I “v I“! m I I I ’II II I I I I I III | I II I I I I II I I I b I O1 ’I'HE FERRON POINT AND GENSHAW FORMATIONS IN CHEBOYGAN AND WESTERN PRESQUE ISLE COUNTIES, MICHIGAN Thesis for the Degree of M. S. MICHIGAN STATE COLLEGE George Wendell Smith I 942 THE FERRCN POlNT AND GENSHAW FORMATlONS IN CHEBOYGAN AND WESTERN PRESQUE lSLE COUNTTES, MICHldAN by George Wendell Smith A THESIS Submltted to the Graduate School of Micnlgan State College of Agriculture and Appllea Selenee 1n partial fulfilment of the requirements for the degree of MASTER OF SCIENCE Department of Geology and Geography 1942 THESIS Introduction - - - — - - - - _ _ _ Nature of the problem - - - — - - - Location and boundaries of the Acknowledgments - - - - - - a Field procedure - - — - — - - General tepography of the area _ - Abandoned channels along Milligan Distribution and classification of and Ferron Point formations Classification - - - - - - - Correlations - - - - - - - - Description of Sections Locality 1 — _ - _ - _ - _ _ -I>' \N m I I I I I I I I I ” 5___.__-._~_ u 5__._______“ .. 7__.__-.___~ 5 3--..---..-_ u 9____-______ 142804 area the Creek — Genshaw I HS" #WIUIUH O’\ ‘78 11 Description of sections (Continued) Page Locality 14 - - - - - - — - - - - - - 38 " 15 - - - - - - - - - - - - - 39 ” 16 - - - - - - - — - ~ - - - 59 Systematic description of fossils - - - - 41 Faunal zones and correlation of sections - 70 Environment of deposition - - - - - - - - 74 Structural geology - - - — - --------- - - 76 Summary and conclusions - - - - - - - - - 84 BibliOg*aphy - - — - — - - - - - - — - - — 86 ILLUSTRATIONS Following Elélfi Page I. Geologic map of Afton-Cnaway area, Richigan - 76 II. Fig. A. View of old tributary of Nilligan Creek - - - - - - - - ----- 8 Fig. B. View down old channel along Eil- ligan Creek ---------- 8 III. Structural contour map, Afton-Cnaway area - - 76 1. Index map showing location of area studied - - 2 2. Sketch map of a portion of Milligan Creek - - 7 3. Correlation chart of named geologic units in the Traverse Group of rocks in Michigan - - - — - - ---------- l4 4. Geologic section across Sec. 34, T. 35 N., R. 1 s. - - - - - - - - - - - - - - - — — 27 iii Following Fimure Page 5. Correlation chart of outcrOp sections - - - - 70 o. Chart showing stratigraphic range of fossils used in faunal zoning - - - - — - 71 INTRCDUCTICN NATURE CF THE PROBLEM This thesis is the result of an examination of the faunal zones of the Ferron Point and Genshaw formations in Cheboygan and western Presque Isle counties, Michigan. These formations are in the lower part of the Traverse Group of rocks of middle Devonian age. The primary objec- tive of this study was the preparation of a geoloaic map and a structural contour map, based on the stratigraphic position of outcrOps determined through faunal studies. The relation of the topography to the areas of outcrOp is discussed. Fossils collected at several exposures of the Ferron Point and Genshaw are listed. An attempt is made to determine those faunal zones which can be used as stra- tigraphic guides, since lithology is of little value for this purpose in the Genshaw formation. The distinctive lithologies of the Ferron Point formation and of the Killians member of the Genshaw aid in establishing the stratigraphic position of several outcrops. The brachio- poda which are of stratigraphic value in zoning are de-~ scribed. New species are not named inasmuch as it is un- derstood that Dr. G. A. COOper of the U. S. National Mu- seum has in preparation a monograph on the Brachiopoda of the Traverse Group of Michigan. Fossils found to be of no use in stratigraphic zoning are not described but are included in the faunal lists. LOCATION AND BOUNDARIES OF THE AREA The region in which this study was made is in the north central part of the lower peninsula of Michi- gan.. (See index map, Fig. 1). This report describes the Genshaw and Ferron Point formations in west-central Presque Isle and Cheboygan counties.. The area, contain- ing about 40 square miles, includes all known outcrOps of the Genshaw and Ferron Point formations in Cheboygan county. The area in which outcrOps are found is bounded on the north and south by the Pleistocene glacial drift in Townships 34_and 35 North.. The irregular western edge of the area Of outcrop lies about two and one-half miles west of Afton.. (See Pl..I). This village is on the sou- thern line of Sec..36, T. 35 N., R. 2 W.. The eastern boundary runs north and south two miles east of the Cheboygan- Presque Isle county line.. ACKNOWLEDGMENTS The writer is deeply indebted to Dr..w. A. Kelly of the Department of Geology at Michigan State College for suggesting this area as a subject for study. Dr. Kelly gave freely of his time and knowledge in both the field and laboratory. To Mr..H..K..Martin and Lt. W..J..Anderson the writer expresses his thanks for assistance in the field.. Mr..Martin's aid in preparing the base map is gratefully remembered.. Mr..J....Young, Jr., was most helpful with MICHIGAN SCALE or MILES ........................................ .............. snore-oOI-Inololooo' IIIIIIIIIII 0.I¢..!:u INDEX MAP SHOWING LOCATION OF AREA STUDIED Figure l. -3- paleontological problems.. He and Dr..L. L. Ray have read the manuscript and offered helpful suggestions. Dr..S. G» Bergquist furnished much information concerning the sur- face features of the area.. This assistance is thankfully acknOWledged.. The writer is indebted to J. B..Si for aid in the preparation of the manuscript.. The field work was made possible by financial assistance furnished by the GeoIOgical Survey Division of the Conservation Department of Michigan.. Laboratory work was performed with the aid of facilities furnished by the Department of GeolOgy and Geography, Michigan State 0011983 0 . FIELD PROCEDURE The writer first visited this area in May, 1941 and spent three days, under the guidance of Dr..w._A. Kelly, visiting outcrops of the Traverse Group of rocks.. At this time a traverse was run, several sections measured, and fossils collected from outcrOps of the Genshaw.. In June, 1941,.two and a half weeks were spent in measuring and describing stratigraphic sections, locating outcrOps, and collecting fossils.. Outcrops not accessible by auto were located by pace and compass traverses "tied" to section corners“ Preliminary faunal lists were prepared in the field. Most of the faunal zones were recognized in the field and were later confirmed by laboratory studies. -4- By utilizing these faunal zones and the distinc- tive lithologic characteristics of the Ferron Point forma- tion and the Killians member of the Genshaw, it was pos- sible to establish equivalence of outcrOp sections.. The thickest section of outcrop of the Genshaw formation is along Milligan Creek.. The faunal zones found there were later discovered in similar stratigraphic positions in other exposures.. To obtain vertical control, essential to both structural and stratigraphic interpretations of the rocks, elevations were carried to every exposure by level and stadia rod traverses. Traverses were "tied" to U. S. Coast and Geodetic Survey bench marks or to secondary elevation points established by F..G..Dewell in 1935 by precise lev-u elling.. The geologic map was prepared after the pace and compass traverses had been plotted and corrected and the stratigraphic position of each outcrOp determined. GENERAL TOPOGRAPHY OE THE AREA_ The tepOgraphy of this part of Cheboygan and Presque Isle counties is that typical of a region which has been subjected to continental glaciation. The sur- face is low and rolling, and the relative relief of the area does not exceed 275 feet.. The glacial debris is relatively shallow over most of the area, but it obscures the bed rock except -5- along the stream valleys where it has been removed.. Only two natural exposures, in Secs. 34 and 36, T- 35 N., R..l E., are not along stream valleys.. The deepest mantle of gla- cial material is in the approximate center of the area shown on the map. (Pl. I). From near the center of Sec. 12, T..34 N., R..l w., to the point where Michigan Highway 23 turns northwest a mile north of Legrand the bed rock is concealed by a northwest trending esker.. For at least a mile on each side of the esker the rocks are buried., No outcrOps of the Genshaw or Ferron Point were found between Legrand and the Michigan meridian because of the glacial overburden.. An unpublished map prepared by Dr. S. C..Bergquist of the Department of Ge010gy, Michigan State College, shows that sandy lake plain follows the valley of the Upper Black River.. (See Pl. 1).. The map further shows that glacial till and ground moraine cover the remainder of the region, with the exception of a small area of glacial lake clay which extends from a mile and a half southwest of Legrand to within a quarter of a mile of Silver Lake.. (See Pl..I)- The direction of movement of the ice across the area is shown by glacial striae on the rock pavement at Tower Dam which strike S. 270 E.. Other striae on the Newton Creek limestone a mile and a half north of Onaway strike 5.. 