The Early Silurian brachiopod Pentameroides from ...

The Early Silurian brachiopod Pentameroides from the Hudson Bay Lowlands, Ontario JIN JISUO Department of Geological Sciences, University c$ Saskutchewart, Saskutoon, Sask., Canada S7N OW0 AND

PAULCOPPER Department of Geology, Laurentian University, Sudbury, Ont., Catzadu P3E 2C6

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by Harbin Industrial University on 06/07/13 For personal use only.

Received November 19, 1985 Revision accepted March 25, 1986 Reexamination and serial sectioning of the type material of Reticularia septentrionulis Whiteaves 1904 and Meristinu expansa Whiteaves 1904, from the Silurian (upper Llandovery) Attawapiskat Formation, Ekwan River, Hudson Bay Lowlands, indicate that they belong to the same species and that they can be assigned to the genus Pentameroides. These described species are also identical to Sapelnikovia [=Reveroides] norJordi Boucot and Johnson 1979, from the same formation on the Attawapiskat River nearby. All three species are thereby assigned to a single species, Pentameroides septentrionalis. The inflated shell of this species mnges from smooth and nonlobate to bisulcate-bilobate and rarely weakly trisulcate. This morphology is thereby viewed as a species-specific chardcter, leading to the conclusion that Reveroides Sapelnikov 1976 is probably a junior synonym of Pentameroides. Une rkvision et une reconstitution par coupes sCrites des fossiles-types de Reticularia septentrionalis Whiteaves 1904 et de Meristina expansa Whiteaves 1904 provenant de la formation d'Attawapiskat du Silurien (LlandovCrien supkrieur) B Ekwan River, dans les basses-ten-es de la baie d7Hudson,indiquent qu'ils correspondent B une mGme espkce du genre Pentumeroides. Ces espkces dCcrites sont Cgalement identiques B Sapelnikovia [ = Reveroides ] no$ordi Boucot et Johnson 1979. et elles proviennent de la meme formation affleurant dans les environs de la rivikre Attawapiskat; par conskquent les trois fossiles appartiennent B la mCme espkce, Pentarneroides septentrionulis. La coquille gonflCe de cette espkce vane de lisse et sans lobe B bisillonnk -bilobCe et rarement trisillonnte, et cette morphologie est considCrCe cornme un caractkre propre B l'espkce, ce qui permet de conclure que Reveroides Sapelnikov 1976 est pmbablement un synonyme junior de Pentameroides. [Traduit par la revue] Can. J. Earth Sci. 23, 1309-1317 (1986)

Introduction Silurian shelly fossils were first noted from the Hudson Bay Lowlands 100 years ago by Bell (1886), who explored portions of the Attawapiskat and Albany rivers (Fig. 1). Bell's collections were tentatively identified by Whiteaves and assigned a Devonian age. Further collections were made from the Ekwan River by Dowling in 1901, and these were subsequently also identified or described by Whiteaves (1902, 1904, 1906). Savage and Van Tuyl (1919) developed the first stratigraphic scheme and made lists of fossils, including those of Bell and Whiteaves. This work was revised by Norris et al. (1968) during "Operation Winisk." Little further work has been done on Silurian fossils of the Hudson Bay Lowlands, with the exception of papers on nautiloids (Flower 1968), trilobites (Norford 1981), and conodonts (Lefevre et al. 1976), though it is clear that rich faunas remain to be described. During a revision of the pentamerid brachiopod faunas of Anticosti Island, the Hudson Bay specimens, identified by Whiteaves as spiriferids and athyrids, were reexamined and discovered to be pentamerids, necessitating this paper, which is an attempt to clarify the confusion in taxonomy. Silurian rocks in the Hudson Bay Lowlands are distributed as part of two separate sedimentary basins, the Hudson Bay Basin to the north and west and the Moose River Basin to the southeast, divided by the Cape Henrietta Maria Arch. The three species in question come from the northern part of the Moose River basin, from outcrops along the Ekwan and Attawapiskat rivers (Fig. 1). Unlike the Silurian succession in the Michigan Basin, carbonates of the Hudson Bay Lowlands are generally limestones and not dolomites. Reef development is known in the Attawapiskat Formation, most of which is apparently of late Llandovery age, with perhaps only the upper few metres Printed in Canada / 1rnprin-d au Canada

