facing Page . . . . 77 I I I . Carinacyathus p e r f o r a t u s , Archaeocyathus c f . a t l a n t i c u s , Archaeocyathus (?) sp.\" Facing Page . . . . 79 IV. Pycnoidocyathus amourensis, Pycnoidocyathus columbianus, Pycnoidocyathus c f . o c c i d e n t a l i s % Pycnoidocyathus c f . d i s s e p i m e n t a l i s , Pycnoidocyathus' s o l i d u s Facing Page . . . . 80 V. Loculicyathus e l l i p t i c u s , Metacoscinus p o o l e n s i s , Metacoscinus sp., Claruscyathus k e t z a e n s i s Facing Page . . . . 81 2 4 14 CHAPTER I GENERAL CHARACTERISTICS OF THE ARCHAEOCYATHA I n t r o d u c t i o n Archaeocyathids, now c l a s s i f i e d as an independent phylum Arehaeocyatha, i n the Sub-Kingdom Parazoa, were e x c l u s i v e l y Cambrian marine organisms w i t h world wide d i s t r i b u t i o n (Figure 1 ) . They i n h a b i t e d every Cambrian sea i n l a r g e numbers and i n extremely d i v e r s e forms i n d i -c a t i v e of an exp l o s i v e e v o l u t i o n . They l i v e d a s e s s i l e , benthonic l i f e on calcareous bottoms, forming i n some l o c a l i t i e s almost r e e f - l i k e s t r u c t u r e s . 2 F i g u r e 1, O u t l i n e Map Showing World Wide D i s t r i b u t i o n of Arehaeocyatha I t seems i n d i s p u t a b l e that archaeocyathids l i v e d i n great numbers i n shallow, r e l a t i v e l y c l e a r water zones p a r a l l e l t o the c o a s t l i n e s of the Cambrian seas. However, the e x t r a o r d i n a r y and robust development of t h i s phylum was s h o r t - l i v e d . Archaeocyathids apparently could not t o l e r a t e muddy-water con d i t i o n s nor defend them-selv e s against the encroachment of the algae. In North America and A u s t r a l i a , archaeocyathids became e x t i n c t , 3 l e a v i n g no recognizable descendants at the c l o s e of the Lower Cambrian. In E u r a s i a , Archaeocyatha may have con-tinued to the end of Middle Cambrian, but recent Russian reports by Zhuravleva seem to i n d i c a t e t h e i r e x t i n c t i o n at the c l o s e of the Lower Cambrian. Archaeocyatha made a sudden, c a t a s t r o p h i c disappearance. Morphology The d e l i c a t e and f r a g i l e skeletons of Archaeocyatha are composed of calcium carbonate but some, l i k e the A u s t r a l i a n specimens, are s i l i c i f i e d . S i z e and shape of skeletons are extremely v a r i a b l e . The shape of the skeletons v a r i e s from r e g u l a r c o n i c a l and c y l i n d r i c a l cups to f l a t , expanding saucer-shaped forms. In c r o s s - s e c t i o n , cups are q u i t e o f t e n e l l i p t i c a l w h i l e others are c r e n u l a t e d . Although great d i v e r s i t y i n form e x i s t s , the most t y p i c a l skeletons are goblet- or vase-shaped. In s i z e , skeletons may range from a few m i l l i -meters to over 50 centimeters i n diameter i n the f l a t expanding types, but the m a j o r i t y are l e s s than 30 m i l l i -meters i n diameter. U s u a l l y , only short fragments are c o l l e c t e d but Archaeocyatha may grow con s i d e r a b l y i n l e n g t h . Specimens of two or three f e e t i n l e n g t h w i t h diameters of four inches have been reported by B i l l i n g s . The more common, simpler type of Arehaeocyatha skeletons c o n s i s t s of an outer cup or cone and an inner cup so that the sk e l e t o n i s double w a l l e d (Figure 2 ) . The inner w a l l i s g e n e r a l l y c o n c e n t r i c w i t h the outer w a l l , but i t may be incomplete towards the apex or s p i t z area of the cone. The space between the w a l l s , c a l l e d the Central cavil y Outer j Inner wall Figure 2. Diagrammatic Sketch of a T y p i c a l Archaeocyathid Showing the \" Major S k e l e t a l Elements 5 i n t e r v a l l u m , i s occupied by s e v e r a l d i f f e r e n t s t r u c t u r a l elements which support the inner w a l l some d i s t a n c e away from the outer w a l l and a l s o subdivide the space i n t o compartments. These supports may be i n the form of s t r a i g h t , v e r t i c a l , r a d i a l p l a t e s c a l l e d p a r i e t i e s ; curved, i r r e g u l a r and anastomosing p a r i e t i e s or l^ a e n i a e ; and h o r i z o n t a l or arched t a b u l a r p l a t e s c a l l e d tabulae. These elements may be f u r t h e r complicated and strengthened by dissepiments, s y n a p t i c u l a e , c e l l u l a r or tubula r s t r u c t u r e s , and v e s i c u l a r t i s s u e s . In n e a r l y a l l cases, these s t r u c t u r a l elements and w a l l s are perforated by numerous pores and c a n a l - l i k e channels. The inner w a l l encloses the c e n t r a l c a v i t y which i s present i n most genera. The c e n t r a l c a v i t y , completely open upwards, was i n a l l p r o b a b i l i t y f r e e of l i v i n g t i s s u e though l i n e d by i t . In some genera, however, the lower parts of the c a v i t y i s occupied by i r r e g u l a r v e s i c u l a r t i s s u e s . Minor s t r u c t u r e s may o c c a s i o n a l l y p r o j e c t a short distance from the inner w a l l i n t o the c e n t r a l c a v i t y r e g i o n . On some specimens of Arehaeocyatha are preserved exothecal l a m e l l a e , whieh are i r r e g u l a r masses of t i s s u e , f i l a m e n t s , or f i b e r s attached to the outer s i d e of the s k e l e t a l cup. The exact nature and f u n c t i o n of these extran-eous, c a n c e r - l i k e growths are not f u l l y understood, but they may have, i n p a r t , served as h o l d - f a s t or anchoring 6 devices and as p r o t e c t i o n f o r the cup. A f f i n i t i e s Archaeoeyathid a f f i n i t i e s have been a c o n t r o v e r s i a l subject ever s i n c e B i l l i n g s described and named the f i r s t Archaeocyatha. They have been classed w i t h sponges, c o r a l s , protozoans, and calcareous algae. I n 1889, HInde, review-ing a l l archaeocyathids known at that time, disproved t h e i r a f f i n i t i e s w i t h the protozoans ( F o r a m i n i f e r a ) . L a t e r , Taylor ( 1 9 1 0 ) made h i s memorable c o n t r i b u t i o n to the knowledge of Archaeocyatha by p o i n t i n g out the absence of r e l a t i o n s h i p between them and algae. In subsequent ye a r s , Archaeocyatha were c l a s s i f i e d w i t h e i t h e r c o r a l s or sponges u n t i l O k u l i t c h ( 1 9 3 5 ) showed that Archaeocyatha do not belong w i t h c o r a l s but are a separate c l a s s of the phylum P o r i f e r a . R ecently, a c r i t i c a l reviewwas made by O k u l i t c h and De Laubenfels ( 1 9 5 3 ) as to the v a l i d i t y of t h i s separate c l a s s . Because they found that i t was impossible t o place the Archaeocyatha e i t h e r w i t h the phylum P o r i f e r a or w i t h any other de f i n e d major group of organisms, they erected a new phylum c a l l e d Archaeocyatha. Because archaeocyathids are s t i l l mistaken at times f o r sponges or s o l i t a r y c o r a l s , t h e i r main s i m i l a r i t i e s and 7 d i f f e r e n c e s w i l l be b r i e f l y discussed here. At a casual glance, archaeocyathids g r e a t l y resemble c o r a l s and sponges, e s p e c i a l l y i n s u p e r f i c i a l f e a t u r e s . The general c o n i c a l form and symmetrically arranged r a d