THE OCCURRENCE OF MISSISSIPPIAN BRACHlOPODS lN MICHIGAN Thesis for the Degree of M. S. MICHlGAN STATE COLLEGE Arlo Leigh Oden 1952 , WHMIHIHHHWHHI WW 29301013 7150 J This is to certifg that the / thesis entitled "The Occurrence of Mississippian Brachiopods in Michigan” presented by Arlo Le igh Oden has been accepted towards fulfillment of the requirements for L degree in M (jigggtg, L/f. KCZ£33L Major professor Thu: October 1, 1952 lulu “.13! ‘ll -_ - - . ’-T‘u PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES rotum on or bdoro date duo. * DATE DUE DATE DUE DATE DUE ' ”E‘ r w w - -_____—,_________..—————‘r_7 - = - = MSU Is An Nfirmotlvo Action/Equal Opportunity Insfituion ' ' W ulna-pd THE OCCURRENCE OF MISSISSIPPIAN BRACHIOPODS IN MICHIGAN By Arlo Leigh Oden A THESIS Submitted to the School of Graduate Studies of‘Michigan State College of Agriculture and Applied Science in.partia1 fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology and Geography 1952 THE‘QI; ERA 2?' VK‘ L” ACKNOWLEDGMENTS The writer wishes to acknowledge with thanks the help extended by Dr. William A. Kelly, who gave freely of his time, knowledge, and encouragement in the deveIOpment of this paper. Appreciation is also due to Dr. S. G, Bergquist, who has shown much interest in its progress. Thanks is also due to Dr. G. A. Cooper of the United States National Museum and Dr. G. M. Ehlers of the Museum of Paleontology of the University of Michigan for the loan of type specimens. To Mrs. J. E. Smith for editing and improving the text, many thanks are due. The writer is also greatly indebted.to Dr. B. T. Sandefur for his suggestions in the formulation of this thesis and help in the photography of the Specimens. WWW *‘X-iE-X-fl-fi-I {-381- o \f‘rxr- 4). EMS? ._‘." 3 fl) TABLE OF CONTENTS PAGE INTRODUCTION. .................. ........... . ....... .. ....... 1 THE OBJECTIVES OF STUDY................ .......... . ............... .. 2 mmwmmmmmms ..... . ........ . ................... . ...... .Hu 2 THE MISSISSIPPIAN STRATIGRAPHY OF MICHIGAN.. ....... . ...... ......... h cmwimHMEwNOFBmmeHmAH.H.H.H.. ..... n.n.u.n.n.n.u 8 CRITERIA USED FOR DESCRIBING AND NAMING BRACHIOPODA. ..... . 11 SYSTEMATIC DESCRIPTION OF BRACHIOPODA..... .............. ........... 13 DISCUSSION OF FAUNAL ASSEMBLACES........... ................. h3 CONCLUSIONS....... ...... SO BIBLIOGRAPHY...... ..... ..... ........ . ...... ...... ...... ....... ..... 51 INTRODUCTION The brachiOpods are usually gregarious in habit and live in a variety of environments, in general preferring well oxygenated shallow water. 0n the other hand, certain forms, such as Li ula, prefer the muddy bottoms. The brachiopod is a small, bivalved marine animal. The size of the individuals vary from the genus Composite, a few millimeters in width, to certain form of Spirifer and Syringothyris, which attain a width of 100 or more millimeters. BrachiOpods have inhabited the seas from the Lower Cambrian to the present day, attaining their maximum development in the Ordovician and Silurian. (Twenhofel and Shrock, 1935, p. 292) From these two periods alone, over three thousand species have been described. The wide verti- cal range and great diversity of the brachiOpods often limit their stratigraphic utility; However, due to their morphologic variation and slow migration they have, as 'I‘wenhofel and Shrock (1935, p. 297) point out, definite stratigraphic value: ISpreading slowly, brachiopods often attained very wide distribu- tion and for that reason are frequently valuable for correlation over wide areas." Great care was taken in noting the method and condition of preserva- tion of the brachiOpods so as to draw possible parallelisms with the fauna of adjoining states. MAP SHOWING THE DISTRIBUTION OF MISSISSIPPIAN ROCKS IN MICHIGAN _—..__. DOMINION OF CANADA [MEET 7‘}; V5,? 5‘ PRESOUE H —_ 4 ALCONA., Allc: lC3/A/V HP C A TA ISABELLA .SAAC3/fV/A SAGINAW OAKLANUD TON . .514 INGHAM lfV/AVV eneutLL- anaucu' , 'd. ‘ .7. . 0-. I.— tA BIIA ‘,tAss '" "Trout?- Map .I. THE OBJECTIVES OF STUDY The objectives of this study are twofold, and as follows: 1. To describe systematically and to identify the Mississippian brachiopoda of Michigan. 2. To describe, compare, and evaluate the occurrence of the Mississippian brachiOpods in Michigan with those in.0hio, Indiana, and Illinois so as to determine their stratigraphic value. SOURCES OF SPECIMENS The Mississippian brachiopods discussed in this thesis were obtained from the Goldwater, Lower Marshall, and Bayport formations in Michigan. The lowermost Mississippian formation is the t0p bed of the Antrim. According to Newcombe (1933, pp. h9), no brachi0pods are present in the Antrim; thus its discussion has been omitted from this paper. The sub-- surface nature of the Berea sandstone and Bedford formation prevents the collecting of samples and the obtaining of any reliable information about their age and faunal associations. Also no brachiOpods have been reported from the outcrops of the Michigan formation. Most of the Specimens examined have been collected over a number of years by members of the faculty and students of the Department of Geology at Michigan State College. Collections of the Bayport formation were centered in the "Thumb" area of Michigan. .Abundant specimens of the Bayport fauna were colleCted GENERALIZED COLUMNAR SECTION OF MICHIGAN MICHIGAN GEOLOGICAL SURVEY DIVISION SYSTEMSERIES FORMATION.GROUP LITHOLOGY THICKNESS ECONOMIC PRODUCTS , RECENT SAND.GRAVEL,CLAY,b Id . SAND. GRAVEL.PEAT. MARL. :LEISTOCENE GLACIAL DRIFT W, °“ "5 O-IOOO FRESH WATER PERMO-CARBONIFEROUS" “RED- BEDS" SHALE,CLAV, SANDV SHALEmsum GRAND RIVER SANDSTONE.sandy Shale 30 - 95 BUILDING SION£,FRESH WATER PENNSYLVAN'AN SAGINAw SHALE,SANDSTONE,IImeSIone,coa| 20-535 SQfiE-EEQL'FRES“ WATER- LIMESTONE. SANDY 0R CHERTY BAY PORT WESTONLSANDSTONE 2-I00 LIMESTONE.FRESH WATER MICHIGAN SHALE.jypsum,anhydnte.sandstone 0-500 GYPSUM ~MICHIGAN SIRAV" SANDSTONE 0-00 GAS _ FRESH WATER. BRINE MISSISSIPPIAN MARSHALL SANDSTONE.sandy ml. I00 400 BUILDING STONE COLDWATER SHALE.Sand5Ione.IImesIone 500 -I|00 SHALE. FRESH WATER SUNBURY SHALE O-I40 BEREA-BEDFORD SANDSTONE, SHALE 0-325 GAs.0IL ELLSWORTH - ANTRIM SHALE. IImeSIone IOO'950 SHALE.GA5 TRAVERSE LIMESTONE. SHALE I00- 800 fig’figffi'fitg'k GAS- BELL SHALE. LImesIone 0'80 SHALE ROGERS CITY-DUNDEE LIMESTONE 0-475 UMESTONE O'L'G‘S- DEVON'AN :FMEESSIOZITEDROLOMITE DETROIT RIVER 93L33LT5-"'"°3'°"°-5"' ISO-I400 0IL.GAS.S'ALI, DRINEf Y FRESH WATER SYLVANIA SANDSTONE.SANDY DOLOMITE 0-550 GLASS SAND. FRESH WATER BOIS BLANC DOLOMITE,CHERTY DOLOMITE 0-I000 BASS ISLAND DOLOMITE 50-570 DOLOMITE.FRESH WATER SALINA SALT. 00L0MITE, Shale.anhydnte 50-4000 SALT. GAS. OIL NIAGARAN S'LUR|AN Guelph- LocIl ort- Enpdme) DOLOMITE L , h I ”0-300 LIMESTONE DOLOWTE' Mamshque- um Bluff) - ""5"“ ” 0IL.GA5. FRESH WATER Cataract) CINCINNATIAN gamma)“ ) SHALE.LIMESTONE 250-800 ORDOV'C'AN ayw .- N OIL GAS LIMESTONE IRENTON-BLACA RIVER LIMESTONE. DOLOMITE zoo-I000 FRESH mm, . ST. PETER SANDSTONE 0 - I50 FRESH WATER OZARKIAN PRAIRIE DU CHIEN DOLOMITE.ShaIe 0-4I0 OR DOLOMIIE. SANDV DOLOMITE. - CANADIAN HERMANSVILLE Wm" I5 500 ‘ LAKE SU;ERIOR I m T N CAMBRIAN 3::333'.) SANDSTONE 500-2000 Egg-5°” 3,3,: ‘ (Cw Iormtms) We mm" SEMI-PRECIOUS GEM STONES IIILLARNEY GRANITE GRANITE. GNEISSJIorithycmtc ALGONK'AN HURON.“ SLAI£5.H£MAIITE. SCHIST. gm) aggroggm‘gém. ROAD METAL. BUILDING LAURENTIAN scmsr. GNEISS. GRANITE STONE.V£R0£ ANTIQUE. TALC. ARCHEAN GOLD AEEWATIN :93? 2%“"$*°"‘- ROAD MEIAL from the Bayport Quarry near Bayport, Michigan and from outcrOps in Arenac County. The same formation was sampled in Eaton County at the abandoned quarry near the city of Bellevue, Eaton County. Many of the type species of the Marshall formation originally had as their type localities the sandstone quarries of Marshall, Michigan, in Calhoun County. However, because of the abandonment and concealment Of these quarries all of the specimens examined in this study came from outcrOppings in the area from Point aux Barques to Willow Creek, near Huron City in Huron County. The Goldwater specimens were Obtained from either the area of Lighthouse Point in Huron County, or near Coldwater in Branch County. Fossils also have been studied from rock exposures in the vicinity of Rock Falls in Huron County. THE MISSISSIPPIAN STRATIGRAPHY OF MICHIGAN In 19h8, the Michigan Geological Society published a mimeographed paper entitled A Surmnary 93 the Stratigraphy 91 the Southern Peninsula 9}: Michigan by E. J. Baltrusaites, C. K. Clark, et a1. Parts of the dis- cussion pertaining to the Mississippian are reproduced below as background material necessary to this study. “The Antrim underlies the Southern Peninsula of Michigan from Charlevoix, Cheboygan, Montmorency, and Alpena Counties at the north, southward as far as Pulaski, Fulton, Whitely, and Allen Counties in northern Indiana; Paulding, Henry, and Lucas Counties in northwestern Ohio; and eastward under Kent, Lambton, Middlesex, and Elgin Counties in Ontario, Canada. The Antrim is essentially black carbonaceous shale with several thin, gray shale members in the lower part and is characterized by an abundance of Spore cases reported as Sporangites huronensis. It contains pyrite, dissemi- nated and in concretions, and large anthraconite concretions in various places. Apparently the.Antrim lies on the eroded Traverse limestone surface in the western and southwestern parts of the state, but elsewhere the contact appears to be conformable. The greenish gray Ellsworth shale of the western half of Michigan over- lying the black shale of the Antrim is contemporaneous with and interfingers with the upper Antrim.of central and eastern Michigan. The DevonianrMississippian boundary has been placed at different positions in the Antrim-Ellsworth sequence by various workers, but generally the upper part of the Antrim is considered.Mississippian in age. Further data are needed to establish the DevonianrMississ- ippian contact in Michigan. The Ellsworth is greenish gray dolomitic shale with Sporangites huronensis common near the zone of inter- fingering with.Antrim Shale. However, west of this area of inter- fingering, Sporangites are rare. As the Antrim and Ellsworth are known to be contemporaneous and the lower boundary of the Ellsworth is gradational with the Antrim, it is impossible at this time to give a maximum thickness of either of these formations. Together they have a thickness of 920 feet in northern Lake County and southernIdexford County, Michigan. The source of the Ellsworth sediments was very likely from the Wisconsin area, west of the Michigan.Basin. IThe Bedford and Berea cannot be satisfactorily subdivided in the subsurface. These rocks consist of gray shale, sandy shale, siltstone, and sandstone and lie conformably on the Antrim. From the BedfOrd-Berea pinch-out line approximately north and south near the center of the Southern Peninsula of Michigan, these sedi- ments thicken eastward at the rate of 100 feet in 25 miles to a maximun.thickness of 325 feet in