being of early Wenlock age (conodont data in Lefevre et al. 1976). The brachiopods examined appear to have been collected from thinly bedded limestones at or near the base of the Attawapiskat Formation, though it is impossible to verify this at present with the limited lithological and stratigraphic information provided by Whiteaves (1902, 1904, 1906). According to Lefevre et al. (1976), the upper part of the Attawapiskat Formation is anhydrite and gypsum rich, an unsuitable environment for brachiopods . Norford (198 1) identified Pentameroides from the lower part of the Attawapiskat Formation in well cores. According to Lefevre et al. (1976), brachiopods are also common in their unit VIIIa, which they assigned to the underlying Ekwan Formation. Pentameroides is a common genus in Early Silurian rocks of North America. McChesney (1861) described the first species of the genus, P. bisinuatus from Wisconsin. Schuchert and Cooper (1931) established the genus Pentameroides, based on the subspecies Pentamerus oblongus subrectus Hall and Clarke 1893, from the late Llandovery Hopkinton Dolomite of Jones County, Iowa. They diagnosed it as having a cruralium in the brachial valve. Later, Amsden (1953) studied the internal structure of this species by means of serial sectioning and noted that Pen~ameroides was characterized by a fourfold brachial apparatus (inner plates, brachial processes, outer plates, and septal plates) in contrast to the threefold brachial apparatus of Pentamerus, which lacked septal plates. In his later work, Amsden (1964) rejected the existence of septal plates in Pentameroides, for he observed that the thick septal plates appeared to be separated from the thin outer plates only because of a differential secondary thickening. This interpretation of a threefold brachial apparatus in Pentameroides was followed by some later workers, and the brachial cruralium was believed to have evolved through a gradual convergence


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FIG. I . Sketch map of the Hudson Bay Lowlands showing the location of the collecting localities of Pentameroides septentpsionakis.(Whiteaves 1904). The stippled pattern indicates the outlines of Pdeozoic outcrop that define the Hudson Bay Lowlands. The limestone symbols mark the Middle Silurian (Wedock) and latest Elandovery age rocks. Dark circles mark the fossil occurrences (anow). The centre of the Moose River basin is capped by Early Cretaceous, lignite-bearing continental sediments.

of the outer plates of Bentamems (e. g ., Johnson 19'79). The concept of a four-element brachid apparatus, however, has persisted in Soviet literature; e. g., Sapelnikhsv (1961, 19'92, Fig. 48) noted that the septd plates were independent sf the outer plates not o d y in their secondary thickening but also in their lamellar layer. Serial sections of Pentameroides ~eptentrion&~iis @+%iteaves 1904), using acetobutymte peels, also c~nfk=mthat the bmchid apparabs (or cardinalia) was composed of four elements ( x p d plates, outer plates, bmchid processes, and inner plates) (Fig, 2; PI. 1, figs. 9 - 12). The lamellar layer of the septal plates is generally much thinner than that of the outer plates, and the well-presemed growth lines of the septd plates are closed at the junction with the outer plates, particularly at the anterior portion of the cardindia. A similar development was noted by us in specimens of Pepirtamcrokdes from the upper Jupiter Fornation of Anticosti Island. In Arnsden's (1964) illustmtion of the type species, Pentamemides subrectus, microscopic structure was not clearly shown. Further study may show that his interpretation of a fourfold brachial apparatus was correct. We believe that this may be a diagnostic character of the genus. It has k e n postulated that Pentamems evolved into Pentameroides through a griidual process of coalescence of the dis-

crete outer plates into a cmdiurn (St. Joseph 1948, p. 296; see ary of the Pentad s o Johnson (19'79) for a detailed su mems -Pentameroides lineage). This was later exploited as evidence for phyletic gradudism (Johnson and Colville 1982). The commonly discontinuous fine nature of the septal plates and outer plates, however, suggests that the formation of a c m d i u m in Pentameroides was, perhaps, not a simple union sf a pair sf discrete outer plates but an insertion of either septal plates or a new type of outer plate supported by septd plates. There is a lack of any fossil record for the detailed transition, suggesting that Pentamersides may just as readily have a p p e a ~ dvia rapid speciation in late Telychian time (C,).