32° E.. Drumlins occur at two localities in the area.. -"A series of well-defined elongated ridges with distinct troughs between them is situated -5- on the till plain immediately east of Onaway. The drumlins in this area are composed of bouldery till containing a heterogeneous mixture of all types of material, much of it of local derivation.. The till plain which carries the drumlins stands at an ele- vation of 600 to 900 feet above sea level and was formed by the ice of the Huron lobe as it retreated basin-ward from the main axis of the Port Huron moraine....They trend 5., 40° E....P (Bergquist, 1942, p..454.) The lack of alignment between the strikes of the striae and the trends of the drumlins constitutes a problem far beyond the realm of this discussion. Another group of drumlins occurs northeast of the village of Tower.. These have been mapped (Bergquist, Unpublished Map) as occurring in sections 25, 26, 35, and 36, T..35 N., R..l E., and in Sec..1, T. 34 N., R..l E. ABANDONED CHANNaLS ALONG MILLIGAN CREEK The close relationship between the tOpOgraphy and the areas where rocks crop out is best illustrated along Eilligan Creek. Along the valley of the Milligan the gla- cial debris has been removed by stream erosion. Several abandoned channels were found along the creek valley. One of these abandoned channels, in Sec..32, T. 35 N., R. l E., developed in two stages.. It has left two rock terraces which expose about ten feet of Genshaw limestone. A con- tinuous, natural ten-foot exposure of strata in the area of study is unusual because of the glacial drift.. (See pages 5 and 6).. For this reason and the fact that the develOpment of the channel is probably related to the Nd: hump . . £2253: . 432.525; . a . . .. n... .- w .. . , dfigww ma 0.....M... can 2h one ow. a .3 as; .1.» 3 Beam «no. 8550 -x 5:. - ozmowu. m . .u .89 NW . 9.... a. 1.x .2 . . Ym .4} 0234 zo_5wm.mmomo . 3 4. WW “uh... 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BROKEN LINES INDICATE UNCERTAINTT OF CORRELATION COMPILED <3 "WI/“408...- SMITH I94?- FIGURE 3. -15- COOper; and COOper and Aarthin-—194l" on Figure 3 shows stratigraphic position.) is now considered to have its closest affinities with the Losansport, although this Indiana limestone was once thought to be Cnandaga in age. It necessarily follows that the Genshaw and Ferron Point formations are older than the LOgansport, because they are older than-the Four-Kile Dam limestone. DESCRIPTION 9E SECTIONS In the following stratigraphic descriptions the locality numbers are those used by the writer. A few of these are localities which have been described in print by other workers, (Pohl, E. R., 1930; Deiss, C..F., 1932; thair, A. H., 1937;'Warthin, A. 8., Jr., and COOper, GS A., 1941), all of whom used the same numbers.1 The locality numbers below 53 which they used were "...established by the joint field party of the Michigan and United States Geological Surveys in 1926, and are used by Cooper in the U. S..National Museum." (Warthin and Cooper, idem., pa 9)- The Museum of Paleontology at the University of Michigan also uses this system of numbering. The writer has not duplicated any of the numbers that the other workers used in the map-area of this thesis. Those numbers in parentheses below the writer's locality numbers in the following discussion are those used by pre- vious workers in the area. -16- The stratigraphic sections are described in de- scending order.~ They are composites of exposures usually within a few hundred feet of each other. The locality descriptions, however, tell the location of the outcrOps which were used in the preparation of the composite sections. Locality l Discontinuous outcrOps in ledges along Pigeon River from the Old Elmer Dam down the river for about 1,500 feet. Lo- cated in Sec. 12, T. .34 13., R. 2 genshaw formation: Thickness Bed No. LitholOgy Feet Inches 7 Limestone: tan, dense, partly magnesian.. l 6 6 Shale: calcareous, light gray. 1 Covered interval 4 5 Shale: gray, plastic. 1 4 Limestone: buff-gray to brown, dense.. 3 3 Limestone: shaly, light gray. 2 6 Covered interval 2 2 Limestone:- dense, black, poorly bedded. 3 l Limestone: dense, light gray, lower half contains shale layers. 