i a l p a r i e t i e s of Areh-aeocyatha are s t r i k i n g l y s i m i l a r i n appearance to the s t r u c t u r e of s o l i t a r y c o r a l s , w h i l e the form, c e n t r a l c a v i t y , canal system, and p e r f o r a t e d s k e l e t o n are reminiscent of some present-day sponges. However, d i s s i m i l a r i t i e s of Arehaeocyatha from sponges and c o r a l s g r e a t l y outweigh these s u p e r f i c i a l resemblances. G k u l i t c h (1955a) has l i s t e d the e s s e n t i a l d i f f e r e n c e s as f o l l o w s : D i s s i m i l a r i t i e s from Corals (1) presence of porous inner w a l l ; (2) s o f t parts probably confined to i n t e r v a l l u m and p o s s i b l y a l i n i n g on outer and inner w a l l s , very u n l i k e anthozoan polyps; (3) l a c k of r e g u l a r i t y i n plan of the p a r i e t i e s , which may be increased or reduced i n haphazard manner; (4) s t r u c t u r e of p a r i e t i e s , i n d i c a t i n g l a c k of homology w i t h septa of c o r a l s ; (5) absence of p a r i e t i e s i n a l l n e p i o n i c skeletons ( s p i t z e s ) and i n some a d u l t i n d i v i d u a l s ; (6) n e a r l y constant width of the i n t e r v a l l u m ; (7) perforated nature of tabulae i n c o n t r a s t to imperforated tabulae of c o r a l s ; (8) wide d i s s i m i l a r i t y In form of many archeao-cyathids from c o r a l s ; and (9) geologic a n t i q u i t y of archaeocyathids and s e p a r a t i o n from o l d e s t known c o r a l s by a great time span. D i s s i m i l a r i t i e s from Sponges (1) sponges i n v a r i a b l y l a c k p a r i e t i e s and none have laminar outer and inner w a l l s such as are possessed by archaeocyathids; 8 although a few f o s s i l sponges seem to have s t i f f e n e d c l o a c a l w a l l s , these probably represent post-mortem a l t e r a t i o n ; although some sponges possess a c o r t e x , t h i s c o n s i s t s of s p i c u l e s which do not form a w a l l ; the g r a n u l a r - l a m e l l a r s k e l e t o n of archaeo-cyathids d i f f e r s g r e a t l y from the s p i c u l a r s k e l e t o n of sponges both i n mode of d e v e l -opment and general s t r u c t u r e ; the Archaeocyatha are confined t o Cambrian rocks, whereas the o l d e s t known calcareous sponges occur i n the Devonian; and i n archaeocyathids an i n i t i a l l y imperforate s p i t z gives r i s e to perforated w a l l s i n which i n c r e a s i n g s i z e of pores may leave only slender rods between them, but the sponge s k e l e t o n i s b u i l t up from somewhat wide l y separated n e e d l e - l i k e s p i c u l e s i n e a r l y ontogeny to a more or l e s s compact s t r u c t u r e of crowded s p i c u l e s i n mature growth. With c a r e f u l o b s e r v a t i o n , these d i f f e r e n c e s between archaeocyathids and sponges or c o r a l s can e a s i l y be detected. C l a s s i f i c a t i o n C l a s s i f i c a t i o n s of archaeocyathids have been pro-posed by Walcott (1886), T a y l o r ( 1 9 1 0 ) , O k u l i t c h ( 1 9 3 5 , 1943), Vologdin (1937, 1940), Bedford and Bedford (1939), and Simon ( 1 9 3 9 ) . The e a r l i e r proposed c l a s s i f i c a t i o n s are now disregarded. The c l a s s i f i c a t i o n adopted by O k u l i t c h , V o l o g d i n , and the Bedfords are b a s i c a l l y s i m i l a r . The l a t e s t c l a s s i f i c a t i o n of archaeocyathids has been proposed by (2) (3) (4) (5) (6) 9 O k u l i t c h (1955a)> which i s a modified v e r s i o n of h i s e a r l i e r (194-3) work. In t h i s t h e s i s , the c l a s s i f i c a t i o n proposed by O k u l i t c h ( 1955a) was s t r i c t l y adhered to i n order t o avoid confusing the already overloaded nomenclature w i t h i n v a l i d genus names. He has d i v i d e d Phylum Arehaeocyatha i n t o three classes - Monocyathea, Archaeocyathea, and Antho-cyathea - and has made systematic d e s c r i p t i o n s of a l l known genera of the c l a s s e s . He has a l s o given a f t e r each genus, i t s homonyms, synonyms, and type species w i t h i t s author and date of f i r s t p u b l i c a t i o n . CHAPTER I I METHODS OF STUDY AND FOSSIL LOCALITIES I n t r o d u c t i o n F o s s i l s of the two c o l l e c t i o n s s t u d i e d f o r t h i s t h e s i s came from a number of l o c a l i t i e s i n the Yukon T e r r i -t o r y . One c o l l e c t i o n was made by A. Aho and W. Padgham, and the other by W.H.Poole. Arehaeocyatha occur mainly i n dark carbonate rocks which are f i n e - g r a i n e d , massive to o o l i t i c i n t e x t u r e . Some specimens are p a r t i a l l y and a few completely weathered out from the lime m a t r i x . On the whole, the f o s s i l s are w e l l preserved, w i t h a few replaced by, c a l c i t e and a few fragmental because of the s l a t y nature of some limestone. Because the r e c o g n i t i o n of the d i f f e r e n t genera and species depends on the d e t a i l s of the s k e l e t o n , t h i n -s e c t i o n s and p o l i s h e d s e c t i o n s were made. Transverse and l o n g i t u d i n a l s e c t i o n s were cut of each specimen, and oblique s e c t i o n s were cut i n some. The a c i d etching technique, which can be a p p l i e d to s i l i c i f i e d specimens, could not be used f o r these specimens because of t h e i r calcareous nature. The Aho and Padgham C o l l e c t i o n In the summer of 1 9 5 5 , Aho and Padgham discovered Lower Cambrian f o s s i l s w h i l e doing d e t a i l e d mapping of the Kay Group mining claims f o r the B r i t i s h Yukon E x p l o r a t i o n Company. The claims s t r a d d l e the ridge which separates the head waters of White Creek and Ketza R i v e r i n the P e l l y Mountains i n the Quiet Lake Area (Department of Mines and Tech n i c a l Surveys, N a t i o n a l Topographic S e r i e s , Map Sheet 1 0 5 F ) , Whitehorse Mining D i s t r i c t , Yukon T e r r i t o r y . This area i s e a s i l y a c c e s s i b l e from two lakes on which planes can land: (a) Bruce Lake, from which t h i r t y miles of good t r a i l leads up Ketza R i v e r , and (b) G r a y l i n g Lake, from which i t i s a f i f t e e n m i l e hike up White Creek. The area can a l s o be reached i n two days by horse from the Canol Road, which runs i n a north-south d i r e c t i o n about t h i r t y miles t o the east. The exact f o s s i l l o c a l i t y ( l a t i t u d e 6 l ° 3 1 ' ; l o n g i -tude 1 3 2 ° 1 5 ' ) i s approximately 1000 f e e t northwest from the northwest corner of the Kay No. 31 c l a i m and on the t r a i l l e a d i n g to the Conwest camp which i s eight miles n o r t h e r l y from t h i s area. The l o c a l i t y i s marked on a map accompanying Aho's (1955) r e p o r t , \"Geologic Report on the Kay Group of Claims and Upper White Creek, Ketza River Area, Yukon T e r r i -t o r y \" , which was submitted t o the Department of Mines as assessment work. 12 Rocks of the Kay Group of claims and adjacent upper White Creek area, as reported by Aho, c o n s i s t c h i e f l y of marine sediments which have been f o l d e d , f a u l t e d , and weakly metamorphosed. P h y l l i t e , limestone, dolomite, and q u a r t z i t e are the main rock types. The Lower Cambrian rocks of limestone and