Systernatie paleontology o m ~ Pentamerida a Schuchert and Cooper, 1931 FAMILY Pentame~daeM' Coy, 1844 SUBFAMILY Pentame~naeM' Coy, 1844 G E N U S Pentamemides Schuchert and Cooper, 1931 ( = ReIJeToides Sapelnikov 1976. = Sapelnikovia EkWcot and Johnson 19'99, 1981) Type species Pentamems oblongus var. subreetus H d l and Clarke, 1893, p. 248, Pl. 68, fig. 6; PI. 69, figs. 2-3, 8- 10, Jones County,

PLATE1 Pentacameroides septentrionalis (Whiteaves 1904). FIGS. 1- 8. Two specimens fmm the Attawapiskt River, Attawqiskat Fomation, okginally the sgmtyps of Meristim expansar Whiteaves. (1 -4) GS17731 c, showing a weakly pleated, faintly trilobate shell, x 1; (5 - 8) GS I773 Id, a smooth shell, x I. FIG. 8. Polished surface 0%serially sectioned specimen GS 1773 Hc (14.5 m from shell apex); note the fourfold cadinalia where the outer and inner plates disappear fmm view h sectioning, leaving behind the septal plates and brachial processes, x 3. FIG. 10. Enlarged view of fig. 9, xQ. FIG. 1 1 . Serial section peel photoEHlicmgmph (8.4 m from shell apex), showing (from bottom to top) the sepal phtes, outer plates (above the inflated junctions), bmchial processes (the two elliptical stmctures near top), and inner plates (only their dorsal portion), ~ 5 0FIG. . 12. Edarged view sf fig. I I , showing the function of septa1 plates with outer plates; note the self-enclosed growth lines of the septal plate, discontinuous from those of the outer plate; approximately x 150 (peel photographs from GS 17331 c ) .



CAN. J. EARTH SCI. VOL. 23, 1986

outer plates

-

( incl median septum )

1 brachial ao~aratus

FIG. 2. Detailed internal structure of the brachid valve of Pentameroides septeailfra'sgsalm'swhiteaves 1904). Drawings fmm a seAd section at 8,4 rm from shell apex to show the fourfold brachial apparatus. GS 17731c, from the Whiteaves collection, Attawapiskst River, Hudson Bay Lowlands, Attawapiskat Formation. Scale at right, x 20.

Iowa, HspEnton Dolomite, upper Llandoverian (Telychian), Silurian. Diagnosis Shell medium to Barge, transverse to elongate, biconvex, nodsbate to trilobate or bilobate -bisulcate, smooth to faintly plicate. Spondylium long, narrow, and deep, supported by a long and high median septum. Brachid cardindia long, cornposed sf four elements (septa1 plates; outer plates, which csdesce and may or may not be raised; brachial processes; and inner plates) (Fig. 2) (Amsden 1953; Johnson 1979; Boucot and Johnson 1979). Remarks Specimens here assigned to Pa septentrionals indicate that there is substantial variation in external shell mophology from smooth, nsdobate shells (Bl. 2, figs. 1- 10) to bilobate shells (Pl. 2, figs. 1 1- 15) to indications of trilabation (Pl. 1, figs. 1-4). Sapelnikov (1976), on the basis of Russian specimens (Weveroidesjolvemis), and Boucot and Johnson (1879), on the basis of examining specimens fmm the Attawapiskat Fomation of the Hudson Bay Lowlands (which they assigned to a new genus Sapelnikoi~ia,based on Pojslvensis), were sufficiently convinced that bilobation was a unique character thzt set aside their genera from n s m d Pentameroides. We have seen both bilobation and trilobation on silicified shells of Pmtamemides, albeit not as co only, from Manitoulin Island, where these occur in gre undance in the upper Fossil Hill Fornation, which is sf the s m e approximate age as the Amwapiskat Fo We believe that bibbation may n in some species than in sthers be a character more