5 Total Thickness 21 Fossils: Bed 6: Echinoderma: Crinostyli Bryozoa: Fenestella sp. BrachiOpods: Athvris sp. Atryoa sp. (large) Chonetes sp..aff. g..fra1ilis Stewart Delthyris? sp.. Mucrospirifer sp. I Platyrachella? sp.. Productella sp.. Pelecypods: Pterinea sp.. CephalOpoda: Gomphoceras sp.. Cephalopoda, indet. -17- Bed 6 (Continued): Trilobita: grgetus sp. Fish plate, indet. Beds 3 and 4: Coelenterata: Favosites sp.. Brachiopoda: Cyrtina alpenensis Hall and Clarke Mucrospirifer sp. I Pentamerella? sp. SchiZOphoria sp. Cephalopoda, indet._ Bed 1: Coelenterata: Favosites sp..(digitate type) Prismatgphyllum sp. Brachiopoda: gthyris sp.- Atryoa sp. Chonetes sp..aff. g. frasilis Stewart Pholidostrophia sp. Platyrachella? sp.. Stropheodonta sp. aff. S..demissa (Conrad) Pelecypoda: Eterinea sp. Trilobita: Proetus sp. Locality g Small exposure along southern branch of Little Pigeon River, where it crosses the western section line of Sec. 24, T..35 N., R.-2 w. Thickness Bed Ko. Lithology Feet Inches 1 Limestone: gray, slabby, dense.. l 8 Fossilsz. Favosites sp., Prismatophyllum sp., Atryoa sp., and SChlZOQhOPla sp. (64%%2%%%%¥ (65) TOp of the,sub-Killians Genshaw and also the Killians member in exposures chiefly in road cuts along the southern lines of Secs. l9 and 24, and along the western boundary of Sec. 30. The best section of the Killians was measured in the -18- old railroad cut in Sec..3©.. Exact location of outcrops: SE3, SE2, Sec. 24; N31, N32, Sec..25; SW2, SW;, Sec. 19: T..35 N., R..2 w; and NW3, Sec. 30, T..35 H., R..l w. Genshaw fo mation, Killians member: Thickness Bed. No. Lithology Feet Inches 5 Limestone: black, shaly, crinoidal.. 5 6 4 Limestone: black, dense, thin-bedded. 3 3 Limestone: black, dense.. Poorly exposed. l2 2 Limestone: black, shaly, gray-weather- ing.. Base of Killians member. 5 1 Limestone: gray, shaly, and tan, slabby. Poorly exposed.. 2 OV Total Thickness 27 Fossils: Bed 5 is composed of little else than crinostyli cemented together with black shaly limestone. Bed 3: Crinostyli, indet., Brachiopoda: Chonetes sp..aff. Q..fragilis Stewart Cyrtina sp. Mucrospirifer sp. I Platyrachella? sp. Schizoghoria sp. Trilobita: Proetus sp.. Fish plate,.indet.. Bed 2: Coelenterata: Favosites sp.. Crinostyli, indet.. BrachiOpodaz. Athyris sp. Mucrospirifer sp. I Pholidostr0phia sp. SchiZOphoria sp. Strgpheodonta sp. Localit 4 (03) Outcrop of the Killians in Sec..6, T..34 N., R. l 3., where STATE Highway No..33 crosses Milligan Creek.. The section is poorly exposed, and fossils were not collected. -19- Locality 4 (Continued) Genshaw formation, Killians member: Thickness Bed No. Lithology Feet Inches 1 Limestone: black, shaly, slabby. 5 (Esti- Mucrospirifer sp..I abundant. mated) Locality 5 Milligan Creek exposures of the Ferron Point and Genshaw formations.- A traverse was run and elevations carried up- stream from the bridge of the Detroit and Mackinac rail- road across Milligan Creek, where the top of the Bockport Quarry formation is exposed. The traverse ended where Milligan Creek crosses the western line of Sec. 31, T. 35 N., R. l E. Beds 14 to 19 were measured in a high bluff in the north-central part of Sec. 31, where the Milligan makes a turn to the northwest. (Due north of the section number ”31” on P1. I). Beds 10 and 13 are found between the above locality and the point where the creek crosses the eastern line of Sec. 30, T. 35 N., R. l E. Bed 10 is exposed at the base of the ridge about 100 feet north of the point where Milligan Creek crosses the line between Secs. 29 and 30, T. 35 N., R. l E. The other beds occur in ledge out- crOps along the creek down the valley from this last point. Genshaw formation:‘ Thickness Bed No.. Lithology Feet Inches 19 Limestone: gray, thin-and irregularly bedded. 7 18 Limestone: gray, massive, fine to me- dium texture. Fragmentary fossils. 3 4 l7 Shale: calcareous, light gray, soft. I 16 Limestone: gray, massive. Lower 6 inches is coquina. l 6 15 Shale: calcareous, gray, crumbly. l 4 l4 Limestone: gray, poorly bedded. A 1-inch layer of shale at base.. 2 6 l3 Limestone: alternating light and dark gray, regularly bedded.. Silicified fossils.. 3 l2 Limestone: dark gray to black, shaly. 2 6 ll Limestone: light to dark gray, shaly layers. Poorly exposed. 9 10 Limestone: gray to black. Medium and well bedded. 3 6 9 Limestone: dark to light gray, shaly.. lo 6 Covered interval. 4 -20.. Genshaw formation (Continued): Thickness Bed No. Lithology Feet Inches 8 Limestone: dark gray, shaly, thin and poorly bedded. 2 6 7 Limestone: gray, crystalline, poorly bedded. 2 6 6 Limestone: dark to light gray, shaly. 