p h y l l i t e are exposed along a N 7 0 ° W a n t i c l i n a l f o l d . The f o l l o w i n g s t r a t i g r a p h i c sequence of the area, i n descending order, i s reported by Aho: Apparent S t r a t i g r a p h i c S e c t i o n at Upper White Creek White, brown, and gray massive p y r i t i c q u a r t z i t e , minor greenish gray c h e r t , limestone and p h y l l i t e w i t h a n k e r i t e (?) impure q u a r t z i t e and gradations to l i m y s c h i s t s and minor green p h y l l i t e forming the bottom of t h i s s e c t i o n . Black p h y l l i t e or s l a t e (may c o n t a i n l o c a l s l a t y limestones) Massive to t h i n bedded'*, buff weathering dolomite w i t h l o c a l chert nodules and t h i n ribbon chert beds. Thin bedded s l a t y limestone and o o l i t i c limestone. L o c a l l y absent. Brown p h y l l i t e ( l o c a l l y limy) grading downward to gray and black p h y l l i t e . Blue-gray, massive f o s s i l i f e r o u s Lower Cambrian limestone ( l o c a l l y o v e r l a i n by 50 f e e t of brown p h y l l i t e ) . S e v e r a l beds of s l a t y or s h a l y limestone a l t e r n a t i n g w i t h g r a y i s h brown p h y l l i t e and grading downward i n t o gray p h y l l i t e at l e a s t s e v e r a l hundred feet t h i c k w i t h minor l i m y and sandy beds. Thickness S e v e r a l hundred feet 100 f e e t 100 t o 200 f e e t 50 f e e t ? 500 f e e t 150 to 200 f e e t 500 feet 13 Aho s t a t e s that the s e c t i o n holds f o r t h i s l o c a l -i t y , but does not preclude some degree of t h i c k e n i n g by t h r u s t i n g or i s o c l i n a l drag f o l d i n g , e s p e c i a l l y i n the i n -competent p h y l l i t e members. More r e g i o n a l geology of the area i s not known at the present time. The G e o l o g i c a l Survey of Canada C o l l e c t i o n During the f i e l d seasons of 1951 to 1954 i n c l u s i v e , W.H.Poole of the G e o l o g i c a l Survey of Canada mapped the Wolf Lake Area, Yukon T e r r i t o r y (Department of Mines and T e c h n i c a l Surveys, Sheet 105B; G e o l o g i c a l Survey of Canada P r e l i m i n a r y Map 55-21). With the c o n s t r u c t i o n of the A l a s k a Highway, t h i s area i s now r e a d i l y a c c e s s i b l e . Areas remote from the highway can be reached by s u i t a b l y equipped a i r c r a f t , which can land on any one of the numerous l a k e s . Pack horses can be used to great advantage anywhere i n the area. In the course of h i s f i e l d work, Poole c o l l e c t e d a number of Lower Cambrian f o s s i l s from d i f f e r e n t l o c a l i t i e s , which are marked on the P r e l i m i n a r y Map 55-21 of the Wolf Lake Area. F o s s i l s s t u d i e d f o r t h i s t h e s i s came from the f o l l o w i n g p l a c e s : (a) G e o l o g i c a l Survey of Canada c o l l e c t i p r t < n o s . 24035, 24040, and 24041; at latitude\\69y ° 0 3 ' , l o n g i t u d e 130°21\"; 3.0 miles S 30° E from Veronica Lake near milepost 702 A l a s k a High-way. F o s s i l s were c o l l e c t e d from Lord's Group C sediments, and (b) G e o l o g i c a l Survey of Canada c o l l e c t i o n no. 24036; at l a t i t u d e 60°12 ' 30\" , l o n g i t u d e 1 3 1 o l l ' 3 0 \" ; 1.0 m i l e due northeast from northeast end of Crescent Lake. F o s s i l s were c o l l e c t e d from Lord's Group B sediments. D e t a i l e d s t r a t i g r a p h y of the f o s s i l l o c a l i t i e s i s not immediately a v a i l a b l e , but Poole r e p o r t s that the f o s s i l s occur i n carbonate rocks of Lord's (1944) Group B and Group C sediments. Lord, doing e a r l i e r g e o l o g i c a l reconnaissance work i n t h i s area f o r the G e o l o g i c a l Survey of Canada, devised a t a b l e of formation shown i n Table 1. Era P e r i o d L i t h o l o g y Cenozoic T e r t i a r y ? B a s a l t Mesozoic J u r a s s i c or l a t e r G r a n i t e , g r a n o d i o r i t e , and a l l i e d rocks; u n d i f f e r e n t -i a t e d s c h i s t and gneiss P e r i d O t i t e and d u n i t e ; serpentine J u r a s s i c (?) Group D: t u f f , a n d e s i t e , agglomerate, a r g i l l i t e , and s c h i s t Palaeozoic C a r b o n i f e r -ous (?) Group C: limestone, dolomite, a r g i l l i t e , s l a t e , p h y l l i t e , q u a r t z i t e , and s c h i s t Palaeozoic (?) Group B: a r g i l l i t e , s l a t e , p h y l l i t e , c h e r t , q u a r t z i t e , arkose, conglomerate, and limestone Palaeozoic and/or Pre-Cambrian Group A: g n e i s s , s c h i s t , limestone, d o l o m i t e , quartz-i t e , and greenstone Table 1. Table of Formations 15 Lord (1944) s t a t e s that the age of the highly-a l t e r e d and metamorphosed s t r a t a of Group C i s unknown, as no f o s s i l s were found i n them. He reports that rocks i n Group B con t a i n f o s s i l s suggestive of c r i n o i d stems, and the r e f o r e considered to be Palaeozoic (?) i n age. In Group C were found f o s s i l s i d e n t i f i e d as Lophophyllum ? cascadenses Warren ? and Hapsiphyllum cacareforme ( H a l l ) ? and a cup c o r a l too poorly preserved to be i d e n t i f i e d . On p a l a e o n t o l o g i c a l evidence, Lord suggests Group C belongs to the Carboniferous (?) p e r i o d . I t i s reported by him that Group B and Group C d i f f e r l i t h o l o g i c a l l y , but t h e i r r e l a t i v e age r e l a t i o n s h i p i s unknown because they are separated by the Ca s s i a r B a t h o l i t h . P r e p a r a t i o n and Study of F o s s i l s Most of the specimens were i n d i v i d u a l fragments,, but a number which were imbedded i n limestone blocks were cut out w i t h a diamond saw. Transverse and l o n g i t u d i n a l t h i n - s e c t i o n s , u s u a l l y taken from the upper p a r t , were made f o r a l l specimens except the h i g h l y fragmental ones. P o l i s h e d s e c t i o n s were made from a l l specimens. The specimens were f i r s t cut w i t h the saw, then ground smooth on a s t e e l l a p w i t h carborundum as the a b r a s i v e , and f i n a l l y p o l i s h e d on a cloth-covered l a p . 16 Dimensions of the specimens were c a r e f u l l y measured, e s p e c i a l l y the t o t a l diameter, diameter of the c e n t r a l c a v i t y , and the width of the i n t e r v a l l u m . The number of p a r i e t i e s (when regular ) at the measured diameter were counted and the p e r f o r a t i o n arrangements of the s k e l e t o n were determined from examinations of t h i n - s e c t i o n s . The i n t e r v a l l u m c o e f f i c i e n t , that i s , the r a t i o of the width of the i n t e r v a l l u m i n m i l l i m e t e r s to the diameter of the c e n t r a l c a v i t y i n m i l l i m e t e r s , and the p a r i e t a l c o e f f i c i e n t -the r a t i o of number of p a r i e t i e s to the diameter at whieh the p a r i e t i e s were counted - were c a l c u l a t e d . These co-e f f i c i e n t s , along w i t h the nature of the inner and outer w a l l s and the i n t e r v a l l u m , were the main c r i t e r i a used t o c l a s s i f y the specimens. I t must be noted that the c o e f f i c i e n t s may be of d o u b t f u l value i n r a p i d l y expanding, i r r e g u l a r cups, i n which case, the general