northern Huron.County. The lower half of the section is essentially composed of gray shale and sandy shale; the upper half contains fine-grained sandstone and varying amounts of gray shale and siltstones. "The Sunbury is a black shale less carbonaceous than the Antrim. It overlies the Bedford-Berea, the Antrim, or the Ellsworth in different parts of the State. It pinches out in.Allegan, Barry, Kalamazoo, and St. Joseph Counties and is absent in Berrien, Cass, and Van Buren Counties, Michigan. The Sunbury extends a short distance into Steuben County of northeastern Indiana and‘Williams and Fulton Counties of northwestern Ohio. Over most of the central part of Michigan, the Sunbury rarely exceeds hO feet in thickness, but in eastern Michigan it thickens rapidly from approximately ho feet from a north-south line extending through Tuscola County to lhO feet in eastern.Huron.County along Lake Huron. "The Goldwater is blue to greenish gray shale with subordinate thin lenses and beds of dolomite, sandstone, and siltstone. It is from 500 to 1000 feet thick. In the central part of the Michigan Basin the average thickness is 1050 feet. The Goldwater shale is widely distributed in the southern part of the Southern Peninsula of Michigan from Otsego County southward into Indiana and Ohio. "This section of gray shale has several persistent beds which are easily recognized: near the base of the formation the "Goldwater Red Rock" unit is easily recognized over a large area and has more than one bed of red rock in the western part of the state. It grades from a non-calcareous shale to a shale having increasing amounts Of calcium carbonate and magnesium carbonate into crystalline limestone and dolomite, that ranges from a few feet to about 30 to hO feet in thickness. The shale above the "Red Rock" can be divided into two facies. In the western part of the Michigan Basin it is predominately gray shale with numerous beds of gray to brown dolomite which are very fossiliferous in places. The "Goldwater Lime," about 20 to 30 feet thick, an impure dolomite with a speckled or "salt" and "pepper" appearance, is one of the best recognized calcareous beds. It is well represented in the western and southwestern part of the State. The speckled appearance is due to darker colored grains of dolomite and grains of glauconite. Beds of gray to brown dolomite that grade to dolomitic shale are in the section. Brown sideritic material, which may be drilled up in concretions, is Observed in well cuttings and in large concretions in the outcrOp. The eastern facies is gray shale with subordinate amounts of siltstone and sandstone. The shale in the upper part of the formation is predominately red in colOr, which makes it practically impossible to determine the base of the overlying Marshall formation and suggests that the base of the Marshall is transitional with the upper Goldwater forma- tion. The red sandstone and siltstone are best represented in Huron, Genessee, Saginaw, and surrounding counties. nThe Marshall formation consists of gray to pink to red sand— stone that ranges from coarse grained to very fine grained sandstone and siltstone having high percentages of dolomite as cementing material. The thickness of the formation ranges from 100 to hOO feet; the average thickness is about 275 feet in the Central Basin area. The Marshall is in the central part of the Southern Peninsula and is absent in the northern and southern parts of the State due to non-deposition and erosion in the north and erosion in the south. It is the oldest Paleozoic formation entirely within the boundary Of'Michigan. "The lower part of the formation is characterized by sandstone commonly red in color. The sandstone, which is cemented with vary— ing amounts of dolomite, is very shaly and dolomitic near the base. In eastern Michigan, where it is difficult to distinguish the lower part of the Marshall from the under-lying Goldwater in the subsur- face, coarse grained sandstone and conglomerates of Goldwater-Lower Marshall age are common. "The upper part of the Marshall, the Napoleon sandstone, is commonly white to gray in color and is coarser grained than the lower Marshall. In some areas it is pink and red. The top or upper part is very shaly and dolomitic. "The Michigan.formation consists of dark gray shale, gypsum, dolomite, and limestone with some sandstone. In areal distribution it covers the central part Of the Southern Peninsula, about hO per- cent of the Michigan Basin. The thickness ranges from a few feet to about 500 feet with an average of about 350 feet. The lower part averages about 110 feet thick and consists of dolomite, shale, sandstone, and subordinate amount of gypsum. This unit, which includes all rocks from the top of the "Brown dolomite," is a per- sistent and easily recognized bed of wide distribution. "The upper part of the Michigan is characterized by an abundance Of gray to pink gypsum. In some places as much as hO percent of the rock sequence is gypsum. "Lying unconformably above the eroded Michigan and unconform- ably below the thick black shale of Pennsylvanian age is a section of sandstone, limestone and dolomite Merimecian in age--the youngest Mississippian rocks of the Michigan Basin. These rocks, which are from a few feet to about 300 feet thick, can be divided into four parts in the Central Basin area. The basal part is about 30 feet thick and consists of a tan to brown dolomite or limestone, sandy in parts, which is usually correlated with the Bayport or Point Au Ores limestone that crOps out in the Saginaw Bay area. Above the basal dolomite are gray sandstone beds composed of medium, angular to sub- angular quartz grains. The sandstone and underlying dolomite or limestone is recorded in some well logs as Parma-Bayport although the Parma sandstone as defined at the outcrop is of Pottsville Age." CLASSIFICATION OF BRACHIOPODA In 1929, Schuchert and LeVene's (Twenhofel and Shrock, 1935, p. 282) published the following classification Of brachiOpods: Phylum BrachiOpoda Class Articulata Order 1. Paleotremata Superfamily l. Paterinacea Superfamily 2. Rustellacea Superfamily 3. Kutorginacea Order 2. Atremata Superfamily l. Obolecea Superfamily 2. Lingulacea Superfamily 3. Trimerellacea Order 3. Neotremata Superfamily l. Siphonetretacea Superfamily 2. Acrotretacea Superfamily 3. Discinacea Superfamily h. Craniacea Class Articulata Order h. Protremata Superfamily l. Orthacea Superfamily 2. Clitambonacea Superfamily 3. Dalmanellacea Superfamily h. SyntrOphiacea Superfamily S. Pentameracea Superfamily 6. StrOphomenacea Order 5. Teletremata Superfamily l. Rhynchonellacea Superfamily 2. Atrypacea Superfamily 3. Spiriferacea Superfamily h. RostrOSpiracea Superfamily S. Terebratulacea COOper (Shimer and Shrock, 19th, page 283) modified Schuchert and Le Vene's classification as follows: Class Inarticulata Order Atremata Superfamily Obolecea Superfamily Trimerellacea Order Neotremata Superfamily Paterinacea Superfamily Siphonotretacea Superfamily-Acrotretacea Superfamily Discinacea Superfamily Craniacea Class Articulate Order Paleotremata Impunctate Articulata Superfamily Orthacea (including Clitambonacea) Superfamily Syntrophiacea Superfamily Pentameracea Superfamily Triplesiacea Superfamily Rhynchonellacea Superfamily Spiriferacea (including.Atrypacea, Spiriferacea, and RostrOSpiracea) lO Pseudopunctate Articulate Superfamily StrOphomenacea Superfamily Productacea Punctate Articulate Superfamily Dalmanellacea Superfamily Terebratulacea Superfamily Punctospiracea Since this study is concerned only with the genera that are included in the Class Articulate, COOPer's discussion of the reasons for modifying that class are quoted below: "The Articulate are generally subdivided into Paleotremata, Protremate, and Telotremata. The first contains only two genera of primitive calcareous shells without fully develOped articulation and delthyria. The Protremate are described as having delthyria in both valves, which are often more or less closed by a pseudo- deltidium and chilidium. The brachial supports are rudimentary. The Telotremata, on the other hand, are described as having the delthyrium more or less closed by deltidial plates and a lopho- phore supported by crura, loops, or spines. As a matter of fact, these simple statements are misleading; in actuality the delthyria are variously modified. Discovery of deltidial plates in the Protremate and what appears to be a pseudodeltidium in Telotremata leads to confusion in the two orders. Add to these complications the presence of a loop in the impunctate, protremate Enantiosphen, and the confusion becomes still greater. It seems best, therefore, in order to make separations easier, not to use the ordinal characters of the Protremate and Telotremata as defined, but to arrange the super- families falling in these orders according to the three types of shell structure into which the Articulate are divisible. The arrangement above ”(COOper's modified classification)" is not at present proposed as a genetic classification; it would require the demonstration that lOOps and spires were developed independently in the punctate and impunctate brachiopods. This is a possibility, but present knowledge does not permit such a demonstration. Never- theless, it seems clear that the punctate and pseudo-punctate shells were derived from the impunctate Orthacea." Most of the descriptions of genera are quoted from Shimer and Shrock, l9hh, in which.COOper's modified classification appears. For the purpose of consistency, COOper's classification will be used in this paper. ll CRITERIA USED FOR DESCRIBING AND NAMING-BRACHIOPODA A. Size and shape of shell. B. Dimensions of the shell. C. Degree of convexity of valve. D. Location and degree of various lepes of the valve. E. Character of umbo and beak. F. Character and location of mesial sulcus and, or mesial fold. G. Internal characteristics. H. Surface ornamentation. It was disclosed that many of the Species described do not comply completely with the descriptions of forms by several paleontologists. The so-called "open nomenclature" was introduced to indicate isomorphism with a known species without deciding the question of identity. In describing the fossils the symbol "cf." is used to indicate similarity and "eff." for relationship with known Species. The symbol "?" is used for doubtful identification. For the purpose Of description shells whose width does not exceed 35 mm. and length is not less than 20 mm. the size shall be termed medium. When either the length or the width is in excess of 50 mm. the shell will be designated as being large. The tenm small is used in cases where neither the length nor the width is over 15 mm. 12 The writer has assigned the two forms thnchonella barquensis Winchell and Rhynchonelle subcircularis Winchell to the genus Camerotoechia. The two fOrms are homeomorphs differing only interiorly. The main dif- ference between the two genera is that Rhynchonella has dental plates while Camerotoechia is without dental plates. Since the genus Rhynchonella is now reserved for the Mesozoic this assignment was necessary. 