5 6 5 Limestone: blue-gray to black, argil- laceous. 6 4 Limestone: dark gray, argillaceous. 4 Covered interval. 6 3 Limestone: dark bluish-gray, shaly. 3 2 Limestone: gray, irregularly bedded. 3 Ferron Point formation: 1 Limestone: greenish gray, soft, very shaly. 3 Covered interval. (Estimated). 1 Total Thickness 84 8 Top of Rockport Quarry formation. Fossils: Bed 17: Coelenterata: Favosites sp. Brachiopoda: Athyris sp. Atrypa sp. (large) Mucrospirifer sp. I Stropheodonta sp. Bed 15: Coelenterata: Favosites sp.; Horn Coral, indet.. Prismatophyllum sp. StromatOpora? sp..(small mamelons; colony cylindri- cal; rounded ends.) §.? sp. (large, widely spaced mamelons) Crinostyli, indet. Bryozoa, indet. Brachiopoda: Atryoa sp. (large) Mucrospirifer sp. I StrOpheodonta sp. aff. g..demissa (Conrad) S. sp. -21- H 8118 (Continued): SBed “l4: Coelenterata: aulooora sp. Favosites sp. (digitate type) Crinostyli, indet. Bryozoa: Fenestella sp. Bryozoa, indet. Brachiopoda: Athyris sp. Atrypa sp. (large) Cyrtina sp. Delthyris? sp. Fucrosoirifer sp. I Penta.'ner ella? sp. I 2.? sp. V Platyrachella? sp- Sieberella sp. II Stropheodonta erratica var. solidicosta Winchell ,— Bed 13: Coelenterata Favosites sp..(spheroidal coralla) PriSmatOphyllum sp. Crinostyli, indet. Brachiopoda: Platyrachella? Sp.. Bed 10: BrachiOpoda: Sieberella sp. I Trilobita: Proetus Sp. Bed 9: Coelenterata: AuIOpora? sp. Clathrodictyon cf..retiforme (Nicholson and Murie). Favosites sp. (both dumose and digitate types). Prismatophyllum sp. Crinostyli, indet. Bryozoa: Fenestella sp. BrachiOpoda: gtrzoa sp. Pentamerella? sp. I P. 7 sp. V Platyrachella? sp. Sieberella sp. II StrOpheodonta sp. -22- Fossils (Continued): Bed 8: Coelenterata?: Clathrodictyon cf. retiforme (Nicholson and Murie). Bed 7: Coelenterata?: Clathrodictyon cf. retiforme (Nicholson and Murie). BrachiOpoda: Stropheodonta sp. aff. S. demissa (Conrad) Pelecypoda: Pterinea sp. Bed 5: Coelenterata: Horn coral, indet. BrachiOpoda: 4.323111% sp. (small) Pentamerella? sp. V Pholidostrophia sp. Platyrachella? sp. Schuchertella? sp. Str0pheodonta sp. Bed 4: Brachiopoda: Atrypa sp. (large) Pentamerella? sp. aff..§. dubia Hall 2.? sp. III Bed 2: Coelenterata: Horn Coral, indet. Brachiopoda: Athyrig sp. Atrypa sp. (small) Pentamerella? sp. IV StrOpheodonta cf. erratica Winchell . Bed 1:“ Coelenterata: Aulopora sp. aff. g. serpgpg Rominger Favosites sp. (placenta type) Brachiopoda: Atrypa sp. (small) Delthyris? sp. Mucrospirifer sp. I Pentamerellg? sp. aff. g. ggpgg Hall Stropheodonta erratica var..fissicosta Winchell .2}. Locality 6 Exposures of the Killians member in road cut, NW cor., Sec. 9, T. 34 N., R. l E., and the small inlier of pre- Killians Genshaw in the ditch on south side of State High- way 33, opposite end of blind road, NEz, Sec. 8, T. 34 N., R. l E. Genshaw formation, Killians member: Bed No. Lithology 3 Limestone: black, dense, hard. 2 Shale: black, platy. Base of Killians. l Limestone: light gray, argillaceous. Total Thickness Fossils: Bed 3: Coelenterata: Horn Coral, indet. Crinostyli, indet. Brachiopoda: Chonetes sp. aff. Q. fragilis Stewart Platyrachella? sp. Fish plate, indet. Bed 2: Coelenterata: Stromatopora? sp. Bryozoa: Fenestella sp. BrachiOpoda: Atrypa sp. (large) Cyrtina alpenensis Hall and Clarke Cyrtipg sp. I Cyrtina sp. Mucrospirifer sp. I Pholidostrqphia sp. Platyrachella? sp. Productella sp. Pelecypoda, indet. Bed 1: Coelenterata: Favosites sp. (digitate type) Bryozoa: Fenestella sp. Bryozoa, indet. Thickness Feet Inches OHUIUH O\ O\ -24- Fossils (Continued): Bed 1 (Continued): BrachiOpoda: Atryoa sp. (large) Chonetgg sp. aff. Q. igggilig Stewart Cyrtina alpenensis Hall and Clarke Cyrtina sp. Mucrospirifer Sp. I Pentamerella? sp. V Pholidostrophia sp. Platyrachella? sp. Schizophoria sp. Stropheodonta cf. erratipa Winchell StrOpheodonta sp. aff. S. gemissa (Conrad) StrOpheodonta sp. Pelecypoda, indet. Trilobita: Proetus sp. Localit* Z (28) This Genshaw section is exposed below Tower Dam in Sec. 3, T. 34 N., R. l E.,along Black River. Genshaw formation: Thickness Bed No. Lithology Feet Inches 9 Limestone: light gray, shaly. 2 2 8 Limestone: dull gray, hard, shaly. l 7 Limestone: tan to light gray, irregularly bedded, argillaceous. ~ 2 4 6 Limestone: brownish gray, thick bedded, .dense, hard, bituminous. 2 6 5 Limestone: light gray, soft, poorly bedded, lower 6 inches very shaly.. 2 4 Shale: calcareous, light gray. l 3 Limestone: black, shaly. 