appearance becomes an important f a c t o r . Photographs of p o l i s h e d s e c t i o n s and n a t u r a l l y weathered out specimens were taken t o i l l u s t r a t e and supple-ment the w r i t t e n d e s c r i p t i o n s . Thin-sections were used as negatives and p i c t u r e s were p r i n t e d d i r e c t l y from them. CHAPTER I I I SYSTEMATIC DESCRIPTIONS OF ARCHAEOCYATHA FROM THE YUKON Faunal L i s t PHYLUM ARCHAEOCYATHA CLASS ARCHAEOCYATHEA ORDER AJACICYATHIDA Family A j a c i c y a t h i d a e Ajacicyathus p u r c e l l e n s i s O k u l i t c h A j a c i c y a t h u s yukonensis n. sp. Family Ethmophyllidae Ethmocoscinus sp. Family Coseinocyathidete Coscinocyathus dentocahis O k u l i t c h Coscinocyathus multiporus n. sp. Coscinocyathus c a s s i a r i e n s i s n. sp. Coscinocyathus i n e q u i v a l i u s n. sp. Coscinocyathus s e r r a t u s n. sp. Coscinocyathus veronicus n. sp. Coscinocyathus tubicornus n. sp. Coscinocyathus sp. Carinacyathus perfqratus n. sp. ORDER METACYATHIDA Family Archaeocyathidae Archaeocyathus c f . a t l a n t i c u s B i l l i n g s Archaeocyathus (?) sp. 18 Family Pycnoidocyathidae Pycnoidocyathus amourensis ( O k u l i t c h ) Pycnoidocyathus columbianus ( O k u l i t c h ) Pycnoidocyathus c f . o c c i d e n t a l i s ( O k u l i t c h ) Pcynoidocyathus c f . d i s s e p i m e n t a l i s ( O k u l i t c h ) Pycnoidocyathus s o l i d u s n. sp. Loculicyathus e l l i p t i c u s n. sp. Family Metacoscinidae Metacoscinus poolensls n. sp. Metacoscinus sp. Claruscyathus ketzaensis n. sp. The above l i s t i n c ludes archaeocyathids of both c o l l e c t i o n s . In the f o l l o w i n g d e s c r i p t i o n of s p e c i e s , f o s s i l s c o l l e c t e d by Aho and Padgham are designated by l e t t e r s \"AP\" and the specimen number. F o s s i l s from the Ge o l o g i c a l Survey of Canada c o l l e c t i o n are marked w i t h the l e t t e r \"Y\" preceded by a two d i g i t number and followed by the specimen number, f o r example, 35-Y-l. The f i r s t number i s taken from the l a s t two d i g i t s of the G e o l o g i c a l Survey of Canada c o l l e c t i o n number, 24035, and 1 i s the specimen number of that c o l l e c t i o n . D e s c r i p t i o n of Species Order AJACICYATHIDA Bedford and Bedford, 1939 Family A j a c i c y a t h i d a e Bedford and Bedford, 1939 19 A jacicyathus p u r c e l l e n s i s O k u l i t c h P l a t e I ; F i g . 1 Ajacicya t h u s p u r c e l l e n s i s O k u l i t c h , 1947 D e s c r i p t i o n General Shape and S i z e This i s a common species found i n the Lower Cam-b r i a n formations of the northern C o r d i l l e r a n r e g i o n . The specimens from the Wolf Lake Area, Yukon are short fragments of a form o r i g i n a l l y g e n t l y tapered and c o n i c a l w i t h a n a t u r a l l y e l l i p t i c a l c r o s s - s e c t i o n . The f o l l o w i n g are the average dimensions taken from four specimens: Diameter 2 5 mm. Diameter of c e n t r a l c a v i t y 16 mm. Width of i n t e r v a l l u m 6 mm. Number of p a r i e t i e s 73 Int e r v a l l u m c o e f f i c i e n t 0.38 P a r i e t a l c o e f f i c i e n t 2.92 Outer W a l l The outer w a l l i s t h i n , simple, and perforated by numerous f i n e pores, about 3 or 4 per i n t e r s e p t . I n t e r v a l l u m The medium wide i n t e r v a l l u m i s crossed by a moderate number of s t r a i g h t , r a d i a t i n g p a r i e t i e s . P a r i e t i e s , spaced about 1 mm. a p a r t , are t h i n , s imple, and per f o r a t e d by a number of small pores. Inner W a l l The inner w a l l appears simple and perfo r a t e d by pores, about 2 to 3 per i n t e r s e p t . In a l l specimens examined, 20 the inner wall and parts of the intervallum are replaced by c a l c i t e . Thus much of the pore arrangements are ob l i t e r a t e d . C o l l e c t i o n Geological Survey of Canada, c o l l e c t i o n no. 24035 Specimen nos. 35-Y-5» 6» 7 and 8 . Collected by W.H. Poole, 1 9 5 3 . Horizon and L o c a l i t y Lower Cambrian (Lord's Group C sediments); Wolf Lake Area, Yukon. Discussion The specimens of A.lacicyathus purcellensis Okulitch from the Yukon are almost i d e n t i c a l i n c h a r a c t e r i s t i c s to those found i n the Donald formation of the Dogtooth Mountains and i n the Upper Wolverine complex of Aiken Lake Area. No addition or amendments can be made to the o r i g i n a l description. A.lacicyathus yukonensis n. sp. Plate I ; F i g . 2 Description General Shape and Size Description of this species Is based on a single specimen from which a transverse thin-section was prepared, c and appears on the same glass s l i d e as Cos^nocyathus multiporus n. sp. It i s a r e l a t i v e l y small conical form which i s s l i g h t l y e l l i p t i c a l i n transverse section. 21 Diameter 7 -9 mm. Diameter of c e n t r a l c a v i t y . . . . 3 . 2 mm. Width of i n t e r v a l l u m 2 - 2 ^ mm. Number of p a r i e t i e s 17 I n t e r v a l l u m c o e f f i c i e n t 0 . 7 1 P a r i e t a l c o e f f i c i e n t 2 . 2 1 Outer Wall The outer w a l l i s t h i n , simple, and perforated by numerous s m a l l pores, up to s i x per i n t e r s e p t . The c l o s e l y spaced f i n e pores give the w a l l , i n c r o s s - s e c t i o n , a minute \" r i p p l y \" c h a i n - l i k e appearance. S t i r r u p pores are l o c a t e d along the i n t e r s e c t i o n of the p a r i e t i e s w i t h the outer w a l l . I n t e r v a l l u m The i n t e r v a l l u m i s r e l a t i v e l y wide and crossed by seventeen s t r a i g h t , r a d i a t i n g p a r i e t i e s of which two are s h o r t , incomplete, and i n t e r s t i t i a l . The p a r i e t i e s appear to be imperforated, but may have pores near the inner w a l l . Thickening of the p a r i e t i e s occurs where they j o i n the outer w a l l and a l s o s l i g h t t h i c k e n i n g occurs at the inner w a l l . Inner Wall The inner w a l l i s thickened and per f o r a t e d by pores i n a v e r t i c a l s e r i e s of about three per m i l l i m e t e r . S t i r r u p pores appear t o be present. C o l l e c t i o n G e o l o g i c a l Survey of Canada; c o l l e c t i o n no. 2 4 0 3 5 . Holotype i s specimen 35-Y-13 I-\". C o l l e c t e d by W.H.Poole, 1 9 5 3 . 22 Horizon and L o c a l i t y Lower Cambrian (Lord's Group C sediments), Wolf Lake Area, Yukon. D i s c u s s i o n The wid e l y spaced, almost imperforated p a r i e t i e s and the pore arrangements of the w a l l s resemble Archaeocy-a t h e l l u s . but the l a c k of d i s t i n c t f l u t i n g s or furrows of the outer w a l l opposite the p a r i e t i e s and the l a r g e r s i z e undoubtedly place t h i s specimen w i t h A.lacicyathus. The wide i n t e r v a l l u m r e g i o n and low p a r i e t a l c o e f f i c i e n t of t h i s species are u n l i k e any known A.lacicyathus except p o s s i b l y f o r the l a r g e r A.lacicyathus khemtschikensis ( V o l o g d i n ) , but they d i f f e r i n the form of the l o c u l i . The low p a r i e t a l c o e f f i c i e n t of A.lacicyathus yukonensis n. sp. may not be of s p e c i f i c importance because recent i n v e s t i g a t i o n s made by Zhuravleva (1955) on the growth stages of A.lacicyathus khemtschikensis (Vologdin) have revealed that at small d i a -meters, t h i s species has a very high p a r i e t a l c o e f f i c i e n t , but as the diameter i n c r e a s e s , the p a r i e t a l c o e f f i c i e n t de-creases a c c o r d i n g l y . At a diameter of 2.0 mm. the p a r i e t a l c o e f f i c i e n t was found to be 5»5» at 4 . 