13 SYSTEMATIC DESCRIPTION OF BRACHIOPODA Order Paleotremata Impuntate Articulate Superfamily Rhynchonellacea 'Subtriangular, rostate, generally costae with delthyrium usually closed by deltidal plates; foramen located just anterior to beak; lophOphore supported by cura' (Shimer and Shrock, 19bh, p. 307). Genus Camerotoechia (Hall and Clarke 1893) Genotype Atrypa congregate conrad IGenerally triangular, costate, uniplicete, with shallow ventral valve and strongly convex dorsal valve; ventral interior with well developed dental plate; dorsal interior with divided hinge plates; no cardinal process, and segments of hinge plate attached to median septum by supporting plates making a short, small cruralium often covered with growth of inner hinge plates." (Shimer and Shrock, 19th, p. 311). Camerotoechia camerifera Odinchell). Shell, small, subtriangular, cardinal margins at right angles slightly wider than long. The dimensions of a nearly perfectly preserved interior mold of a disarticulated specimen: length, 11.5 mm.; width, 11.5 mm.; thickness undeterminable. Ventral valve, convex along plane of symmetry; the curvature of the valve is nearly equal from the middle Of the anterior the surface curving more abruptly towards the poeterior; middle portion broadly flat, the 1h surface curving abruptly laterally; mesial sulcus obsolete in posterior portion; in the anterior portion the mesial sulcus is shallow, diverging, and at the anterior margin occupies one-third of the shell; beak incurved. Surface covered.by 20 to 21 sharp, simple costae that become finer as the cardinal extremities are approached; from three to four costae occupy the mesial sulcus. Dorsal valve, somewhat flattened mesial portion curvature to the posterior and anterior margins extremely abrupt, curving less abruptly to the anterior; median septum 3.5 mm. in length; mesial fold originating near the middle and projecting more or less over the anterior margin. Surface covered by costae similar to that of the ventral valve. Horizon: - Lower'Marshall formation. Locality: -- Barn locality, Huron County (Map NO. 2). Remarks: - The above described specimen agrees with the description and illustrations of“Winchell (1862, p. hOY) in every respect. Camerotoechia huronensis Var. Precipua (Winchell) (plate 1, figure 1). Shell a little below average--above small sixe, subovate in outline, wider than long. The dimensions of an almost perfect interior mold dorsal valve are: length, 15 mm.; width, 17 mm.; thickness approximately seven mm. Dorsal valve convex, mesial portion of the valve broadly flattened, curving abruptly to the posterior and anterior margins; transversely the surface curves abruptly to the cardinal extremities; a low, broad 15 and barely visible mesial fold.originates near the middle and projects slightly over the anterior margin; beak slightly incurved. Surface marked by about 22 low rounded costae of which 5 occupy the fold. Horizon: —- Goldwater formation. Locality: -- Lighthouse Point, Huron.Gounty. Remarks: -- The specimen was compared with the pictures of the syntype (plate 7, figure 2) and Winchell's description and appear to agree in every respect. Camerotoechia cf. hubberdi (Winchell) (plate 1, figure 2). Shell small, broadly subtriengular, length and width nearly equal. The dimensions of an imperfectly preserved interior mold of a dorsal valve are: length about 10 mm.; width, 10 mm. Dorsal valve convex, mesial portion somewhat flat, leping gently towards the front; approaching the anterior margins, the surface drOps vertically to the plane of commisure; the curvature is more gentle to the posterior. Mesial septum extends approximately one-third of the distance from the beak to the anterior; mesial fold wanting. Surface covered by approximately 20 rounded costae which become fainter laterally. Horizon: -- Lower Marshall formation. Locality: -- The bed of“Willow'Creek near Huron City, Huron County. Remarks: -- This Specimen greatly resembles G, hubbardi Winchell (Lane, 1900, p. 275), except for the abrupt geniculation at the anterior. It also differs from'Winchell's type in the more rounded cardinal extremities. 16 Camerotoechia selixensis Nov. sp. (plate 1, figure 3). Shell, small, subtriengular, cardinal margin at right angles or nearly so, length and width nearly equal, greatest width near midpoint. The dimensions of a nearly perfectly preserved interior mold are: length, 10 mm.; width, 10 mm.; thickness, 8 mm. Ventral valve convex, from midpoint the surface curves somewhat abruptly to the anterior, more gently to the posterior; mesial portion more or less flat, curving abruptly to the posteriO-lateral and anterio- 1ateral margins; a broad shallow mesial sulcus originates near the middle and occupies one third of the anterior margin; beak incurved; laterally the dental plates are parallel, vertically they diverge at an angle of approximately LOO. Seven fine rounded costae occupy the mesial sulcus. Horizon: -- Lower Marshall formation. Locality: -- Bed of Willow Creek near Huron City, Huron County. Remarks: -- This specimen is characterized by sides that SlOpe obliquely, from the mesial portion to the cardinal extremities and its fine rounded costae. An investigation of the literature reveals that this form had not been described previously as a member Of the Lower Marshall fauna. Camerotoechia Species "A" (plate 1, figure h). Shell small, subtriengular, wider than long, lines tangent to cardinal margins at right angles. The dimensions of a nearly perfectly preserved interior cast of a disarticulated specimen are: length, 11 mm.; width, 12 mm.; thickness, 7 mm. 1? Ventral valve convex, point of greatest convexity near middle, surface curving sharply to posterior, gentle to the anterior, and very moderate to the anterio-lateral lepes; a shallow, triangular, mesial sulcus originates near the middle and extends to the anterior margin; beak incurved; dental plates diverge at an angle of 30°. Surface covered by approximately 20 to 26 fine sharp costae of which from five to six occupy the mesial sulcus. Dorsal valve less convex, mesial portion somewhat flat, curving abruptly to the posterior, less abruptly to the anterio-laterel margins and gentle to the anterior margin; mesial fold obsolete on posterior half of shell, on the anterior half extending from the middle to slightly beyond the anterior margin. Surface markings similar to Opposite valve. Horizon: -- Lower*Marshall formation. Locality: -— Bed of Willow Creek near Huron City, Huron.Gounty. Remarks: -- Division of this species was attempted on the basis of the number of costae and it was noted that although the number Of costae varied in a number of individuals the morphology of the shell was similar in all cases. Therefore it is believed that they are conspecific and have been grouped into one Species. In the opinion of the writer this Species is believed to be a mutation of Camerotoechia camerifera Winchell. Camerotoechia (Rhynchonella) barquensis (Winchell) (plate 1, figure 5). Shell small, transversely oval, wider than long. The dimensions of an imperfectly preserved interior mold dorsal valve are: length, 9 mm.: width, 12 mm.; thickness approximately 5 mm. 18 Dorsal valve convex, mesial portion broadly flat, curving abruptly to the posterior and anterior; transversely the curvature is also abrupt to the posteriO-lateral margins; a sharply defined mesial fold originates beyond to the middle and projects slightly over the anterior margin. Surface covered by 16 sharp simple costae of which four occur in the mesial fold. Horizon: -- Lower Marshall formation. Locality: -- Barn locality south of the Grindstone quarries, Huron County. Remarks: ~~ In general, the characteristics of this specimen are in agree— ment with the description of Winchell (1862, p. hO8). The above specimen, however, has more costae than the one described by Winchell. The writer believes that this difference is not of sufficient significance to warrant a new species, and that this specimen is conspecific with R. barquensis. Camerotoechia (Rhynchonelle) subcircularis CHinchell) Shell small, broadly subtriengular, The dimensions are concealed and cannot be determined accurately. Dorsal valve convex, curving gently to the anterior margins, some- what Stronger to the posterior; beak abruptly depressed; median septum long and extending about two—fifths the distance to the anterior margin. Surface marked by fine, simple, rounded costae. Horizon: -- Lower Marshall formation. Locality: -- Barn Locality south of the Grindstone quarries, Huron County. Remarks: -- The specimen can be distinguished easily by its long mesial septum, which extends beyond the mid-length. l9 Superfamily Spiriferacea "Articulate having lOphophore supported by a spiral brachid- ium and dethyrium modified by pseudodeltidium or deltidal plates" (Shimer and Shrock, 19kb, p. 317). Genus Spirifer (Sowerby, 181h) Genotype Anomites striatus Martin "Medium sized to large, transverse, generally with hinge forming widest part; completely costate; dental plates stout; brachidium.with many coils laterally directed; jugum incomplete; cardinal process roughened area under beak" (Shimer and Shrock, 19th, p. 325). Spirifer biplicoides Weller (plate 1, figure 6) Shell of medium size, broader than long, greatest width along hinge- line. The dimensions Of a partially destroyed inner mold of a dorsal valve are: length, 16.5 mm.; width along hinge—line, 32 mm. Dorsal valve convex, greatest convexity posterior to the middle also curvature of surface more abrupt, to the anterior the slope more gentle; transversely from midpoint, curvature abrupt becoming more gentle, at the cardinal extremity the surface is somewhat flattened; mesial fold defined by two sharp furrows that are broader than those between the other costae, slightly depressed posteriorly, and somewhat elevated anteriorly; mesial fold simple at the beak divided by a median furrow; towards the front it is again subdivided; another subdivision occurs and approximately at the midpoint, the furrows created by the subdivision of costae are extremely weak. 20 Horizon: -- Lower Marshall formation. Locality: -- Point aux Barques, Huron County. Remarks: -- Comparison of this Mississippian form with S. biplicioes Weller (plate 5, figure 1) from the Waverly of Ohio Shows the third bifurcation of costae on the outer edge of the mesial fold revealed on the Michigan Species also occurs on the Ohio species but is much fainter, otherwise they are in complete agreement. §pirifer aff. centronatus Winchell (plate 1, figure 7) Shell medium sized, subtriengular, much wider than long; cardinal extremities mucronate points. The dimensions Of a partially preserved inner mold of a ventral valve are: length, 10 mm.; width along hinge- line, 28 mm.; convexity, 3.5 mm. Ventral valve strongly convex along plane of symmetry becoming more gently convex as the cardinal extremities are approached; at the cardinal extremities the surface is almost flat; umbo