2 6 2 Limestone: light gray, hard. 2 6 l Limestone: gray, shaly. l 4 Total Thickness l7 4 Fossils: Bed 9: Coelenterata: Clathrodictyon cf. retiforme (Nicholson and aurie) Favosites sp..(digitate type) BrachiOpoda: atrypa sp. (large) Pentamerella? sp. I -25- Fossils (Continued): Bed 8: Crinostyli, indet. Bed 6: BrachiOpoda: Atrypa sp. (large and small) Pentamerella? sp. I Platyrachella? sp. Bed 5: Coelenterata: Aulogora sp. Horn Coral, indet. Favosites sp. Crinostyli, indet.. Bryozoa: Fenestella cf. megalopora Deiss BrachiOpoda: Athyris ep. Atrypa sp. (large and small) Kucrospirifer sp. I Platyrachella? sp. Stropheodonta sp. aff. S. demissa (Conrad) é. sp. Bed 4: Coelenterata: Favosites sp. (both digitate and dumose types) Brachiopoda: Athyris sp. Atrypa sp. (large) Delthyris? sp. Mucrospirifer sp. I Pentamerella? sp. I 3.? sp. V Pholidostrophia sp. Platyrachella? sp. Productella sp. StrOpheodonta cf. erratica Winchell é. erratica var. solidicosta Winchell g. Sp. Pelecypoda: Pteriggg sp. Bed 3: Coelenterata: Aulopora sp. PrismatOphyllum sp. Bryozoa: Fenestella sp. -26.. Fossils (Continued): Bed 3 (Continued): Brachiopoda: athyris sp. AtryoS sp. (large) MucroSpirifer Sp. I Pentamerella? sp. I Pholidostrgphia sp. Platyrachella? Sp. Productella sp. Sieberella? sp. II StrOpheodonta cf. erratica Winchell S. erratica var. solidicosta Winchell S. sp. Bed 2: Coelenterata: Clathrodictyon cf. retiforme (Nicholson and Murie) Crinostyli, indet. BrachiOpoda: Sgrvpa sp. (large) Pentamerella? sp. I Platyrachella? sp. Stropheodonta sp. Trilobita: ProeSES sp. Bed 1: Coelenterata: Favosites sp. (both digitate and spheroidal coralla present) Prismatophyllum sp. Crinostyli, indet. Bryozoa: ' Fenestella sp. Bryozoa, indet. BrachiOpoda: Atrzpa Sp. (large) Delthyris? sp. MucroSpirifer Sp. I Pentamerella? sp. I 3.? Sp. VI Platyrachella? Sp. Productella sp. Schizophoria sp. Sieberella? sp. II Str0pheodonta cf. erratica Winchell S. erratica var. solidicosta Winchell S. sp. aff. S. demissa (Conrad) Pelecypoda: Pterinea? sp. -27- Locality S Exposures found at four places along the road following the center line of Sec. 34, T. 35 N., R. l E. (See Pl. I). The northernmost outcrOp is at the N. % cor., Sec..34, and extends about 100 feet south of the corner. No strata are exposed between this outcrOp and a low scarp 1,230 feet south of the N. % cor. In the scarp is exposed bed 6, which yielded only undetermined stroma- toporoids. A concealed interval extends to the base of the hill at the center of the section. (See Fig. 4). Along this hill beds 4, 5, and 6 are exposed. Bed 6 is in the Clathrodictyon-Pentamerella zone and is best exposed 1,800 feet east of the center & cor., Sec. 34. There are no outcrOps from the tOp of the hill for a distance 3,300 feet south of the N. % cor. At 3,300 feet, however, beds 7, 8, 9, 10, and 11 are seen in the roadcut. Bed 10 is a 2-foot layer of dense black limestone, typical of the Killians. A dip of 5° to the south taken on this member is the only dip measurable in Sec. 34. The relatively long distance between outcrOps and the lack of dip measurement makes interpretation of the stratigraphic relations of these outcrOps difficult. One interpretation, considered to be the more probable, is shown on Fig. 4. This figure is based on the assump- tion that the exposures lie on the southern limb of a con- centric anticlinal fold, as indicated by structural evidence 28 0.3.54 053de oceans—.3 human 'mflnulu. ..v meGC 0;] o . “0.30m Huacouuhox J W :3: o coupgomwdxm duodenum, a m .13 546021066 60:43 on [Ir amoo f .w& ...v \ 1"‘Iu 9o... . ova 0... Ac .3» a» “Mafiaou .\ WWWVBA“. » \“m ears»! 04.3. I VFL ( .- ‘3 \ “Lo 5%qu \ $.ka . O my: ANWA‘L‘WNN. : u \ i a . o .. m m 9 1. -28- from outside of Sec. 34. (See Pl. III). The thickness of the beds based upon the cross—section is 101 feet. Bed 10 is the Killians limestone, although the exposed section is thin. Thus there would be 97 feet of strata, exposed and concealed, between the Killians exposure and the N. % cor. of Sec. 34. This would make the calculated elevation on the top of the Rockport 733 feet at the N. % cor., Sec. 34, T. 35 N., R. l E. (See Pl. III). An ele- vation of 720 feet is more compatible with structural evi- dence (see discussion below); consequently, Fig. 4 may represent an interpretation having 13 feet of possible error. Another interpretation is shown on the correla- tion chart (Fig..5). In this figure the outcrops are as- sumed to represent rocks lying directly on each other from north to