5 mm., 4.0, and at 5.0 mm., diameter at m a t u r i t y , the p a r i e t a l c o e f f i c i e n t was 3.0. From t h i s she concludes that the c o e f f i c i e n t becomes constant only when the organism has reached m a t u r i t y ; t h e r e -f o r e , i t i s not a r e l i a b l e c r i t e r i o n to use i n i d e n t i f y i n g t h i s species i n the adolescent stages. This statement i s worth no t i n g because i t may be a p p l i c a b l e to other species but was not s t u d i e d on A.lacicyathus yukonensis n. sp. The pore patterns and the appearance of the i n t e r v a l l u m of the l a t t e r are s u f f i c i e n t l y d i s t i n c t from other species to j u s t i f y the new s p e c i e s . Family Ethmophyllidae O k u l i t c h , 1943 Ethmocoscinus (?) sp. P l a t e I ; F i g . 3 D e s c r i p t i o n General Shape and S i z e A s i n g l e , s u b c y l i n d r i c a l f o s s i l fragment w i t h an e l l i p t i c a l c r o s s - s e c t i o n i s noted i n t h i s c o l l e c t i o n . I t i s about 45 mm. long w i t h the lower p o r t i o n m i s s i n g . Diameter 19-22 mm. Diameter of c e n t r a l c a v i t y 4 mm. Width of i n t e r v a l l u m 8-8£ mm. Number of p a r i e t i e s 35 Spacing of -tabulae 1-6 mm. I n t e r v a l l u m c o e f f i c i e n t 2-2^ P a r i e t a l c o e f f i c i e n t 1.7 Outer Wall The outer w a l l of t h i s specimen i s r e l a t i v e l y t h i c k and p e r f o r a t e d by l a r g e pores, about 1 or 2 per i n t e r -sept. I n t e r v a l l u m The very wide i n t e r v a l l u m region i s crossed by i r r e g u l a r p a r i e t i e s which are perfo r a t e d by l a r g e pores and thickened near the inner w a l l . The i n t e r v a l l u m i s f u r t h e r occupied by porous tabulae spaced at i r r e g u l a r i n t e r v a l s . Inner V a i l The Ethmophyllum-type inner w a l l i s the most c h a r a c t e r i s t i c f e a t u r e of t h i s specimen. The inner w a l l i s wide and perfo r a t e d by very coarse oblique canals. In transverse s e c t i o n , these oblique canals appear as 3 or 4 rows of v e s i c u l a r tubes l i n i n g the inner w a l l . C o l l e c t i o n Department of Geology, U n i v e r s i t y of B r i t i s h Columbia; specimen no. AP 7. C o l l e c t e d by Aho and Padgham, 1955. Horizon and L o c a l i t y Lower Cambrian limestones; P e l l y Mountains, Quiet Lake Area, Yukon. D i s c u s s i o n This specimen i s t e n t a t i v e l y placed i n the genus Ethmocoscinus because of the nature of the inner w a l l and the presence of tabulae i n the i n t e r v a l l u m . The very wide i n t e r v a l l u m and the much thickened, complicated v e s i c u l a r inner w a l l may warrant e r e c t i o n of a new genus, at l e a s t a new s p e c i e s , but u n t i l more specimens can be s t u d i e d to show that these c h a r a c t e r i s t i c s are d i s t i n c t and c o n s i s t e n t , such a c o n c l u s i o n would be premature. Family Coscinocyathidae T a y l o r , 1910 Coscinocyathus dentocanis O k u l i t c h P l a t e I ; F i g s . 4, 5 and 6 Coscinocyathus dentocanis O k u l i t c h , 1943 D e s c r i p t i o n This species i s very common i n the northern Cord-i l l e r a n province of North America and was f i r s t discovered i n the Dogtooth Range of P u r c e l l Mountains, B r i t i s h Columbia The o r i g i n a l d e s c r i p t i o n of the species by O k u l i t c h i s as f o l l o w s : The specimen i s a n a t u r a l l y weathered out l o n g i t u d i n a l s e c t i o n i n l i g h t - g r e y limestone. General Shape; Tubular, w i t h very s l i g h t t a p er. Reconstructed diameter must have been about 22 mm., and height about 60 or 70 mm., of which 50 mm. i s v i s i b l e . Width of i n t e r -vallum i s 5 mm. where diameter of c e n t r a l c a v i t y i s 12 mm., g i v i n g an i n t e r v a l l u m c o e f f i c i e n t of 5 mm. : 12 mm. Outer W a l l : Probably t h i n and simple. I n t e r v a l l u m : I n t e r v a l l u m i s crossed by r a d i a l v e r t i c a l p a r i e t i e s and s l i g h t l y convex upward tabulae. Resultant rectangular c e l l s or l o c u l i are about twice as high as wide; 14 p a r i e t i e s occur i n space of 1 cm., g i v i n g p a r i e t a l c o e f f i c i e n t of about 4 .5; tabulae are about 1 .5 mm. apart. Inner W a l l : Inner w a l l i s apparently smooth and simple, without any s t r u c t u r e s p r o j e c t i n g i n t o c e n t r a l c a v i t y . The specimens of t h i s c o l l e c t i o n agree c l o s e l y i n s p e c i f i c a t i o n s t o that of the o r i g i n a l except that the p a r i e t i e s may be s l i g h t l y t h i c k e r and fewer i n number at a 26 given diameter. The f o l l o w i n g measurements are the average taken from the present c o l l e c t i o n : Diameter 21-31 mm. Diameter of c e n t r a l c a v i t y . . . 11-19 mm. Width of i n t e r v a l l u m 5-7 mm. Number of p a r i e t i e s 90 Spacing of tabulae l£ mm. I n t e r v a l l u m c o e f f i c i e n t . . . . 0 . 4 P a r i e t a l c o e f f i c i e n t . 3 .46 The only a d d i t i o n which can be made to the o r i g i n a l d e s c r i p t i o n i s that Coscinocyathus dentocanis O k u l i t c h appears to be g e n e r a l l y e l l i p t i c a l i n c r o s s - s e c t i o n . The s m a l l d i f f e r e n c e s i n p a r i e t a l c o e f f i c i e n t are not considered to be of s p e c i f i c importance. C o l l e c t i o n G e o l o g i c a l Survey of Canada; c o l l e c t i o n nos. 24040 and 24041; specimen nos. 40-Y-4 and 611, and 41-Y-l. C o l l e c t e d by W.H. Poole, 1953. Horizon and L o c a l i t y Lower Cambrian (Lord's Group C sediments); Wolf Lake Area, Yukon. Coscinocyathus multiporus n. sp. P l a t e I ; F i g s . 7, 8 and 9 D e s c r i p t i o n General Shape and S i z e This species i s based on a s i n g l e l a r g e specimen which was 118 mm. long before i t was cut. The. specimen i s p a r t i a l l y weathered away, thus exposing a l o n g i t u d i n a l 27 s e c t i o n which shows numerous tabulae c r o s s i n g the i n t e r -vallum. The f o s s i l i s shaped l i k e a l a r g e t a p e r i n g cone. Dimensions, taken 35 mm* down from the l a r g e r end, are only-approximate estimations because of the incomplete nature of the cup due to weathering. Diameter . 38 mm. Diameter of e e n t r a l c a v i t y . . . 16 mm. Width of i n t e r v a l l u m - 10 mm. Number of p a r i e t i e s 100 Spacing of tabulae 1-2 mm. In t e r v a l l u m c o e f f i c i e n t . . . . 