prominent, surface of the valve compressed laterally; beak small incurved; curvature more abrupt from the middle to the cardinal margins. Surface marked by 36 fine, simple rounded costae which originate along the cardinal margin and become successively smaller towards the cardinal extremities; mesial sulcus shallow and narrow, bounded by a pair Of broad costae which are stronger than any others on the valve; the center of the mesial sulcus is marked by a median costa which is visible only on the anterior lepe below the midpoint, but it is believed to pass from the beak to the anterior margin; on either side Of this median costa are two costae 21 that originate by bifurcation on the inner margin of the broad costae. Horizon: -- Lower Marshall formation. ' Locality: -- Point aux Barques, Huron County. Remarks: -- S. species "A" is slightly smaller and more compressed laterally than the homeotype specimen of Spirifer centronatus (plate 8, figures land. 2) . Spirifer Species "A" (plate 1, figure 8). Shell below medium size, subtriengular, greatest width along hinge- line, cardinal extremities angular. The dimensions of a poorly preserved interior mold Of a dorsal valve: length, 1h mm.; width, 30 mm. Dorsal valve, gently convex, greatest convexity from midpoint to posterior and cardinal margins; mesial fold divided by weak furrow ex- tending from the beak to anterior margin; entire fold defined by pair of strong furrows deeper than those between the costae; the mesial fold barely elevated above the general surface. Surface marked by approxi- mately 2h rounded, simple costae that become weaker as the cardinal margin is approached. Horizon: -— Lower Marshall formation. Locality: -- Point aux Barques, Huron County. Remarks: -- Because of the poor preservation, no exact identification of this specimen could be made. Genus Athyzis (McCoy, 18hh) 22 Genotype Terebratula concentria Buch "Subequally biconvex; transversely elliptical, subcircular to elongate-ovate; exterior smooth or lamellosa; ventral valve sulcate, dorsal valve with low fold; foramen circular; ventral interior with short stout dental plates; dorsal interior with apically perforate hinge plate; median edge low; jugum complex" (Shimer and Shrock, p. 333). Athyris lamellosa Levielé ? Shell medium size, transversely subelliptical, wider than long, rounded cardinal extremities. The dimension of a poorly preserved interior cast of a ventral valve are: length, 22.5 mm.; width, 31.5 mm. Ventral valve convex, from the middle the valve curves abruptly to the posterior, gently to the anterior and anterio-laterel margins; mesial sulcus originating near beak, pOSterior narrow end sharply defined; as the anterior is approached the bottom becomes more rounded and faintly defined. Surface marked by two somewhat strong, concentric lamelliform extensions, which along the plane of symmetry measure five mm. apart. Horizon: -- Lower Marshall formation. Locality: -~ Point aux Barques, Huron County. Remarks: -- The Marshall Specimens were compared with a specimen of Athyris lamellosa Levielé (plate 5, figure 2) loaned to the writer by Dr. G..A. GOOper of the United States National Museum. In general the Michigan specimens agree, but due to imperfect preservation specific identity is doubtful. Psuedopunctate Articulate Superfamily StrOphomenacea 23 ”Pedicle threadlike, emerging from a tiny apical foramen or strophied if shells lie free on see bottom or are attached by more or less of ventral surface; pseudodeltidium and chilid- ium.usually well develOped; lOphophore supported by short brachiophores" (Shimer and Shrock, l9hh, p. 335). Genus Schellwienella (Thomas, 1912) _ Genotype Schellwienella inflate (White and Winfield) "Shell resupinate, costellate, ventral valve irregular, dorsal valve convex; deltidium closing the delthyrium, dental lamellae short and widely divergent, medium septum absent (Weller, l9lh, p. 59). Schellwienella sp. Shell above medium size, subelliptical in outline, greatest width near middle, cardinal extremities somewhat rounded, hinge-line short. The dimensions of a deformed inner mold of a ventral valve are: length, 3h mm.; width, hh mm.; width of hinge-line, 3h mm. Central valve nearly flat; mesial sinus Obsolete; cardinal angle about 100°; median septum not observable. Surface covered by fine sub- angular costae of which three occupy the space of one millimeter, in- creasing by bifurcation and implantation. Horizon: -— Goldwater formation. Locality: -- Rock Falls, Huron.Gounty. Remarks: -- The specimen at hand is an interior mold of a ventral valve with the posterior portion imperfectly preserved but no portion of the exposed.mold Shows any trace of the former position of a mesial septum. TOgether with the presence of a resupinate character the form suggests Schellwienella rather than Schuchertella or Orthotetes. 2h Schellwienella sp. (plate 2, figure 1). Shell above medium size, transversely subelliptical. The measure- ment of a fragmental, deformed, interior mold of a ventral valve is: length, +h3 mm. Ventral valve nearly flat, slightly concave in central position; somewhat elevated in umbonal region. Surface marked by fine, almost rounded costae which increase in number by bifurcation and implantation towards the posterior; two to three occupy the Space of a millimeter. Horizon: -- Goldwater formation. Locality: -- Near Diamond Greek north Of Port HOpe, Huron.Gounty. Remarks: -- Same as preceding Schellwienella. Superfamily Productacea uAbberrant shells usually with shallow body cavity and one or both valves provided with hinge or body spines serving as anchor struts, or supports" (Shimer and Shrock, l9hh, p. 3&5). Genus Ghonetes (Fischer, 1837) Genotype Ghonetes variolata Orbigny "Generally semi-elliptical to semicircular in outline, large of small, concavo-convex in profile hinge straight; posterior margin of ventral valve provided with oblique, hollow Spines; ventral interior with large flabellate muscle field and more or less well defined median septum; dorsal interior with erect quadrilobate cardinal process, low median septum" (Shimer and Shrock, 19bh, p. 3&5). Ghonetes Species "A" (plate 2, figures 2 and 3). 25 Shell small, subelliptical to subtriengular concavo-convex varies from wider than long, to sub-equal, cardinal extremities angular. The dimensions of an interior cast of a disarticulated specimen are: length, 6 mm.; width, 8 mm. Ventral valve convex, greatest convexity near middle, strongest curvature from middle to posterior, more gentle to the anterior; trans- versely, surface slopes abruptly from midpoint and approaching pardinal extremities becoming flattened; mesial septum varies from two to three mm. in length. Dorsal valve moderately concave, greatest concavity near midpoint, becoming flattened towards cardinal extremities; cardinal process small. Interior surface marked by two strong, wide furrows originating near cardinal process and gently diverging towards anterior margin. Surface of both valves marked by fine costae that increase by bi- furcation upon the posterior SIOpe; nearing the anterior margin in some individuals the costae bifurcate again into smaller costae. From four to five costae occupy the Space of one millimeter. Horizon: -- Goldwater formation. Locality: -- Rock Falls, Huron County. Remarks: -- The major difference between this specimen and Ghonetes scitulus Hall (plate 5, figures 3-h) loaned to the writer by Dr. G. A._ GOOper, is the size and the mode of occurrence. The Michigan specimens are in general small, and occur in a fine grained calcareous sandstone. On the other hand 9, scitulus Hall occurs in a black argillaceous lime- stone and are someWhat larger than the Michigan Specimens. In the writer's 26 Opinion Ghonetes Species "A“ could either be a series of small individu- als or mutations. Genus Dictyoclostus (Muir-Wood , 1930) Genotype Anomites semireticulatus Martin uGenerally large with reticulate umbonal region and costae trail having few erect spines; dorsal valve geniculate without spines and without diaphram" (Shimer and Shrock, l9hh, p. 3A9). Dictyoclostus cf. arcuatus Hall (plate 2, figure h). Shell below medium size, greatest width near mid-length. Ventral valve geniculate, with abrupt anterior lepe. Umbonal region partly concealed rather broad, with the lateral and anterior lepes curving abruptly. Median sulcus absent. Surface of the valve covered by fine round costae. Bifurcation noted near geniculate border of the valve. Costae continue anteriorly without division or coalescence; the average distance between the centers of two adjacent costae in the anterior lepe measures one and one-half millimeters. Spine bases can be observed on the left lateral slope. Horizon: :- Lower Marshall formation. Locality: -- The bed of the'Willow Greek near Huron City, Huron.Gounty. Remarks: -- Due to the large concealed areas of the single Specimen the characters of the umbonal and bordering area cannot be observed. The Specimen is tentatively assigned to the genus Dictyoclostus rather than 27 to LinOprOductus. The letter genus commonly shows flexuous and cooelesc- ing costae which are not present on this specimen. Dictyoclostus cf. fernglenensis (Weller) Ventral valve gibbous, the mesial portion broadly flat or nearly so, becoming more abruptly rounded laterally; mesial sulcus absent. Surface covered by rounded, costae which increase by bifurcation on the posterior slope. The costae are crossed by concentric, wrinkle-like markings that become stronger posteriorly. Horizon: -- Lower Marshall formation. Locality: -- Burnt Cabin Point, Huron County. Remarks: -- Examination of 2. cf. fernglenensis Weller revealed that the transverse section is more convex than Productus fernglenensis Weller, (191R, p. 106). Also, 2. cf. fernglenensis is somewhat smaller than Weller's type. Comparing the specimen with other productidae however it is apparent, that due to the broadly flat mesial position of D, fernglenensis, the Michigan form more closely resembles 2. fernglenensis, Identification is uncertain due to the lack of preservation of the anterior margin of the Specimen. Genus Echinoconchus CNeller l9lh) Genotype anomites punctatus Martin ”Shell productoid in form and with internal characteristics as in the genus Productus. The external surface of the valves marked by more or less sharply differentiated concentric bands 28 which commonly grow broader in passing from the beak to the outer margins, each band bearing numerous, crowded fine, Oppressed imbricating spines, either subequal or unequal in size, which are produced from elongate node-like bases." (Shimer and Shrock, l9hh, p. 138). Echinoconchus aff. biseriatus Hall (plate 3, figure 1). Shell small, length and width approximately equal, the greatest width near anterior. The approximate dimensions of a imperfectly preserved inner mold specimen of a ventral valve are: length from umbonal region to anterior margin, 18 mm.; greatest width, 18.5 mm. Ventral valve strongly convex, surface curves abruptly to the cardinal margin, more gently to the anteriO-lateral margins; mesial sulcus obsolete. Surface marked by concentric bands that become wider as the anterior is approached and are slightly elevated along their anterior margin; upon these bands are situated a row of faintly visible elongate nodes, which are the bases of Oppressed spines. Near the posterior margin Of the con- centric bands the nodes are barely visible, becoming high and well defined as the posterior margin Of the band is approached; scattered in front and between these nodes are numerous finer, but similar nodes which are the bases of finer oppressed spines. Horizon: -- Bayport formation. Locality: -- Bayport Quarry, Huron County. Remarks: - This small individual compares closely with E. biseriatus Hall loaned through the courtesy Of the United States National Museum. It also resembles E. morbillianus UNinchell) for which there is an emended description by Weller (l9lh, p. 1h2). 