and that lobation of the shell may have great infraspecific variability in collections from the same bed. It appears, furthemore, to have no stmtigmphic or geographic significance, because such variations appear to exist in widely separated regions and in rocks of the same age. The fou~elementbrachid apparztus is known from Pa,yeptentrisnalis whiteaves), from specimens described by Amsden (19@), and from Soviet literature (e .g ., Saplniksv 1961, 1872). Though other species need reexamination, it seems likely that this may have been a w i d e s p ~ a dfeature in Peatame~oidesand its probable synonym Revevoides ( =Sapelnikovia). However, it is not possible t s determine this in most dolomitized s r silicified species. Genus range Late Llandsveq (C,) - Wenlock, Silurian. Selected synonymy Reticularia septentrionalis Whiteaves, 1804, p. U F (no illustration). Me~istiaea(?)expansa Whiteaves, 1904, p. 45F [no illustration; the name septentrionalk is here given priority because it appears first in the descriptions]. Reticularia septent8.e^onalks (Witeaves) Whiteaves, 1986, p. 254, Pl. 27, figs. 2-5. r%g,ristina(?) expansa whiteaves) Whiteaves, 1906, pp. 245, 254, Pl. 27, figs. 6-7. Sapelnikovia norjiordk Boucot and Johnson, 1979, p* 1 19, Pl. 14, figs. 17- 19; Pl. 15, figs. 1 - 18. Type material Fifteen specimens originally collected by R. Bell in 1886 and D. B. Bowling in 1981. From Whiteaves' six original syntypes of R. septentrionalis collected by Bowling from the Ekwan River, GSUWa from the '%ver falls" is herewith selected as the leetotype. The remaining five syntypes are selected as padectotyps. These are GSUW, GSMWb, and GSMWc, also from the Ekwm River Fdls; GSMO1 (Pl. 3), from the "first rapid, E b a n River" (original label); and GSM02, fmm the mpid below fdls, '' There are nine original types s f M sexpansa. These include GS4-407 (the o d y specimen of e q a n s a labeled "holotype" in the Geological Survey of Canada catalogue and collected by Dswling from the "falls, Ekwan River, " which is probably the specimen from "partage road at fdls, Ekwan River, '' mentioned by Whiteaves (1904) ) and eight specimens, GS 1773l a -h, collected by Bell from the Athwapisht River (and suspected to be at or near the type locality of Sapelnikovia nofirdi Boucot and Johnson 1979). Type locality and type stratum The type specimens collected by Dswling were d l from the E k a n River and those collected by Bell fmm the Attawapiskt River, "seventeen to thirty miles below Rainy Island9' (N53"05" W84O23'; Witeaves (1904, p. 45F; 31906, p. 243) ). The restricted type locality he= selected is the Ekwan River Fdls, where the kctotype was collected (Fig. 1). The ~ ' no additional lithotypes were labeled "Upper S i l ~ r i a n ,with logic data. Recent work (Berry and Boucot 1970; Boucot and

PLATE2 Pendameroides septentric~naliswhiteaves 1904). The three oigikaal syntypes of Reticubria septcndrionalis Whiteaves fmm the Ekwan River Falls, Attawapiskat Formation, upper Elandovery, Telyehian, Silurian. FIGS.1-5. Tmnsveme shelf with a pointed pdicle umbs and lacking bzobation, here selected as the lectotype. G W W a , x 1. FIGS.6- 10. Large specimen with weak double S U ~ U S pamlectotype. , GSMWb, ~ 2 . FIGS.1 1- 15. Small shell with a broken pedicle umbs and distinct double sulcus or h m w , pardeetotype. GSMWc, x 2.


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turn

FIG.3. Serial sections of Penfamercsides sepfentrionail'swhiteaves 1904). es 1773lc, from the Attawapiskat River, Hudson Bay Lowlands, Amwapiskat Formation, x 5.

Johnson 1979) determined h a t the Attawagiskat Fornation in the Hudson Bay Lowlands is s f late Llandoveq (C3) to Wedock age. EeSvre e%al. 1976), on the basis s f csnodonts, assigned most of the Agawapiskat to the late Elandovery, with the upper few metres being assigned to the early Wedock. The type specimens probably c m e from the lower Attawapiskat Formation ( C 4 4 (Nonis et a&. (1968); Beny and Bsucot (1970) assigned an early late Llandovey, Cn-29age to the underlying Ekwan River Formation). The presence of Pentomerokdes suggests a C , - C , or younger age. Chow and Steam (1985) assigned a Middle Silurian age to the Attawapiskat Fornation.