south. This latter interpretation is considered to be less plausible than the former, for structural evi- dence is lacking, since the tOp of the Rockport would be found at an impossible elevation on the basis of the local structure. Furthermore, fossils collected from the N. % cor., are those found elsewhere in the lower third of the Genshaw, and only the placing of this section on the limb of an anticline would allow this outcrOp to occupy its prOper_Stratigraphic position. -29- Locality § (Continued) Genshaw formation, Killians member: Thickness Bed No. LitholOgy Feet Inches 11 Limestone: light gray, shaly. l 10 Limestone: black, dense, almost litho- graphic. Base of Killians. 9 Shale: light gray, calcareous. "Chonetes zone of Fig. 4. Shale: light gray, calcareous, "Cyrtina zone". Limestone: black, shaly. Covered interval. (Estimated). Limestone: gray, shaly, poorly ex- posed. Contains thin gray shale layers. (Pentamerella-Clathrodictyon zone". Limestone: massive, light gray. Limestone: light gray, very shaly. Covered interval.. Limestone: gray, argillaceous. Covered interval. (Estimated). Limestone: dark gray to black, dense. Shale: light gray, calcareous. Total Thickness O‘\ R] CO [0 l-‘ U'H'D-P' 42' h) H PM K)! #‘U'l H Hm #U‘I O\Ull\>\NU1 O\ }_J O Fossils: Bed 10: Coelenterata: Horn coral, indet., Prismatgphyllum sp. BrachiOpoda: Athvris sp.. Atrypa sp. (large) gyrtina alpenensis Hall and Clarke PholidostrOphia sp. Platyrachella? sp. Cephalopoda: Gomphoceras? sp. Trilobita: Proetus sp. Fish plate, indet. Bed 9: Coelenterata: Favosites sp. (digitate and dumose types) Bryozoa: Fenestella sp. Bryozoa, indet. -30- Fossils (Continued): Bed 9 (Continued): BrachiOpoda: gthyris sp. Atrypa sp. Chonetes sp..aff. Q. fragilig Stewart Czrting Sp. Mucrospirifer sp. I Pholidostrophia sp. Platyrachella? sp. Egoductella sp. StrOpheodonta erratica var. solidicosta Winchell g..sp. Ostracoda, indet. Bed 8: Brachiopoda: Atrypa sp. Cyrtina alpenensis Hall and Clarke Cyrtina hamiltonensis Hall Cyrtina sp. I Cyrtina sp. Mucrospirifer sp. I Pholidostrophia sp. Platyrachella? sp. Strgpheodonta cf. erratica Winchell S. sp. aff. g. concava Hall §. sp. aff. §. demissa (Conrad) S. sp. Bed 6: Coelenterata: Clathrodictyon cf. retiforme (Nicholson and Murie) Brachiopoda: Cyrtina alpenensis Hall Pentamerella? sp. I 3.? sp. III 2.? sp. V 2.? sp. VI Platyrachella? sp. Trilobita: Proetus sp. Bed 4: Coelenterata: Clathrodictyon cf. retiforme (Nicholson and Murie) Favosites sp. (digitate type) PrismatOphyllum sp. Crinostyli, indet. Bryozoa: Fenestella sp. -31.. Fossilg (Continued): Bed 4 (Continued): Brachiopoda: Atrypa sp. gyrtina hamiltonensis Hall Pentamerella? sp. V 2.? Sp. VI - Platyrachella? sp. Productella sp. Stropheodonta sp. Bed 3: Coelenterata: StromatOpora sp. (large, widely-spaced mamelons) Bed 2: BrachiOpoda: Mucrospirifer sp. I Pholidostrophia sp. Platyrachella? sp. Pelecypod, indet. Bed 1: BrachiOpoda: Athyrgg sp. Atryog sp. Choneteg sp. aff. S. fragilis Stewart gyrtina alpenensis Hall and Clarke Mucrospirifer? sp. Mucrospirifer sp. II Pentamerella? sp..aff. 2. dubig Hall 2.? sp. III 2.? sp. IV Pholidostrgphia sp. Platyrachella? sp. Schizophoria sp. Stropheodonta erratica var..fissicosta Winchell S..erratica var. solidicosta Winchell S. sp. Pelecypoda: Pterinea sp. Indet. (Glyptodesma type) Trilobita: Proetus sp. Fish plate, indet. Locality 2 Section exposed at the base of the ridge, known locally as Limestone Hill, on the western line of Sec. 22, T. 35 h., R. l E., 1,780 feet north of the SW cor. OutcrOp begins about 10 feet above the base of the Genshaw formation. -32- Locality 2 (Continued) Genshaw formation: Thickness Bed Ho. Lithology Feet Inches 2 Limestone: light to dark gray, poorly bedded. 5 l Limestone: light gray, shaly. Poorly exposed. 8 Total Thickness l3 Egssils Bed 2: Coelenterata: StromatOpora?sp. (large, widely Spaced mamelons) Crinostyli, indet. Bryozoa, indet. Brachiopoda: Atrypa sp. Cyrting sp. StrOpheodonta sp. Pelecypoda, indet. Trilobita, indet. Bed 1: Coelenterata: Prismatophyllum sp. StromatOpora? sp. (large, widely Spaced mamelons) Crinostyli, indet. BrachiOpoda: Pentamerella? sp. VI Platyrachella? sp. StrOpheodonta sp. Legal. .Lit‘ i. Top of the sub-Killians as well as the Killians member of the Genshaw formation found in low cuestas in the NEi, SW3, Sec. 36, T. 35 N., R. l 5., two and a half miles northeast of Tower. Genshaw formation, Killians member: Thickness Bed No. Lithology Feet Inches 3 Limestone: black, dense, shaly layers 4 6 2 Shale: black, calcareous. Base of f Killians member. 