29 In a later publication Sutton (1938, p. 555) listed E. morbillianus as Pustula morbilliana (Winchell). The two distinct rows of spines possessed by this specimen leaves no doubt that it is an Echinoggpchus. Echinoconchu§ aff. genevievensis Weller (plate 3, figures 2.and 3). Shell above medium size, somewhat broader than long, hinge-line much shorter than greatest width. The dimensions of a nearly perfectly pre- served specimen are: length from beak to anterior margin, h3 mm.; length from hinge-line to front margin, 33 mm.; greatest width, hh mm.; width of hinge-line, 28 mm. Ventral valve strongly convex; umbonal region prominent, projecting beyond hinge-line; surface curves abruptly to cardinal margin and gently to anterior margin; mesial sulcus originating near beak becoming rounded in the bottom and broad laterally; beak incurved. Surface covered by concentric bands whose width along plane of symmetry varies from two to four millimeters. Posteriorly each band is depressed; band is posteriorly marked by elongated spine bases; small Spine bases are crowded in front and between the elongated spine bases. Dorsal valve gently concave, except cardinal margins which are some- what flettened; near the middle a low rounded mesial fold originates, becoming stronger towards the front. Surface markings similar to Opposite valve. Horizon: -- Bayport formation. 3O Locality: -- Kaven's Quarry, Arenac County. Remarks: -- This well preserved complete specimen is somewhat larger than the type specimen recorded by Weller (l9lh, p. lhO). Echinoconchus aff. gppevievensis Weller (plate 3, figure II). Shell slightly above medium size, broader than long, hinge-line shorter than meximum width, greatest width anterior to midlength. The dimensions of a partially broken almost perfectly preserved specimen are: length from umbonal region to anterior margin, 36 mm.; length from hinge- line to front margin, 27.5 mm.; greatest width, 38 mm. Ventral valve strongly convex, greatest depth between mid-length and posterior, umbonal region prominent and narrow, protuberant beyond hinge- line; the surface curves gently to the anteriO-lateral margins and abruptly to the cardinal margin; mesial sulcus originating in the moderate- ly wide and deep umbonal region. Depth of sulcus not well defined lateral- ly, and rounded at the bottom. The beak is strongly incurved and pointed. Surface marked by regular concentric bands from two to four millimeters in width, upon which are two rows Of elongated bases Of spines, the finer being situated anteriorly. Horizon: -- Bayport formation.. Locality: -- Keven's Quarry, Arenac County. Remarks: -- This species resembles E. genevievensis Weller, in surface ornamentation, but it is proportionally larger. In addition the mesial sulcus originates anterior to the umbonal region. 31 Echinoconchus aff. ggnevievensis Weller (plate 3, figure A). The dimensions of an imperfectly preserved dorsal valve are: length from hinge-line to anterior margin, 27 mm.; greatest width, b2 mm.; width of hinge-line, 3h mm.; length of median septum, 10 mm. Dorsal valve gently concave, except near the cardinal extremities which are flattened; near the middle a low round mesial fold begins and becomes somewhat stronger towards the anterior margin. The surface is marked by concentric bands similar to those Of the ventral valve. Horizon: -- Bayport formation. Locality: -- Point aux Gres, Arenac County. Remarks: -- See remarks on preceding specimen. Genus Linoproductus (Chao, 1927) Genotype Productus core Orbigny "Small or large, generally costellate with small visceral cavity and long trail; umbonal SlOpes and ears Often concentric- ally wrinkled; deep visceral chamber" (Shimer and Shrock, l9hh, p. 351). Linoproductus ovatus Hall (plate 3, figure 6). Shell variable in size, length greater than width; hinge-line shorter than greatest width. The dimensions of an imperfectly preserved ventral valve are: length from hinge-line to front margin 32.5 mm.; length from umbonal region to anterior margin, 36 mm.; greatest width, 29.5 mm.; length of hinge-line, 2b.5 mm. 32 Ventral valve gibbous, greatest convexity posterior ro the middle. The umbonal region very prominent and strongly protuberant beyond the hinge-line; transversely the posterior curvature more abrupt. From the mesial portion of the valve the curvature is very gentle, almost flattened; as the lateral lepes are approached the curvature becomes abrupt; mesial sulcus absent, beak pointed and strongly incurved. Shell thin and commonly exfoliated, the surface marked by narrow, rounded, somewhat flexuous costae. The costae increase by intercalation; in.places coalesce; upon the posterior lepe of the valve the implanted costae increase in size and become less frequent toward the anterior margin where the costae are more flexuous and approximately two costae occupy the Space of one millimeter. On the right lateral lepe and near the cardinal extremity small wrinkle- like folds extend up the lateral lepes, becoming less distinct, and finally disappearing as the middle of the valve is approached. A single, somewhat elongated spine base is observable on the left lateral 510pe near the anterior margin. It may be the base Of‘a broken spine which commonly characterize this genus. Horizon: -- Bayport formation. Locality: -- Bellevue Quarry, Eaton County. Remarks: -- In general, the lepe from the mesial portion of the valve to both cardinal extremities is different from Weller's (l9lh, pp. 132- 13h) description and the National Museum specimen (plate 6, figures 6-7). The Michigan specimen is somewhat broader across this area. The absence of small auriculations near the cardinal extremities are interpreted as the result of imperfect preservation. The differences in size between 33 the Michigan specimens and those figured and described by Weller, and borrowed from the U. S. National Museum (plate 6, figures 6 and 7) are regarded as individual variations, or the result of ecologic conditions. Linoproductus ovatus Hall (plate h, figure 1). Horizon: -— Bayport formation. Locality: -- Bellevue Quarry, Eaton County. Remarks: -- This, a single specimen from the same locality as Lingproductus gygipgd does not possess the broad curvature which extends from the middle portion of the cardinal extremity. It agrees in shape and size with Weller's (l9lII, p. 132) description. LinOproductus eff. tenuiccstus Hall (plate h, figure 2). Shell thin, medium size, somewhat longer than wide, hinge-line shorter than greatest width. The dimensions of an incomplete specimen are: length from hinge-line to front margin, 2h mm.; length from umbonal region to front margin, 30 mm.; greatest width, 25 mm.; length of hinge- line, 26 mm. Ventral valve gibbous, greatest convexity between beak and middle, umbonal region protuberant beyond hinge line and broad; transversely the mid-surface is slightly undulate for approximately one-half the total length of the valve; the lateral slopes curve abruptly to the lateral margins becoming slightly inflected towards the cardinal margin; a gentle curvature marks the anterior SIOpe; the slope flares slightly towards the left antero-lateral margin; the valve somewhat compressed towards the 3h cardinal extremities to form prominent auriculations. Surface marked by fine, rounded, irregular costae, that radiate from the umbonal region; costae about one-half millimeter apart. Bifurcation of the costae may be noted is present on posterior and anterior lepes; intercalation and anastomosing lirae in close proximity; regular, concentric, elongate, wrinkle-like mounds mark the posterior slope of the valve, becoming stronger towards the cardinal margin, approximately midway between the beak and the middle; the position of the wrinkle-like markings suggests bifurcation; fine concentric growth lines cover the surface. Spine bases may be observed scattered along the lateral lepes midway between the beak and the anterior margin. A few scattered Spine bases occur on the middle part of the pedicle valve; in all cases, the Spine bases are centered on the costae, which Continue up to and past the spine's base. Horizon: -- Bayport formation. Locality: -- Kaven's Quarry, Arenac County. Remarks: -— The view that this specimen is the same as L. ovatus could be held were it not for the fact that L. tenuicostus is a semireticulate form while L. ovatus is not. The umbonal region Of L. aff. tenuicostus is much narrower than that of L. tenuicostus (plate 6, figure 8 and 9). There also seems to be a difference in the size of the costae. On the whole, L. eff. tenuicostus has larger costae. Linoproductus eff. tenuicostus Weller (plate h, figure 3). Horizon: -— Bayport formation. Locality: -- Unknown. 35. Remarks: -— As was noted in the discussion of the previous form, the costae of this individual is somewhat larger than the holotype specimen borrowed from the United States National Museum (plate 6, figures Band 9). The question is then raised, "what is the difference between Linoproductus and Dictyoclostus?" On this subject A. H. Sutton is quoted as follows: "Members of this genus "(Linoproductus)" possess a hinge- line that is characteristically shorter, relatively, than that of the semireticulate forms. The rugae are normally less dis- tinct on Linoproductus than Dictyoclostus. Forms with costae of intermediate size, if they have a long hinge-line and well develOped rugae, have been assigned to Dictypclostus and the ones with the relatively short hinge-line, to Linoproductus." Due to the fact that this specimen possesses a short hinge-line (12 mm.), plus cooalescing costae, and a pronounced geniculate shell it was assigned to LinOproductus. Examining the Spine bases that appear on the body of the valve it is interesting to note that they occur not only like those that have been previously described, but on this specimen one spine base seems to span three costae on the posterior side of the spine base. However, on the anterior side, there is only one costa that continues on to the anterior margin. Also, a spine base on this specimen forces the costa to enlarge. The adjacent costae either disappear or swerve out around the enlarged part of the costa. Punctate Articulate Superfamily Delmanella "Subcircular to elliptical plano- to biconvex Shells having brachiophores and generally a small lobate cardinal process! (Shimer and Shrock, l9hh, p. 351). 