Description Shell medium to large, transverse to slightly elongate, strongly biconvex or inflated, subpentagond to subcircular. Largest (impedest) specimen 52 rn long, 45 36 mdeep; average length 37.4 mm, width 38.2 m. thickness 26.2 m; length/wideh ratio 8.96. She11 surface smooth, usudly lacking teilobation and plications (except for faint indications of this in rare specimens, PI. 1 , figs. 1-4); shells either nodobate or having nanow, shdlow, median, anterior d y developed on both valves, varying from well defined to barely visible and producing bdobation on many shells. Hinge line short, curved. Pedicle umbo promi-

PLATE3 Bentameroides sepfe~atrionalk's (Whiteaves 1904). Four specimens from the Amwapiskat Formation, Telychian, Hudson Bay Lowlands. PIGS. E -4, Large shell with damaged anterior and weak furrow, from the "first rapid sf the Ekwan River," one of the six syntypes of Reticuhrba: sep$cratrionw&isWhiteaves, pamlectotype. GSUOH, X I . FIGS.5 -9. The original holotype by msaotypy of Merists'na epsansa Whiteaves 1904, "Ekwan River Falls." GSU0'9, x 1. FIGS. 10- 14. Well-preserved transverse shd2, one of h e eight syntypes of expansa collected by Bell from the Attawapiskat River. GS17731a, x 1. FIGS. 15- 19. Wider specimen with off-centre hmow OEBthe pdicle valve, also fmm Bell's collection. GS 1773I&, x 1.5.


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nent, being 4 - 8 m above the hinge line in relatively large specimens, with the beak incurved;-brachial umbo and beak

small. Internally, long, narrow, and deep spondylium with very thin walls, extending about two thirds of the shell length (Fig. 31, covered at its posterior end by a collar-shaped stmcture continuing anteriorly as the pseudodeltidkm. Spondylid median groove developed, Median septum thin and high, comng prismatic layer, posed of a median lamellar layer and fl its fine growth lines showing continuity with those of the shell, without a clear wedged-in type of junction. In the brachid valve, septd plates low but long, rising 2 mrn from the shell floor and extending approximately two thirds of the shell length, codescing dorsally to form the median septum. Outer plates low and much thinner &an the septd plates, having growth lines discordant with the sepM plates. Inner plates d s o thin, but two to three times higher than the outer plates, divergen? latedly at their posterior, becoming subparallel anteriorly. Inner and outer plates shorter than s e p d plates. Brachid processes delicate, rod-l&e, as long as the spondylium. Adductor muscle field not observed on the shell floor, probably uplifted by the c m d i u m , which shows a rnystest layer but no definable muscle scars. Wemrks Whiteaves (in Bell 1886, pp. 27 -28) initidly identified the fossils collected by Bell from the Atbwapiskat River as Devonian. Later, Whiteaves f 1904, 1906) described two new bmchiopod species, Wekicuiariba! septan~rionalk and Meristim(?) expesaam, based on Bell's 1886 collections and Dowling's -1901 collections from the Early Silurian Attawapiskt Formation of the Hudson Bay Lowlands. Whiteaves (1904, Pl. 27, fig. 7) pmvisionally assigned some of the specimens to RdicuJaria on the basis of what he believed to be, m d illustrated as, spiriferid micro-ornament, but which in fact is decorticated pentme6d shell. In the type specimens of both species, a median septum is dearly visible on the brachial, as well as pdicle, vdve. Serid sections of one s f the original Whiteaves specimens from the Amwapiskat River show that the long, n a m w , m d deep spondylium and c m d i u m are typical s f Pentameroddes. According to Whiteaves, Ms expansha differed from R. septentrionalis in its tmnsverse shell md a reduced pdicle umbs. These two features, however, vary ggsdationdly in the type specimens of the two species, and we cannot distinguish the collections despite excellent preservation and lack of diagenetic alteration. Therefore, Whiteaves' two species are here regarded as a single species, Pmtarneroides septen$rionalisPfirst descdbed in Whiteaves (ISM). Boucot and Jshnson (1979) established a new genus, Sap& nikovia, based on the species Pentameroides jolvensis Sapelnikov 1961, from the lower Wedock s f the central U d s Sespe&nikovia "differs from Pentamemides . in being bilobate9 (Boucot and Johnson 1979, p. B 19), i.e., it has a smooth shell with a median hmsw on each valve. They divided the smmth pentamerinids with "coalesced seater plates ' into two genera, tpilobate Pentamamides and bilobate Sagselnikovia, t h e ~ b yspecifying two distinct evolutionary lineages. Their new species, Sapelnikovia noflordi, was based on specimens fmm the Hudson Bay Lowlands (Attawapiskat River), apparenay without realization of the existence of the two species established by Whiteaves 80 years ago. In the type specimens of R septentkoaalis from the Ekwan and Attawapiskat rivers, shell bilobation (or bisulcation) varies from distinct to obscure.