0.63 P a r i e t a l c o e f f i c i e n t 2.63 Outer Wall The outer w a l l appears to be t h i n , s i m p l e , and pe r f o r a t e d by numerous pores, about 2 t o 4 per i n t e r s e p t . I n t e r v a l l u m The i n t e r v a l l u m of the upper p o r t i o n of the specimen i s r e l a t i v e l y wide w i t h an i n t e r v a l l u m c o e f f i c i e n t of 0 .63, but i n the lower r e g i o n s , the i n t e r v a l l u m becomes extremely wide w i t h i t s r a t i o to the c e n t r a l c a v i t y equal to 7s4 or 1.75. I t i s crossed by very porous p a r i e t i e s and tabulae. The p a r i e t i e s , many of which are the s h o r t , i n t e r s t i t i a l type growing i n from the outer w a l l , are t h i n , s t r a i g h t , r a d i a t i n g , and perforated by extremely f i n e pores c l o s e l y spaced. In a random c r o s s - s e c t i o n of a p a r i e t y , 22 or more may be present. Tabulae, a l s o p e r f o r a t e d by a great number of f i n e pores which produce a s i e v e - l i k e appearance, are e s s e n t i a l l y h o r i z o n t a l and r e g u l a r i l y spaced about 1 to 2 mm. apart. Inner W a l l A s l i g h t l y o b l i q u e , l o n g i t u d i n a l t h i n s e c t i o n reveals c l e a r l y , the pore p a t t e r n of the inner w a l l . Large, o b l a t e , oval-shaped pores, which are as wide as the i n t e r -sept and occur, arranged i n a v e r t i c a l s e r i e s , 3 to 4 i n number w i t h i n the spacing of two tabulae, p e r f o r a t e the inner w a l l . The area of the v o i d i s , t h e r e f o r e , much greater than the area of the s o l i d . C o l l e c t i o n G e o l o g i c a l Survey of Canada; c o l l e c t i o n no. 2 4 0 3 5 . Holotype i s marked 3 5-Y - 1 3 I I C o l l e c t e d by W.H.Poole, 1 9 5 3 . Horizon and L o c a l i t y Lower Cambrian (Lord's Group C sediments); Wolf Lake Area, Yukon. D i s c u s s i o n The exceedingly numerous f i n e pores of the p a r i e t i e s and t a b u l a e , and the l a r g e pores of the inner w a l l are u n l i k e the porous nature of any p r e v i o u s l y described species. Because the s p i t z of t h i s specimen i s m i s s i n g , i t s nature i s not known, but the s m a l l e s t end present shows a very narrow c e n t r a l c a v i t y and a wide i n t e r v a l l u m crossed by very t h i c k and b i f u r c a t e d p a r i e t i e s . Coscinocyathus c a s s i a r i e s i s n. sp. P l a t e I ; F i g s . 1 0 , 1 1 , 12 and 13 D e s c r i p t i o n General Shape and S i z e These specimens, approximately 40 to 50 mm. In l e n g t h , are not complete archaeocyathids but are l o n g , t u b u l a r shaped fragments. They are e l l i p t i c a l i n c r o s s - s e c t i o n . Specimen no. 35-Y-7 i s taken as the holo-type w i t h dimensions as f o l l o w s : Diameter l5-20*jr mm. Diameter of c e n t r a l c a v i t y . . . 9-13 mm. Width of i n t e r v a l l u m 4 mm. Number of p a r i e t i e s 75 Spacing of tabulae 2 mm. or more In t e r v a l l u m c o e f f i c i e n t . . . . 0 . 3 6 P a r i e t a l c o e f f i c i e n t 4 . 1 5 The dimensions of no. 35-Y-9 are s l i g h t l y l a r g e r , but i t s c o e f f i c i e n t s are almost i d e n t i c a l w i t h those of the holotype. Although no. 35-Y-8 has a r e l a t i v e l y wide I n t e r v a l l u m , i t i s included i n t h i s group because i t i s s i m i l a r i n general appearance. Outer W a l l The outer w a l l i s not preserved; consequently, no accurate d e s c r i p t i o n can be given. I t i s p o s s i b l e that the w a l l was t h i n and simple. I n t e r v a l l u m The i n t e r v a l l u m i s crossed by numerous s t r a i g h t , r a d i a t i n g p a r i e t i e s and curved, n e t - l i k e tabulae. The 30 p a r i e t i e s may b i f u r c a t e , but are u s u a l l y r a d i a l , s t r a i g h t , and p e r f o r a t e d by many pores, up to ten i n a random c r o s s -s e c t i o n . The tabulae are arched, w i d e l y spaced, and per-f o r a t e d by many coarse pores which produce a s i e v e - l i k e t e x t u r e . The l o n g i t u d i n a l s e c t i o n of no. 3 5-Y - 7 , showing s t r u c t u r e s b e t t e r than the ot h e r s , i s not q u i t e p a r a l l e l to the c e n t r a l a x i s of the specimen. This f a c t , combined w i t h the f a c t that the tabulae are not h o r i z o n t a l but d i p p i n g , accentuates the curved, i r r e g u l a r appearance of the tabulae. Inner W a l l The inner w a l l i s s l i g h t l y thickened and perfo r a t e d by l a r g e pores, about one to two per i n t e r s e p t . I n v e r t i c a l d i r e c t i o n , they are spaced approximately 0 . 7 to 0 . 8 mm. apart. C o l l e c t i o n G e o l o g i c a l Survey of Canada; c o l l e c t i o n no. 2 4 0 3 5 . Holotype i s no. 3 5-Y - 7 ; paratypes are nos. 35-Y-8 and 9 . C o l l e c t e d by W.H.Poole, 1 9 5 3 . Horizon and L o c a l i t y Lower Cambrian (Lord's Group C sediments); Wolf Lake Area, Yukon. D i s c u s s i o n The porous nature, the t h i c k inner w a l l w i t h almost c a n a l - l i k e pores, and the i r r e g u l a r , curved tabulae of t h i s species d i s t i n g u i s h i t from other Coscinocyathus. Coscinocyathus l n e q u l v a l i u s n. sp P l a t e I I ; F i g s . 1 , 2 , 3 , 4 , 5 and 6 . D e s c r i p t i o n General Shape and S i z e D e s c r i p t i o n i s based on s i x l o n g , c y l i n d r i c a l shaped specimens of which the longest was 45 mm. before i t was cut. The outer w a l l shows weak, r e g u l a r , t r a n s -verse annulations or c o n s t r i c t i o n s where i t i s j o i n e d by the tabulae. Dimensions are as f o l l o w s : Outer W a l l The outer w a l l i s simple and appears to be per-f o r a t e d by l a r g e pores, but the pore p a t t e r n could not be determined. The w a l l i s s l i g h t l y c o n s t r i c t e d t r a n s v e r s a l l y at r e g u l a r i n t e r v a l s where i t i s jo i n e d by the tabulae. I n t e r v a l l u m The wide i n t e r v a l l u m r e g i o n i s crossed by p a r i e t i e s and tabulae. The p a r i e t i e s are t h i c k , s t r a i g h t , r a d i a t i n g , and perforated by small pores. Up to seven or e i g h t pores have been counted i n a random c r o s s - s e c t i o n of a p a r i e t y . A few p a r i e t i e s b i f u r c a t e towards the outer w a l l , and i n w e l l preserved specimens, they appear to extend a short 10-15 mm. 3-8 mm. 3£-5 mm. mm. distance i n t o the c e n t r a l c a v i t y . Very f i n e l y porous tabulae, which cross the i n t e r v a l l u m , are s l i g h t l y curved convex-upward, and are spaced about 1 to 2^ - mm. apart. The i n t e r s e c t i o n of tabulae w i t h p a r i e t i e s form rec t a n g u l a r l o c u l i of which the height, i n l o n g i t u d i n a l s e c t i o n , i s about 2 to 3 times the width. Inner W a l l L i k e the outer w a l l , the inner w a l l i s simple and perfor a t e d by l a r g e pores which appear t o be one per i n t e r -sept. However, p a r i e t i e s p r o j e c t a short distance from the inner w a l l i n t o the c e n t r a l c a v i t y , and i n t h i s r e -spect the inner w a l l d i f f e r s from the outer w a l l . C o l l e c t i o n Department of Geology, U n i v e r s i t y of B r i t i s h Columbia. No. AP-14 i s designated as the holotype; paratypes are nos. AP-13, 15, 16, 19, and 21. C o l l e c t e d by Aho and Padgham, 1955. Horizon and L o c a l i t y Lower Cambrian limestone from P e l l y Mountains, Quiet Lake Area, Yukon. D i s c u s s i o n The i n t e r v a l l u m and p a r i e t a l c o e f f i c i e n t s of t h i s species are almost i d e n t i c a l w i t