36 Genus Rhipidomella (Oehlert, 1890) Genotype Terebratula micheline L'Eveillé I'Generelly circular in earlier forms becoming subtriengular in later ones; compressed biconvex, finely costellate; hinge very narrow; ventral interior with large flabellate muscular field; dorsal valve with thick brachial processes and large bilobed cardinal process' (Shimer and Shrock, 19kb, p. 355). Rhipidomella Sp. Shell small, subovate, length and width approximately equal, greatest width anterior to middle, hinge-line less than one half the greatest width. The dimensions of the interior mold of a nearly perfect ventral valve are: length, 12.5 mm.; greatest width, 1h mm.; length of hinge-line, 6 mm. Ventral valve most convex posterior to middle; umbo rather prominent; surface slopes abruptly to cardinal margins, curving gently to anterior margin; the mesial portion flattened from the middle to the anterior, umbo slightly protuberant beyond hinge-line. Surface covered by fine, unifOrm, rounded radiating costae of which usually three occupy the space of one millimeter. Horizon: e- Lower Marshall formation. Locality: -- Point aux Barques, Huron County. Remarks: -- This specimen appears to possess scattered spine bases. However, Weller (l9hh, p. 1h?) discloses that the costae of Rhipidomella are hollow and often Open on to the surface giving the shell a punctate character. The Specimen being an interior mold, it is highly probable that the "spine bases" are merely the internal mold of these openings. 37 This Rhipdomella closely resembles E, burlingtonensis in shape and outline. However, it is approximately one-half the size of E. burlington- ensis. Genus Syringothyris (Winchell , 1863) Genotype §yringothyris type "Usually large with ventral valve subpyramidal; fold and sulcus noncostae; entire surface covered with minute pustules; ventral interior with long divergent dental plates; dethyrium partly covered with flat apical plate" (Shimer and Shrock, l9hh, p. 363). I Syringpthyris pharovicina Winchell (plate b, figure h). Shell above medium size, subpyramidal in form, cardinal margins curving from beak to cardinal extremities, greatest width along hinge-line. The dimensions of a partly destroyed interior mold ventral valve are: length, 2h mm.; width along hinge-line, b6 mm. Ventral valve, greatest curvature from middle to cardinal margins, curving more gently to anterior and anterio-lateral margins; transversely, the surface slopes abruptly from the midpoint, approaching the cardinal extremities the surface is somewhat flattened; mesial fold defined by a deep wide furrows, a weaker furrow divides the mesial fold from the anterior to near the umbonal region. Surface marked by simple rounded costae. Horizon: -- Goldwater formation. 38 Locality: -- Lighthouse Point, Huron County. Remarks: -- The distinguishing pustule-like surface of the mesial fold cannot be determined because of the eroded condition of the specimen, but the form agrees with the description and illustrations of S. pharovicina Winchell (plate 8, figures 1 and 2) . Syringothyris Species "A" Shell above medium size, wider than long, greatest width along hinge- line. The dimensions of an interior mold of a broken distorted dorsal valve are width, £8 mm.; length, 25 mm. Dorsal valve subpyramidal, surface convex from umbo to lateral and anterior margins, curving more abruptly to cardinal margins; mesial fold faint outline can be seen, surface characters cannot be determined; each lateral lepe marked by 16 rounded simple costae that grow fainter approach- ing the cardinal extremity. Horizon: -- Lower Marshall formation. Locality: -— Near Diamond Creek north of Port HOpe, Huron County. Remarks: -- The general characteristics suggest that this specimen is a Syringothyris. Syringothyris cf. textus (plate h, figure 5). Shell large, broader than long, the greatest width along the hinge- line, angular cardinal extremities. The dimensions of a disarticulated imperfectly preserved specimen are: minimum length of the ventral valve 39 from beak to front margin, h2 mm.; length of dorsal valve, 33 mm.; width along hinge-line, 90 mm.; thickness, h2 mm.; width of sulcus in front, 20 mm.; width of delthyrium at hinge-line, 18 mm. Ventral valve gently convex slope from beak to anterio-lateral margin; lepe from beak to anterior margin gently convex but more abrupt than the SIOpe to the anterio-lateral margin. Mesial sulcus non-costae, but like the surface of both valves it is covered with minute pustules; mesial sulcus is narrow and well-defined in umbonal region anteriorly the mesial sulcus is broad and well defined. Each lateral lepe is marked by simple, depressed rounded costae which originate along the cardinal margin. The number of costae cannot be counted on the dorsal valve; the slope is gentle with a convex curvature from the beak to the cardinal extremities; lepe increases slightly approaching the cardinal extremities. Internally, the dental plates are moderate in length and thick; they measure 22 mm. in length and are one-half millimeter in width. The syrinx is indicated by a rounded, interior mold and bisects the angle between the two sides of the delthyrium. Neither the adductor or its scars are preserved. Dorsal valve strongly convex, the surface is convex from the cardinal margin to the anterior margin along the plane of symmetry, and also from the cardinal margin to the anterio-lateral margins. The curvature is also abrupt towards the cardinal margin; towards the cardinal extremities the surface is compressed. The non-costate mesial fold is smooth except for pustules and is depressed towards the beak; the mesial septum divides the mesial fold into two separate parts. The depressed, rounded simple costae ho which number 21 on the lateral lepe originate along the cardinal margin. Horizon: -- Goldwater formation. Locality: -- The Quarry of the Wolverine Cement Company south of the city of Goldwater, Branch County. Remarks: -- The specimen of Syringothyris cf. textus was compared with a slightly deformed specimen of Syringothyris textus deposited in the Uni- versity of Michigan biological collection and it was determined that S. cf. textus possesses a more rounded mesial fold and a lesser number of costae. A unique characteristic which aided in the identification is the sinuousity of the costae on the ventral valve, indicative of a thin shell in contrast to Brachyspirifer which has a thick shell. Superfamily Terebratulacea "EndOpunctate brachiOpods having lOphophore supported by a brachidium in the form of a more or less complicated loop" (Shimer and Shrock, l9hh, p. 363). Genus Centronella (Billings, 1859) "Small rhomboidal in outline, ventral valve longitudinally subcarinate; dorsal valve concave, surface smooth; ventral interior with thick dental plates and large teeth; dorsal valve with ponderous divided hinge plate; 100p short, the decending lamellae meeting a short longitudinal plate" (Shimer and Shrock, l9hh, p. 363). Romingerina julia Winchell Shell minutely small, almost circular, varies from wider than long to longer than wide. The dimensions of an interior mold of a nearly hl complete specimen are: length, h mm.; width, 3.5 mm. Both valves have a lens-like convexity. Ventral valve convex throughout; beak incurved and circularly forami- nated; in some specimens a gentle front ridge extends the length of the valve. Entire surface smooth and having punctate character. Dorsal valve similar except for the absence of a beak. Horizon: -- Lower Marshall formation. Locality: -- Barn Locality, Huron County. Remarks: -- The Specimen was not sectioned. Its association with g, Camerifera, and its easily identifiable external characteristics leave little doubt about its identification. The internal characteristics described by Winchell (lb62, p. hos) are quoted as follows: "A delicate ribbon-like 100p, originates from the stout blunt cura of each side of the pocket valve, having its flat sides at first vertical; the two branches of the loop proceed at first in lines parallel or a little convergent, and gradually diverge, widening as they proceed, and assuming an inclined position, until, approaching the front of the valve by a regular curvature, the lower edge has become anterior, giving the band an angle of 30° with the plane of the shell; approaching the median line the band rapidly widen and the front margin is drawn forward in a long acumivation, while the inner margin is regularly concave, except that near the median line it turns abruptly for- ward so as to meet that line at an acute angle. The loop thus forms an urceolate figure on its inner margin, and on the outer margin a somewhat oval one truncates behind and attenuately acuminate before. In the median line where the two branches meet, both are suddenly deflected downwards, forming a double vertical plate, not quite reaching the ventral valve, the upper edge of which, when viewed from the side, is flatly roof-shaped, while the lower edge describes two convexities, the greater anterior, leav- ing a notch between them. The surface of the loop and median plate are covered with minute obliquely conical pustules, in some places seeming to become Spinulous. The casts exhibit on the ventral side a delicate impressed line extending from the beak to the middle and on the right and left of this fainter one; on the h2 dorsal side a median impression with two fainter ones on the right, and two on the left--the median termination rostrally upon a small pyramidal process (filling the beak of this valve) separated by a short slit (made by the socket ridge) from a smaller isolated process on each side. " This Species was first assigned to Centronella. ‘Winchell, however, discovered a modification of the 100p structure which differed from Centronella. Hall and Clarke (189h, pp. 273-h) erected a new genus Romingerina based upon different loop structure. h3 DISCUSSION OF FAUNAL ASSEMBLAGES Goldwater Formation In the abandoned quarry of the Wolverine Cement Company south of the city of Goldwater, in Branch County, a thin bed of clay ironstone formation is exposed in the Goldwater shale. This layer contains many unoriented and disarticulated inner molds 0f Syringothyris cf. textus Hall. The brachiOpod S. textus Hall occurs in the Keokuk limestone in Illinois Cfleller, lQIh, p. 399). Meek (1875, p. 285) notes the presence of S, textus Hall in the shale of the Waverly group in Ohio. S, tgxtgs Hall is preserved in a sandstone facies near the t0p of the New Provi- dence formation, the lowermost of the Borden group in Indiana. The biozone of this species, as correlated with the type section, comprises a major portion of the Osage group. The value of this species as a time marker is therefore seriously limited because of the great stratigraphic thickness in which such specimens occur. However, it