Moreover, we have observed, in rich in $itu 6'nest9' accumulaaions of Pesatamems in life position fmm Anticosti Island, that shell lobation may be an infaspecifically variable character, d a diagand we thereby believe that it should not be ~ g a d e as nostic taxonomic criterion at the genus level (see M@rk(198 1) for further discussion). Pentamemides segstentrionaEis diffen from other known species in the genus by its strongly inflated biconvex shell, common development of a shallow median h m w on each vdve (a kind s f weak bilobation), and its c m d i u m supported by a low septum dong its whole length. Pentarneroidesjokvensis Sapelnikov 1961, Pngothla~dicusk k d e v 1892 ( i Bassett ~ 1977), and Po reversus Sapelnikov 1961 tend to have a cmwlium sessile at the posterior but supported by a low median septum anteriorly. Pentameroides reversus possesses a brachid valve equd to the pedicle vdve in length. Pentameroides jolvensis resembles bisin~atusMcChesney 1861 in its subtriangular outline, but no internal s t m c t u ~ sare known from Bf~inuatusfor cornpa~son.Bentameroides ed&actus Kulkov 1967 may be a junior synonym of jokvensis in its subtriangular shell and posteriorly sessile c m d i u m .

We thank Dr. T. E. BoItm for the lorn ofthe type specimens fmm the Geological Survey of Canada and Drs. Peter Sheehan and %.6. Johnson for their helphl review s f the manusc~pt. Research was generously supported by a N a t u d Sciences and Engineering Research Council of Canada gmnt to B. Copper. AMSDBN, T. W. 1953. Some notes on the Pen&mewcea, including a description of one new genus and one new subfamily. Journal of the Washington Academy of Sciences, 43(5), pp. 137- 247. 1964. Brachial plate structure in the bmchiopod family Pentameridtie. Palaeontology, '7, pp. 228 -239. BASSETT, M. @. 1977. The articulate bmchiopds fmm the Wedock Series of the Welsh Borderland and South Wales. Palaeontogwphical Society Monsgmphs, 4, gp. 1123 - 196. BELL,R, 1886. Report on an explsmtion of portions of the Attawapiskat and Albany rivers, Lonely Lake to James Bay. Geological Suwey of Canada, Annual Repa, HE(G), pp. 5 -38. BERRY,W. B. N., sand Boucs~,A. S. 1970. Cornlation of the North American Silurian mcks. Geological Society of America, Special Paper 102, pp. H -289, Bovco~,A. J . , and JOHNSON, J. @. 1949. Penbme4-inae (Silurian Bmchiqda). Pdaesntogmphica, l63(A), pp. 87 - 129, Pls. 1 - 15. 8 98 1. Emendations to the Pen&me~nae(Silurian Bmchiopda) . Souwad of Paleontology, 55411, p. 68 1. CHOW,A. M. C., and STEARN, C. W. 1985. Stratigraphy of the