h those of Coscinocyathus equivallum T a y l o r . They d i f f e r , however, i n that the pores of t h i s species are much coarser and that the p a r i e t i e s 33 p r o j e c t i n t o the c e n t r a l c a v i t y making the inner w a l l d i s s i m i l a r i n appearance to the outer w a l l , hence the name Coscinocyathus i n e q u i v a l l u s as opposed to CoscInocyathus equlvallum T a y l o r . The general appearance of Coscinocyathus i n e q u i v a l l u s n. sp. c l o s e l y resembles Coscinocyathus dentocanis O k u l i t c h , but i s much sm a l l e r . The width of the i n t e r v a l l u m t o the diameter of the c e n t r a l c a v i t y r a t i o i s much l a r g e r , and the p a r i e t i e s appear to be t h i c k e r i n t h i s s p e c i e s . O k u l i t c h (1948) has described a Coscinocyathus sp. from the Dogtooth Range of B r i t i s h Columbia as f o l l o w s : I t i s an a c u t e l y c o n i c a l fragment exposing a pleosponge i n a n a t u r a l l o n g i t u d i n a l s e c t i o n . The specimen i s e n t i r e l y r e c r y s t a l l i z e d and no d e t a i l s of i t s s t r u c t u r e , except a few upward arching tabulae, are v i s i b l e . The i n t e r v a l l u m c o e f f i c i e n t i s 4:6 or 0.6; the tabulae are spaced from l*js- mm. to 2 mm. apart. The t o t a l l e n g t h of the specimen i s 40 mm. and the maximum diameter i s 14 mm. An exposed p o r t i o n of the inner w a l l i n d i s t i n c t l y shows numerous, crowded, very f i n e pores. The outer w a l l i s worn smooth and does not show the pores. In one p o r t i o n of the specimen are f a i n t l y v i s i b l e t h i n s t r a i g h t p a r i e t i e s spaced about one-third of a m i l l i m e t e r apart. The poor p r e s e r v a t i o n of the specimen does not permit i t s s p e c i f i c determination beyond the f a c t that i t i s a Coscinocyathus w i t h elongated rect a n g u l a r l o c u l i . This d e s c r i p t i o n seems to f i t c l o s e l y , except p o s s i b l y f o r the inner w a l l , that of Coscinocyathus i n e q u i v a l l u s n. sp. U n t i l b e t t e r specimens can be found i n the Donald Formation of the Dogtooth Range, or other 34 l o c a l i t i e s , no d e f i n i t e c o n c l u s i o n can be made as to whether Coscinocyathus i n e q u i v a l l u s n. sp. i s a wid e l y d i s t r i b u t e d s p e c i e s . Coscinocyathus s e r r a t u s n. sp. P l a t e I I ; F i g s . 7 and 9 D e s c r i p t i o n General Shape and S i z e D e s c r i p t i o n i s based on a s i n g l e specimen, AP - 1 7 , which was about 50 mm. i n l e n g t h before i t was cut. I t i s a fragment of an acute c o n i c a l cup w i t h a s l i g h t l y e l l i p t i c a l c r o s s - s e c t i o n . The diameters of the lower, middle, and upper parts are 18, 2 3 , and 28 mm., r e s p e c t i v e l y . Weak, transverse annulations of the outer w a l l , s i m i l a r to those of Coscinocyathus i n e q u i v a l l u m n. sp., are present. Complete dimensions of the upper, middle, and lower p o r t i o n s are as f o l l o w s : Upper Middle Lower Diameter 28 mm. 23 mm. 18 mm. Diameter of c e n t r a l c a v i t y . . . . 15 mm. 10 mm. 8 mm. Width of i n t e r v a l l u m 7-8 mm. 7 mm. 5 mm. Number of p a r i e t i e s 105 80 70 Spacing of tabulae 3 -3£ mm. 3 - 3 ? mm. 3-3*r mm. In t e r v a l l u m c o e f f i c i e n t 0 . 5 0 . 7 0 . 6 3 P a r i e t a l c o e f f i c i e n t . . . . . . . 3 . 7 5 3 . 5 3 . 9 Outer W a l l Much of the outer w a l l has been replaced by c a l c i t e , but i t appears to be t h i n , s i m p l e , and pe r f o r a t e d by l a r g e 35 pores. Pore arrangement could not be determined. I n t e r v a l l u m The r e l a t i v e l y wide i n t e r v a l l u m r e g i o n i s crossed by a number of s t r a i g h t , r a d i a t i n g p a r i e t i e s which are per-f o r a t e d by a few small pores. An o c c a s i o n a l p a r i e t y may b i f u r c a t e . Up-arching t a b u l a e , p e r f o r a t e d by numerous sm a l l c i r c u l a r pores, crossed the i n t e r v a l l u m at r e l a t i v e l y w i d e l y spaced i n t e r v a l s . Inner W a l l The c h a r a c t e r i s t i c f e a t u r e of t h i s species i s i t s inner w a l l . In transverse s e c t i o n , the inner w a l l , i n p a r t , appears t h i n , s imple, and perforated by sm a l l pores, but i n greater p a r t , appears complicated by hoo k - l i k e s t r u c t u r e s p r o j e c t i n g i n t o the c e n t r a l c a v i t y . In l o n g i t u d i n a l s e c t i o n , the hooked elements give the inner w a l l a s e r r a t e d appear-ance. The inner w a l l s t r u c t u r e of t h i s species resembles that of Von T o l l ' s Archaeocyathus S i b l r i c u s and Taylor's Archaeocyathus W i r r i a l p e n s i s . G o l l e e t i o n Department of Geology, U n i v e r s i t y of B r i t i s h Columbia. Holotype i s specimen AP - 1 7 . C o l l e c t e d by Aho and Padgham, 1 9 5 5 . Horizon and L o c a l i t y Lower Cambrian limestone, P e l l y Mountains, Quiet Lake Area, Yukon. 36 D i s c u s s i o n S u p e r f i c i a l l y , t h i s species resembles Coscinocyathus i n e q u l v a l l u s n. sp. and Coscinocyathus dentocanis O k u l i t c h , but i t Is much l a r g e r than the former. I t s w i d e l y spaced tabulae and complicated inner w a l l d i s t i n g u i s h i t from p r e v i o u s l y described species. Coscinocyathus veronicus n. sp. P l a t e I I ; F i g . 8 D e s c r i p t i o n General Shape and S i z e The shape of t h i s s p e c i e s , judged from a fragment about 40 mm. l o n g , i s that of a gen t l y t a p e r i n g cone. In c r o s s - s e c t i o n , i t has an e l l i p t i c a l o u t l i n e . Diameter 2 0 - 3 0 mm. Diameter of c e n t r a l c a v i t y . . . . 1 2 - 2 1 mm. Width of i n t e r v a l l u m 5 mm. Number of p a r i e t i e s 110 Spacing of tabulae 1-1? mm. Int e r v a l l u m c o e f f i c i e n t . . . . . 0 . 2 9 P a r i e t a l c o e f f i c i e n t 4.4 Outer W a l l The outer w a l l appears to be t h i n and simple; the pore p a t t e r n i s not c l e a r l y v i s i b l e . I n t e r v a l l u m The narrow i n t e r v a l l u m region i s crossed by s t r a i g h t , r a d i a t i n g p a r i e t i e s and c l o s e l y spaced, f i n e l y porous tabulae. The p a r i e t i e s are perfo r a t e d by a few f i n e pores and thickened by secondary c a l c i t e . L o c u l i are r e c t a n g u l a r , s l i g h t l y higher than wide. Inner W a l l The inner w a l l , p e r f o r a t e d by r e l a t i v e l y l a r g e pores, appears to be very t h i n and simple. Because the specimen i s not w e l l preserved, the pore p a t t e r n could not be determined. C o l l e c t i o n G e o l o g i c a l Survey of Canada; c o l l e c t i o n nos. 24040 and 24041. Holotype i s marked 40-Y-2; paratypes are 41-Y-2 and 4. C o l l e c t e d by W.H.Poole, 1 9 5 3 . Horizon and L o c a l i t y Lower Cambrian (Lord's Group C sediments); Wolf Lake Area, Yukon. D i s c u s s i o n This species i s s i m i l a r i n p a r i e t a l c o e f f i c i e n t to Coscinocyathus dentocanis O k u l i t c h , but d i f f e r s i n the i n t e r v a l l u m c o e f f i c i e n t and i n the spacing of the tabulae. The almost quadrate l o c u l i of t h i s species resembles those of Coscinocyathus rhyacoensis O k u l i t c h and Coscinocyathus quadratus Bedford and Bedford, but the new species d i f f e r s from the l a t t e r two i n the c o e f f i c i e n t s . 