may be used as an approximate time-equivalent with those beds containing Similar fossils in adjoining states. Since the occurrence of §. textus Hall is restricted to the Goldwater locality its time-equivalent significance is doubtful. Camarotoechia huronensis var. precipua CNinchell) and Syringothyris pharovicina Odinchell) occur in outcrOps near Lighthouse Point in.Michigan. Both of these forms are found in gray, shaly, sandstone. S. pharovicina is also present in a conglomerate in this vicinity. uh A sample collected from the rock exposures near Rock Falls, Huron County, contains inner molds of Ghonetes sp. "A" and a ventral valve of Schellwienella. These specimens are preserved in sandstone whose litho- logy iS similar to that of the sandstone at Lighthouse Point. The Specimens of Ghonetes sp. "A", as pointed out in the systematic description of this form (See pp. 2L-25), may be mutations of Ghonetes scitulus Hall, which is known to occur in Devonian as well as in Mississ- ippian strata (GOOper, 1900, p. 172). Therefore, if the identification is correct, 9. scitulus Hall cannot be considered as having exact time- equivalent significance. The single occurrence of this specimen in the outcr0p near Rock Falls eliminates its stratigraphic use within the Michigan Basin. Schellwienella sp. which occurs in the same locality, may be conspecific with a form in Indiana. A specimen of Schellwienella sp. occurs in the Goldwater outcrop at Diamond Creek north of Port H0pe within these two localities Schellwienella may be considered as time- equivalent. The individuals Camerotoechia huronensis var. precipua Uflinchell) and Syringothyris pharovicina Odinchell) appear to be restricted to the Lighthouse Point locality and have not been reported outside of the State. A search of the literature failed to disclose the presence of conspecific forms in adjacent states. Lower Marshall Formation The lower Marshall brachiOpods Camerotoechia cf. hubbardi, (Winchell) Camarotoechia saliexensis Nov. sp., Camarotoechia species "A. and LS Dictyoclostus cf. arcuatus Hall are preserved in a host rock of rusty brown, fine-grained and weathered, sandstone. This faunule was collected from an outcrop in the bed of the'Willow Creek, near Huron City, Huron County (Map No. 2). A second faunule includes Camerotoechia camerifera Odinchell) E, barquensis Odinchell), g. subcircularis (Winchell), and Romingerina julia Winchell. This, too occurs in the lower Marshall from the "Barn Locality" (Map No. 2) approximately one half mile east of Grindstone City. The R. julia zone is either directly above the Grindstone beds or separated by a thin concealed layer of shale. This well-marked zone, according to Lane (1900, p. 269) occurs approximately 220 feet below the top of the lower Marshall. From Grindstone City southeast to the Willow Creek locality, the absence of any outcr0p of sandstone prevents the determination of the relative stratigraphic position of the exposures in the lower reaches of Willow Creek with those at the Grindstone City area. The brachiopods found at the Willow Creek and in the Grindstone City area are not conspecific with any species found in adjacent states. How- ever, other evidence casts doubt upon the possibility that these forms are restricted to the Michigan Basin. According to W. A. Kelly (personal communication, 1952), P. B. Stockdale was impressed by the Similarity of the lower Marshall fauna in the Point aux Barques area with some of the sandstone fauna of the Borden group of Indiana. The possibility exists, therefore, that these forms migrated in their planktonic stage by way of the Chatham sag, or some other route, whereby the Mississippian sea could have gained admittance to the Michigan Basin. It is difficult to determine h6 their time-equivalent significance due to the slow rate of migration. However, it is believed that in a general sense they are equivalent to those of the Borden group. Because these two localities are the only known outcrOps in.Michigan where these lower Marshall species occur, their time-equivalent value is unknown within these restrictions of the Michigan Basin. The small producted, Dictyoclotus cf. arcuatus Hall, occurs in the massive Logan sandstone of Ohio (White, l9h8, p. h3) and in the sandstone of the New Providence formation of Indiana. This species also is present in the Lower Marshall sandstone in the valley of the Willow Creek. Dictyoclostus cf. arcuatus Hall probably can be used as a time-equivalent because of its relative short biozone and occurrence in the same rock type. The Single Specimen of Dictyoclotus cf. fernglenensis Weller was collected from the sandstone of Burnt Cabin Point (Map No. 2). The occurrence of this individual in the lower Marshall is probably due to the following of a favorable environment into the Michigan Basin. This form may be time-equivalent with 2. fernglenensis Weller of the Fern Glen formation of the Mississippi Valley. Near Point aux Barques in Huron County, large erractics of gray, sandy, Marshall limestone were found. Their occurrence on shore is probably due to ice rafting. Because of their dislocation, the exact stratigraphic position cannot be determined. In general the angular appearance and occurrence in slabs several square feet in area, suggest a source close by and in the bed of the Lake Huron. Specimens from h? these erratics are listed below: Bryozoa: Fenestrellina BrachiOpoda: Athyris lamellosa Levielé ? Dictyoclostus sp. Linoproductus sp. Rhipidomella sp. Spirifer biplicoides'Weller Spirifer aff. centronatusldinchell Pelecypoda: a small smooth form GastrOpoda: a inner mold of a minute form Athyris lamellosa Levielé according to Weller (l9lh, p. h6S) occurs in the Burlington and Keokuk limestones of the Mississippi Valley. Logan (1922, p. hS) cites the presence of g, lamellosa Levielé in the sandstone and limestone beds of the New Providence formation. The same species also occurs in the shale of the Waverly group of Ohio (Meek, 1875, p. 288). The Species Spirifer biplicoides Weller (plate 1, figure 6) was com- pared directly with a form preserved in sandstone of the Waverly group from Ohio (plate 5, figure 1). The Michigan and Ohio specimens agree in every reSpect. Spirifer aff. centronatus Winchell when compared with the homeotype, from the Cuyah0ga shale of Ohio reveals a minor difference (See page 20). It appears likely that these species have migrated stratigraphically into the Michigan basin by following a favorable environment and therefore are considered to have little time—equivalent value for long range h8 correlation. Athyris lamellosa Levielé, Spirifer biplicoides Weller and Spirifer centronatus‘Winchell are restricted to one slab from the shores of Lake Huron near Point aux Barques (Map No. 2) therefore their time- equivalent value within.Michigan is doubtful. Bayport Formation The two brachiOpods Linoproductus ovatus Hall and Linoproductus aff. tenuicostus Hall are preserved in the white, granular limestone in the quarry near Bellevue, Eaton County. Similar brachi0pods, together with the species Echinoconchus aff. biseriatus Hall and Echinoconchus aff. genevievensis Weller, occur in several localities previously listed (See pp. 30-38) in Arenac County. Weller (l9lh) discloses the presence of E. genevievensis and E. biseriatus Hall in the St. Genevieve and St. Louis limestones. LinoRro- ductus ovatus Hall has a wide geologic range occurring in the Burlington, Keokuk, Salem and St. Genevieve limestones reSpectively. The only re- ported occurrence of L. tenuicostus Hall is in the St. Louis limestone. W. A. Kelly (personal communication, 1952) states that the coral Lithostrotionella is found in the Bayport of Michigan as well as in the St. Louis limestone. Lithologically both formations are similar in that they are cherty. The St. Louis is characterized by a large number of geodes while in the Bayport, a single geode has been found. The St. Louis attains a maximum thickness of 325 feet in the area represented by the St. Louis quadrangle h9 (Weller, 191b, p. 21). The limestone member of the Bayport formation seldom exceeds 25 feet in thickness. Due to the thinness of the Bayport and the similarity of faunas, the outcrops of the Bayport may be used as a time-rock unit in Michigan. The Bayport fauna, together with the occurrence of the coral Lithostrotionella, suggests that the Bayport is the time equivalent of the St. Louis and possibly part of the St. Genevieve. The presence of g. aff. biseriatus Hall, E, aff. genevievensis Weller, L. ovatus Hall, L, aff. tenuicostus Hall and the coral Litho- strotionella in the Michigan is due probably to the rapid migration of these Species in a favorable environment of warm, clear waters. 50 CONCLUSIONS The most significant conclusions resulting from this study are: 1. The time-stratigraphic value of the Mississippian BrachiOpods of the Goldwater and Lower Marshall formations within the Michigan Basin can not be determined because no two outcrops have similar faunas that can be correlated. 2. The Bayport formation may be used as a time-rock unit within the Michigan Basin. Inter-regionally the Bayport formation is the time-equivalent of the St. Louis Limestone and possibly a part of the St. Genevieve limestone. 3. The Species occurring in the Goldwater and Lower Marshall form- ations are restricted to the Lower Mississippian. 51 BIBLIOGRAPHY Baltrusaitis, E. J. and Clark, C. K. (19h8) "A summary of the Strati- graphy of the Southern Peninsula of Michigan." Mich. Geol. Society, Mimeographed paper, pp. 10-13. Hall, J. and Clarke, J. M. (18%,) 53 Introduction 33 33119. Study 9; thg Gepera gf_Palaeozoic BrachiOpida, Geol. Sur. of New York, New York, pp. 189-191 and 271—272. Holden, F. T. (19b2) "Lower and Middle Mississippian Stratigraphy of Ohio," Jour. Geol. Vol. 50, p. 67. Hyde, J. E. (1915) "Stratigraphy of the Waverly Formations of Central and Southern Ohio," Jour. Geol., Vol. 23. pp. 655—682. Hyde, J. E. (1927) "The Mississippian Systems," in Wilbur Stout: Geolo. 2f Vinton County, Ohio Geol. Sur., hth Ser., Bull. 31, pp. h3-EE. Krumbein,'W. C. and 81038, L. L. (1951), Stratigraphy and Sedimentation, W. H. Freeman and Company, San Francisco. pp. 22D-251. Lane, A. C. (1900) Geological Report 22 Huron County, Michigan, Mich. Geol. Sur., Vol. VII Robert Smith Printing Go., Lansing, Mich., pp 0 1-297 0 Logan et a1., (1922) Handbook gf_Indiana Geology, Ind. Dept. of Consv., Publ. No. 21. pp. 380-579. Meek, L. B. (1875) "A Report on Some of the Invertebrate Fossils of the ‘Waverly Group and Goal Measures of Ohio," Geol. Sur. of Ohio, Vol. II, Nevins and Meyers, Columbus, Ohio, pp. 283-28h, 285-288. Moore, R. c. (1928) Early Mississippian Formations in Missouzi, Missouri Bureau of Geology and Mines, 2nd. Ser., Vol. 21, pp. 262-278. Newcombe, R. B. (1933), Oil and Gas Fields pf Michigan, Mich, Dept. of Consv., Geol. Sur. Div., Publ. 38, Geol. Ser. 32, p. 59. Prosser, C. S. (1912) The Devonian and Mississippian Formations of Northeastern Ohio, Geol. Sur. of Ohio, Lth Ser., Bulletin 15: pp. 530-519 . Shimer, H. W., and Shrock, R. R. (l9hb) Index Fossils 3£_North America, Johnldiley and Sons, Inc., New York, pp. 2E7-276. 