Amwapiskat Formation along the Amwapiskat River. Geological Association of Cana&/Minewlogical Association of Canada, Prog m m e and Abstracts, p. AlO. F L ~ W ER. W H. , 1968. Silurian cephalogmds sf James Bay Lowland, with a revision of the family Nafiecocemtidae. Geological Survey of Canada, Bulletin 264, pp. 1-88. JOHNSON, M. E. 1979. Evolutionary bmchiopod lineages fmm the Llandovey Series of eastern Iowa. Pdaeontology, 22631, pp. 549-567, PI.67. JOHNSON, M. E., and COLVHELE, V. R. 1982. Regional integmtisn of evidence for evolution in h e Silurian Pentarnems --Pentamrt)ides linage. Eehaia, 85, pp. 4 1 -54. KULKOV, N. P. 8967- Shriian bmchiopods and stratigraphy sf the Alhi Mountains. Akademiya Nauk SSSR, Instiat geollogii i gmfizikii, 15 1 p., 2 1 plates. (In Russian.) LEBBDE~, N. 1892. BbenduH-ische Fauna der Timan. MCmoi~sdu ComitC g6010gique912(2), pp. 1-48.

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LEFfevRE, J., SAANAS, @. W.. and TIXIER, M. 1976. Palesecology of

Late Odovician and Early Silurian eonontsphorids, Hudson Bay Basin. Geological Assesciation of Canada, Special % 15, pp. 69-858. ~ C H E S N E Y , J. H. 1861. Descdptions sf fossils fmm the Pdaeoroic mcks of the western states. s o n s of the Chicago Academy of Sciences, BQ), pp. 7 7 - 9 5 , PL 9. M0RK, A. 1981. A reappraisal of the Lower Silurian brachiopods Bomabis and Pentameras. Palawntology, %I@), pp 539—553, Pls. 84-85. NORFORD, B. S. 1981. The trilohite fauna of the Silurian Attawapiskt Formation, wmthern Ontaris and no~ern Manitoba. Geological Survey of Canada, Bulletin 327, pp. 1-37. NORMS, A. W., SANFORB, B. V., and BELL, R. T. 1968. Geology of

the Hudson Bay Lowlands (Operation Winisk). Geological Survey of Canada, Paper 67-60, 118 p. SAPELNIKOV, V. P. 1961. Wenlock Pentameroides from the central Urals. Paleontologicheskii Zhurnal, 1, pp. 102-107, PL 3. (In Russian.) 1972. Silurian Pentameracea from the east side of the central and northern U d s , Tmdy instikt geologii i gmkhinii, Akademiya Nauk SSSR, 98, pap. 1-295, Pls. 1-57. 1 1976. Reveroides — a new Silurian genus of pentamerid from the eastern slopes of the Urals. Tmdy institut geologiii i

1 31'7

o f i m i i U d s k Naucbany Tsentm, p. 3. (In Russian.) SAVAGE, T. E . , and VAN TUYL, F. M. 1919. Geology md stratigraphy

of the % of aleszoic mcks in the vicinity of Hudson and lames bays. Bulletin of the Geological Society of Amfica, 3 pp. 339-378, PIS. 11-13. SCHUCHERT,

C,

and COOPER,

G,

A.

1931. Synopsis of the

brachiopod genera of the suboiders Orthoidea and Pentameroidea with notes on the Telotrcmata. American Journal of Science, 22(129), pp. 241-251. ST. JOSEPH, J. K. S. 1938. The Pentameracea of the Oslo region, being a description of the Kiaer collection sf penhmerids. Nonk Geologisk Tidsskrik, 1% pp. 225-336, Pls. 1 - 8 . WHITEAVES J. P. 1902. On the gems Trimerella, with descriptions of two supposed new species of that genus from the Silurian rocks of Keewatin. Ottawa Naturalist, 16(7), pp. 139-143, Pis. 2 - 3 . 1904. Preliminary list of fossils from the Silurian (Upper Silurian) cks of the Ekwan Ever, and Sutton Mill lakes, Keewatin, collected by D. B. Bowling in 1901, with descriptions of such species as appear to be new. Geological Survey of Canada, Annual Report, XIV(F), pp. 3 8 - 5 9 . 1906. The fossils of Silurian (Upper Silurian) rocks of Keewatin, Manitoba, the northeastern shore of Lake Winnipegosis, and the lower Saskatchewan River. Geological Survey of Canada, Palaeozoic Fossils, 3(4), pp. 243-298, Pis. 2 3 - 3 5 .