38 Coscinocyathus tubicornus n. sp. P l a t e I I ; F i g s . 10 and 11. D e s c r i p t i o n General Shape and S i z e This species i s represented by a s i n g l e specimen, a s l i g h t l y curved t u b u l a r form p a r t i a l l y weathered out. I t s diameter decreases from 21 t o 12 mm, i n a l e n g t h of 60 mm. The lower p o r t i o n i s missing on t h i s specimen. I t i s r e -placed to some extent by c a l c i t e , which o b l i t e r a t e s the f i n e r d e t a i l s of the s k e l e t o n . Diameter 21-22 mm. Diameter of c e n t r a l c a v i t y . . . . 8-9 mm. Width of i n t e r v a l l u m . . . . . . . 6-7 mm. Number of p a r i e t i e s 80 Spacing of tabulae 1-^ -2 mm. In t e r v a l l u m c o e f f i c i e n t 0.77 P a r i e t a l c o e f f i c i e n t 3.81 Outer W a l l The outer w a l l appears t h i n and simple. The pore p a t t e r n cannot be determined from t h i s specimen. I n t e r v a l l u m The wide i n t e r v a l l u m i s crossed by p a r i e t i e s and tabulae. The p a r i e t i e s are t h i n , s t r a i g h t , r a d i a t i n g , and per f o r a t e d by numerous f i n e pores. Tabulae, spaced about l£ t o 2 mm. ap a r t , are porous mesh-like and s l i g h t l y arched convex-upward. Inner W a l l The inner w a l l i s very t h i n , simple, and per f o r a t e d by p o s s i b l y two pores per i n t e r s e p t . The exact pore 39 arrangement of the inner w a l l i s not known. In p a r t , the w a l l appears to be invaded and pushed i n by f o r e i g n m a t e r i a l , causing the p a r i e t i e s to p r o j e c t s l i g h t l y i n t o the c e n t r a l c a v i t y . C o l l e c t i o n G e o l o g i c a l Survey of Canada; c o l l e c t i o n no. 24036. Holotype i s marked 3 6 - Y - l l . C o l l e c t e d by W.H. Poole, 1 9 5 3 . Horizon and L o c a l i t y Lower Cambrian (Lord's Group B sediments); Wolf Lake Area, Yukon. D i s c u s s i o n The t h i n , simple, r a d i a t i n g p a r i e t i e s and c l o s e l y set tabulae of t h i s specimen place i t i n the genus Coscinocyathus. However, the wide i n t e r v a l l u m , the narrow c e n t r a l c a v i t y , and i n the main, the general appearance of t h i s species are qu i t e d i f f e r e n t from those of the other s p e c i e s . Coscinocyathus c y l i n d r i c u s Boremann and Coscin ocyathus tuba Bornemann a l s o have a wide i n t e r v a l l u m , but i n general appearance, t h i s new species i s q u i t e unique. Coscinocyathus sp. P l a t e I I ; F i g . 12 D e s c r i p t i o n General Shape and S i z e This species i s represented by a very short f r a g -40 ment of a long c y l i n d r i c a l form. Because i t s general appearance i s not known and much of the f o s s i l i s replaced by e a l c i t e , a s p e c i f i c determination can not be made. Diameter . . . . . 25-32 mm. Diameter of c e n t r a l c a v i t y . . . . 15 mm. Width of i n t e r v a l l u m 5-9 mm. Number of p a r i e t i e s . . . . . . . . 106 Spacing of tabulae 1-1?^ mm. In t e r v a l l u m c o e f f i c i e n t 0.4? P a r i e t a l c o e f f i c i e n t 3.72 Outer W a l l The outer w a l l i s a simple t h i n mesh, perforated by f i n e pores. I n t e r v a l l u m Extremely t h i n , r a d i a t i n g p a r i e t i e s p e r f o r a t e d by very f i n e pores, and f l a t , c l o s e l y spaced, n e t - l i k e tabulae cross the i n t e r v a l l u m r e g i o n . Inner Wall The inner w a l l appears very t h i n and p o s s i b l y per-f o r a t e d by numerous f i n e pores. C o l l e c t i o n G e o l o g i c a l Survey of Canada; c o l l e c t i o n no. 24036. Specimen i s marked 36-Y-10. C o l l e c t e d by W.H.Poole, 1953. Horizon and L o c a l i t y Lower Cambrian (Lord's Group B sediments); Wolf Lake Area, Yukon. D i s c u s s i o n The general appearance and the s a l i e n t features 41 can not be determined on t h i s s m a l l fragment, but the very t h i n and d e l i c a t e nature of the w a l l s and s k e l e t a l elements i s the s t r i k i n g c h a r a c t e r i s t i c . The fineness of the s k e l e t o n resembles that of Coscinocyathus tubicornus n. sp. but i t d i f f e r s i n i n t e r v a l l u m c o e f f i c i e n t . I f other specimens of the former can be found to show that l a r g e r diameters give smaller i n t e r v a l l u m c o e f f i c i e n t s , then the specimen under c o n s i d e r a t i o n could c e r t a i n l y be c l a s s i f i e d as Coscinocyathus tubicornus n. sp. The c o e f f i c i e n t s of t h i s specimen are s i m i l a r to those of Coscinocyathus dentocanis O k u l i t c h , but i n general appearance there seems to be no resemblance. Carinacyathus perforatus n. sp. P l a t e I I I ; F i g s . 1-5 D e s c r i p t i o n General Shape and S i z e N a t u r a l l y weathered out specimens of t h i s species were up to 110 mm. long and t u b u l a r i n shape before they were cut. In c r o s s - s e c t i o n , they are e l l i p t i c a l . Specimen 35-Y-12, being the best preserved, was chosen as the holotype. 42 Diameter 2 1 - 3 5 mm. Diameter of c e n t r a l c a v i t y . . . . 16 mm. Width of i n t e r v a l l u m . . 4-8 mm. Number of p a r i e t i e s . 100 Spacing of tabulae l ^ - 2 j | mm. In t e r v a l l u m c o e f f i c i e n t 0 . 3 8 P a r i e t a l c o e f f i c i e n t 3 . 5 7 Outer W a l l The outer w a l l i s not w e l l preserved, but appears to be t h i n , s imple, and perfo r a t e d by numerous sm a l l pores. The pore p a t t e r n i s not known. In t e r v a l l u m The i n t e r v a l l u m i s crossed by numerous s t r a i g h t , r a d i a t i n g p a r i e t i e s and by weakly up-arched tabulae. The p a r i e t i e s , spaced about 0 . 8 mm. a p a r t , are p e r f o r a t e d , i n a random c r o s s - s e c t i o n , by twelve or more very f i n e pores about 0.1 mm. i n diameter. The t a b u l a e , spaced l£ t o 2-jj? mm. apar t , are perfo r a t e d by numerous f i n e pores, r e s u l t i n g i n a f i n e meshed net. The i n t e r s e c t i o n of tabulae w i t h p a r i e t i e s form rectangular l o c u l i , which are about twice as high as they are wide. Inner W a l l The most c h a r a c t e r i s t i c f e a t u r e of t h i s species i s i t s inner w a l l . I t i s composed of continuous annular, s i g m o i d a l l y curved p l a t e s spaced about 0 . 5 mm. apart i n l o n g i t u d i n a l d i r e c t i o n . They p r o j e c t about 0 . 3 to 0.4 mm. i n t o the c e n t r a l c a v i t y and l i n e i t w i t h h o r i z o n t a l annular s h e l v e s . 43 C o l l e c t i o n G e o l o g i c a l Survey of Canada; c o l l e c t i o n no. 24035. Holotype i s no. 35-Y-12; paratypes are nos. 35-Y-6 and 10. C o l l e c t e d by W.H.Poole, 1953. Horizon and L o c a l i t y Lower Cambrian (Lord's Group C sediments); Wolf Lake Area, Yukon. D i s c u s s i o n These specimens, w i t h w e l l developed tabulae and s t r a i g h t , r a d i a t i n g p a r i e t i e s , undoubtedly belong to the f a m i l y Coscinocyathidae Taylor and are c l a s s i f i e d as genus Carin