52 Stockdale, P. B. (1931) "The Borden (Knobstone) rocks of Southern Indiana," Ind. Dept. Consv. Div. 0601., Publ. No. 98, pp. 210-215. Stockdale, P. B. (1939) "Lower Mississippian Rock of the East Central Interior," Geol. Soc. Am., Special paper #22, pp. hO-78, 166. Sutton, A. H. (1938) "Taxonomy of Mississippian Productidae," Jour. Paleo., Vol. 12, No. 6, pp. 537-569. Sutton, A. H. (l9h3) "Cardinal Process or Productidae," Jour. Paleo., Vol. 17, No. h, pp. 323-330. Stauffer, c. R., Hubbard, G. D. and Bownocker, J. A. (191h) GeolOoy 9g the Columbus Quadrangle, Geol. Sur. of Ohio, hth Ser., Bull. 1h, p. 50. Twenhofel, W. H. (1935) Invertebrate Paleontology, McGraw Hill Book Company, Inc., pp. 25'-300. von;Zitte1, K. A. (1913) Textbook gf Paleontology, Macmillan Go., Limited London, pp. 355-365. 'Weller, Stuart, (191A) Mississippian Brachiopoda of the Mississippi Valley Basin, Ill. Geol. Sur., Mono. I, pp. 1-29, 53:68; 103-135; l39-Ih3, 157-151, 175-185, BOY-hon, hon-b67. 'Winchell, Alexander (1862) "Descriptions of Fossils from the Marshall and Huron Groups of Michigan." Proc. Acad. Nat. Sci. Philadelphia, pp. hos-30. PLATES AND EXPLANATIONS The illustrations contain specimens from the following collections: plates one through four species described in this study, plates five and six are composed of forms loaned through the courtesy of the United States National'Museum, plates seven and eight contain type specimens borrowed from the Museum of Paleontology of the University of Michigan. All figures are twice their natural size. Figure Figure Figure Figure Figure Figure Figure Figure 1. 2. EXPLANATION OF PLATE 1 Camerotoechia huronensis var Precipua (Winchell) 1. Interior mold of a dorsal valve Goldwater formation, Lighthouse Point, Huron County Camerotoechia cf. hubbardi (Winchell) 2. Interior mold of a dorsal valve Lower Marshall formation, the bed 93 Willow Creek near Huron City, Huron County Camerotoechia salixensis Nov. Sp. 3. Inner mold of a ventral valve Lower Marshall formation, the 33.93. 9.: the Willow Creek near Huron City, Huron County Camarotoechia Species "A" 1;. Inner mold of a ventral valve , Lower Marshall formation, the bed 2! Willow Creek near Huron City, Huron County Camarotoechia (Rhynchonella) Barquensis (Winchell) 5. Dorsal valve Lower Marshall formation, Barn locality, Huron County Spirifer biplicoides Weller 6. Dorsal valve Lower Marshall formation, Point aux Barques, Huron County Spirifer aff. Centronatus Winchell 7 . Ventral valve Lower Marshall formation, Point aux Barques, Huron County Spirifer species "A" 8. Dorsal valve Lower Marshall formation, Point aux Barques, Huron County PLATE 1 Figure 1 Figure 2 Figure )4 Figure 5 ' Figure 6 Figure 7 EXPLANATION OF PLATE 2 Figure 1. Schellwienella 1. View of interior mold of ventral valve Lower Marshall formation, outcrop_along ttg Diamond Creek north.2£ Port Hope, Huron County Figure 2-3. Ghonetes species "A" 2. View of interior cast of a ventral valve 3. View of interior cast of a dorsal valve Goldwateg formation, Rock Falls, Huron County Figure h. Dictyoclostus cf. arcuatug Hall h. Interior mold of ventral valve Lower Marshall formation, the Egg 2£,Willow'Creek near Huron City, Huron County. PLATE 2 Figure 1 Figure 2 Figure 3 Figure )4 Figure Figure Figure Figure Figure 2-3. EXPLANATION OF PLATE 3 Echinoconchus aff. biseriatus Hall 1. View of interior mold of ventral valve. Bayport quarry, Bayport Michigan, Huron County. Echinoconchus aff. genevievensis Weller 2. Ventral valve. 3. Dorsal valve. Bayport formation, Kaven's Quarry, Arenac County. Echinoconchus aff. genevievensis Weller b. View showing concentric bands and spine bases of a ventral valve. Btyport formation, Kaven's Quarpy, Arenac County. Echinoconchus aff. genevievensis Weller 5. Dorsal valve showing mesial septum and cardinal process. Bayport formation, Point 335 Gres, Arenac County. Linoproductus ovatus Hall 6. Ventral valve. Bayport formation, Bellevue, Eaton County. PLATE 3 Figure 5 Figure 6 Figure Figure Figure Figure Figure 3. EXPLANATION OF PLATE h Lin0productus ovatus Hall 1. Ventral valve Egyport formation, Bellevue, Eeton.Cou ty. Linoproductus aff. tenuicostus Hall l. Ventral valve Bayport formation, Kaven's Quarry, Arenac County. Linoproductus aff. tenuicostus Hall 1. Ventral valve Bayport formation, Location unknown. Syringothyris ptarovicina Winchell l. Ventral valve Goldwater formation, Lighthouse Point, Huron.Gounty. syringothyris cf. textus Hall 1. Ventral valve Goldwater formation, south 2£_Coldwater, Branch County, PLATE Lt _ Figure 1 Figure 2 . Figure 3 Figure 11 Figure 1. Figure 2. Figure 3-h. Figure 5. EXPLANATION OF PLATE 5 Spirifer biplicoidtp Weller #366hh 1. Dorsal valve (interior mold) ‘Waverly £3222: Bagdad, Ohio Athyris lamellosa Leviele 2. Ventral valve . New Providence formation, Deerlick Knob, Clermont, Bullit County, Kentucky. Ghonetes scitulus Hall #10878 3-h. Interior molds of ventral valves. Ludlowville formation, ngggg Lake, New York. Productella gppuata Hall #911 5. Ventral valve Burlington limestone, Burlipgtop,Iowa, PLATE 5 Figure 3 Figure )4 Figure 5 Figure Figure Figure Figure Figure Figure 1-2. 6-7. 8’90 EXPLANATION OF PLATE 6 Echinoconchus alternatus Norwood and Pratten l. Ventral valve 2. Dorsal valve Keokuk formation, North 9.32 Warsaw Illinois. Echinoconchus biseriatus Hall #39137 3. Ventral valve Warsaw limestone, Colesbury Kentucky. Echinoconchus genevievensis Weller h. Ventral valve St. Genevieve limestone, Huntsville Alabama. Echinoconchus vittatus Hall 5. Ventral valve Keokuk limestone, Nauvoo Illinois Linoproductus ovatus Hall 6. Ventral valve 7. Dorsal valve . §t. Louis limestone, §t, Louis Missouri. Linoproductus tenuicostus Hall 8. Ventral valve 9. Dorsal valve St. Louis Limestone, Alton Illinois. PLATE 6 Figure Figure Figure Figure Figure Figure Figure 10 EXPLANATION OF PLATE 7 Gamarotoechia camerifera (Winchell) syntype #h390 1. Ventral valve Lower Marshall formation, Point aux Barques and Grindstone Quarries, Huron Count . Gamarotoecha huronensis var. Precipua Odinchell) hypotype {2217 l. Ventral valve Qpper Goldwater formation, Point aux Barques Lighthouse, Huron.Gounty. Gamarotoechia hubbardi Odinchell) syntype #26803 1. Dorsal valve Lower Marshall formation, Marshall, Eaton County. Gamarotoechia micropluera OdinChell) holotype #b382 l. Dorsal valve Lower Marshall formation, Battle Creek. Gamarotoechia subcircularis Udinchell) holotype #26802 1. Dorsal valve Lower’Marshall formation, Point aux Barques and Grindstone Quarries, Huron County. Gamarotoechia whitei UNinchell) holotype #h382 l. Dorsal valve Lower Marshall formation, Marshall, Eaton County. Eumetria polypluera Winchell syntype #2226 l. Dorsal valve Upper Goldwater formation, Point aux Barques Lighthouse, Huron.Gounty. PLATE 7 Figure 5 Figure 6 Figure Figure Figure Figure h-S . EXPLANATION OF PLATE 8 Spirifer centronatus Winchell holotype #h565 1. Ventral valve 2. Mold of Figure 1 gEyahoga shale, ngahoga Falls Ohio. Spirifer huronensis Winchell hypotype, #2213 3. Ventral valve Upper Goldwater formation, Point aux Barques Lighthouse, Huron County. Syringothyris pharovicina Winchell hypotype #2215 h. Ventral valve 5. Dorsal valve Lower Marshall formation, Lighthouse point, Huron County. Romingerina julia.Winche11 syntypes #h390 6. Ventral valve 7. Dorsal valve Lower Marshall formation, Huron County. PLATE 8 Figure l at.) it ‘ III). 3' Fig. No.2. CO LUMNAR SECTION OF MISSISSIPPIAN ROCKS IN MICHIGAN (GENERALIZED) SYSTEM SERIES GROUP FORMATION OR MEMBER LITHOLOGY DESCRIPTION THICK- NESS MEC MERA' BAYPORT ', LIMESTONE, Brn.—Gry.,8 SS. 40-IOO' MERAMEC-OSAGE MICHIGAN "-———————. —-———__ ///////// Hfi 0— -——— __ _ I ——-—..————-——. : SANDSTONE-Gry. DOLOMITE LIMESTONE SHALE - Gry. 0-500' FEROUS p K ERHOO CARBON S D MARSHALL j SANDSTONE, Red a White, :Some SHALE 8 SILTSTONE . 11111 ISO-320' COLDWATER ——.—-fi-—.———‘ I - ._ F. — —.~.—— - —— _ —— Z a SILTSTONE SHALE Gry., Some Red SHALE, Some SANDSTONE SOO-IOOO SUNBURY -—-—- SHALE, Blk. Io-eo' BEREA ...... . . g . o O SANDSTONE, White 8 Gry., a SHALY SANDSTONE 0-2IO' BEDFORD —..—..———_.—4 p———_—.-—-— ——-———.—-—.__ -_——.——-————1 SHALE, Gry. lO—BOO' I I "\D I I I DEVONIAN 0. DEV. a L. MISS. ANTRIM —'———.-——_-.———d SHALE, Blk. ICC-400' From: Monnet,V.B. II948), "Mississippian MorshoIl Vol. 32, No. 4. p. 630. Formation of Michigan”, BULL. AMER. ASSOC. PETROL. GEOL, A.L.Oden COLUM NAR SECTION 0 F MISSISSIPPI AN ROCKS IN OHIO (GENERALIZED) SYSTEM FORMATION LITHOLOGY DESCRIPTION MAXVILLE VIN TON -._ '° .-" “I"; -‘ SANDSTONEfineJroined,ptShon. ALLENSVILLE a, 3 '. ‘ ' SANDSTONE.Goorse grained. BYER ,7 r- SANDSTONE,Fine grained. SHALE, Gry FEROUS _ ‘ .:_.-. ~31“. SANDSTONE,Fine grained Io Con- BLACK HAND ~ ' ‘ glomerotic. CUYAHOGA (3 IX RTB (DIV I SUNBURY , BEREA .- ANDS ONE Grit Beoroao - SHALE, Gry. KINDERHOOK .---?---- >. LIJ CD From: Newcombe,R.B,(l933), OIL AND GAS FIELDS- OF MICHIGAN, Michigan Department of Conservation, Geol. Sur.Div., Publ.38 Geol. ser.32,p.50. SHALE, em. Hyde,J.E. (I927),THE MISSISSIPPIAN SYSTEM,inWiIbur Stoui-j GEOLOGY OF VINTON COUNTY, Ohio Geol. Suvey, 4th sen, BuII.3I, p.43'64. A.L. Oden (GENERALIZED) m 0. FORMATION THICK- SYSTEM 3.: 8 0R LITHOLOGY DESCRIPTION MESS uJ n: MEMBER m (D 1 I I I I I I I I I I I I I I I I IN I I z 1 r1 Hr tr ' r U) STE. GENEVIEVE r [4.131 LIMESTONE, Ll. colored, Cross- 0-245' LIMESTONE lj II 1%.] bedded,in port Arenoceous. I) <1 I I I FI I I I 8 I : T :111; I [T O - 2 I I F I <1 I I I I I a: I I n I I a: “J I I [III I_1 I T 2 ST.LOUIS I I ItL LIMESTONE, Ltcolored, finely I I L_I . , Lu 0.. LIMESTONE FI I I 1 I TJ 1 IT crystalline to dense, in port 0- 325 I I I, I ,J I I lithographic. I I L U- —- III I I I I LI II I I ' I 1* —- U) [TI II ; Iil I I I II I I , WARSAW III] III i] LIMESTONE, inoporl Lithographic, O’lGO z (D FORMATION I T I L In part DolomItIc. J I I I I -_I__'_I__J:_a_ o .— {‘5‘ KEOKUK ‘ F I— r‘ “ I" LIMESTONE, Mdssive 5:) LIMESTONE 77—???g: SHALE, Gry. 0-75' I L I m . O I I I ' T‘ 11 ' . BURLINGTON , I II I I I Ij LIMESTONE, LI.c0I0red,Mossive, O‘ISO LIMESTONE T I 1 r 1 coarsely crysIoIIlne. a: I I I I I I I I I _ FERN GLEN LMS. Ir—g—Izl-EI LIMESTONE, Shaly. 0-40“ 4 “' CHOUTEAU r‘ r' r' .2 L LIMESTONE, Drab gry. Dense. 0-55' x LIMESTONE 11,1,I,VrL u 2— 8 HANNIBAL _l~.,::_:—__: SHALE, Sandy. . g; FORMATION :—‘:~:—T:“_ SANDSTONE, Fine grained. 040° 3 GLEN PARK LM‘S. .—I—_‘.—.-I-i_;.—‘—_—T—_—_Q— LIMESTONE a SHALE 0-4' :25" LOUISANA _,I II I I :Eii LIMESTONE, Gry. Lithographic. 0-67' LIMESTONE ,‘ 1' ,I ,T, T Descriplion 3 Thickness From: Weller,S.(I9I4),THE MISSISSIPPIAN BRACHIOPODA OF THE MISSISSIPPIAN VALLEY BASIN, III. Geol. Surv., Mon. I,pp. I-23. Stratigraphic Succession From: Moore, R.C.(I928), EARLY MISSISSIPPIAN FORMATIONS IN MISSOURI, Mo.Bur. Geol. Mines , 2nd. sen, V0I.2I, pp. l3. Fig.No.5 A.L.Oden I‘IICHIGQN STQTE UNIV. LIBRQRIES IILIIILIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII 293010137150