7 l Limestone: light gray to black, argil- laceous. 7 Total Thickness 19 .3}. Locality LS (Continued) Fossils: Bed 3: Coelenterata: Favosites sp. (spheroidal corallum) Bryozoa, indet. CephalOpoda: Gomphoceras sp. Bed 2: Coelenterata: AulacOphyllum Sp. Favosites sp. (digitate type) Prismatophyllum sp. Stromatoporfl'sp. (large, widely Spaced mamelons) Crinostyli, indet. Bryozoa: Fenestella sp. BrachiOpoda: Athzris Sp. Sgrzpa sp. (large) Mucrospirifer sp. I Pholidostrophia sp. Platyrachella? sp. Productella sp. Schizophoria sp. Schuchertella? Sp. Stropheodonta sp. Pelecypoda, indet. Trilobita: Proetus sp. Fish plate, indet. Bed 1: Coelenterata: Prismatophyllum Sp. Stromatopora? sp. (small mamelons) Crinostyli, indet. BrachiOpoda: SSrypa sp. (large) Chonetes sp. aff. S. fragilis Stewart Cyrtina alpenensis Hall and Clarke S. sp. I Delthyris? sp. I Mucrospirifer sp. I Pentamerella? sp. VI Platyrachella? sp. -34- Localit 2; (29) Composite section of the Ferron Point and the lowest beds of the Genshaw obtained from the exposures in the abandoned quarry of the Cnaway Limestone Co. at Black Lake and in the cliff along the southern shore of the lake, in Sec. 7, T. 35 N., R..2 E.. The fauna from the Ferron Point formation is the best preserved of any in the area of study. Genshaw formation: Thickness Bed No. Lithology Feet Inches 4 Limestone: dense, gray, slightly argil- laceous. 7 3 Limestone: dense, light gray, thick- and well-bedded. 3 2 Limestone: dense, massive, thick- bedded. Many overturned coralla of PrismatOphyllum sp.. Base of Genshaw. 6 6 Ferron Point formation: 1 Shale: greenish-gray, thin-bedded, plastic, intercalated limestone layers. 9 Total Thickness 25 0\ TOp of Rockport Quarry formation. Fossils: Bed 4: Coelenterata: Prismatqphyllum sp. BrachiOpoda: Pentamerella? sp. III 2.? Sp. IV Bed 2: Coelenterata: Prismatophyllum sp. Stromatgpora? sp. (very small, closely Spaced mamelons) Crinostyli, indet. BrachiOpoda: Sieberella sp. I Bed 1: Coelenterata: Aulogora sp. aff. S. serpens Rominger Cystiphyllum sp. Favosites sp. (digitate type) Horn coral, indet. PrismatOphyllum sp. -35- Fossils (Continued): Bed 1 (Continued): Echinoderma: Crinostyli: CF6 cf. A Davies CC cf. 2 Davies CC cf. 4 Davies CC7A Davies 0C3 cf. A Davies CC indet. Davies Bryozoa: Fenestella Sp. Bryozoa, indet. BrachiOpoda: Athyris sp. Atrypa sp. (small) Chonetes sp. aff. coronatus (Conrad) S. sp. aff. S. fragilis Stewart Delthyris? sp. Nucrospirifer sp. I 5. sp. II - Pentamerella? cf. pavilionensis Hall Schuchertella sp. Pelecypoda, indet. Pelecypoda: Pterinea cf. flabellum (Conrad) CastrOpoda7: Tentaculites Sp..aff. gyracanthus (Eaton) 2. cf. scalariformis Hall Trilobita: Proetus sp. I (small) 2. sp. (large) Locality SS Intermittent exposures of the Genshaw found along an escarp- ment trending approximately east-west in the 83%, Sec. 25, T. 35 N., R. 1 E. Best exposed along road 1,100 feet south of the W% cor., extending in escarpment to the E% cor., Sec. 30, T. 35 N., R. 2 E. Genshaw formation: Thickness Bed No. Lithology Feet Inches ’ 5 Limestone: gray, shaly. 2 4 Limestone: gray, argillaceous. 5 3 Limestone: light gray, shaly. 2 6 2 Limestone: dark gray to black, poorly bedded, dense. 2 6 1 Limestone: dark gray, dense, unevenly bedded. 10 Total ThICKness 22 Locality 22 (Continued) §9§§ll§3 Bed 5: Coelenterata: Stromatopora? sp..(1arge, widely spaced mamelons) Bed 4: Coelenterata: Prismatophyllum sp. Crinostyli, indet. Bed 3: Coelenterata: PrismatOphyllum sp. Bed 1: Coelenterata: Favosites sp. Prismatophyllum sp. StromatOpora? sp. (small, closely Spaced mamelons) BrachiOpoda: Atryoa sp. Cyrtina sp. Pentamerella? sp. Platyrachella? sp. StrOpheodonta Sp. Locality 23 Section obtained by traverse run from 1,330 feet east of center, Sec. 32, past Rowe School to last Genshaw outcrOp 1,400 feet north of w.% cor., Sec. 29, T. 35 N., B. 2 E. Exposures are found intermittently along low escarpment trend- ing N. 40° W. This section also includes one small exposure which is 1,580 feet north of the last-named Genshaw outcrOp in Sec. 29; found along the highway. Genshaw formation: Thickness Bed Kc. Lithology Feet Inches 7 Limestone: dark gray, thin-bedded. 2 Concealed interval. 7 6 Shale: calcareous, light gray. l 5 Limestone: light to dark gray, massive. 2 6 4 Limestone: tannish gray and shaly at top, grades into light gray, thin-bedded at base. "Clathrodictycn zone"._ Concealed interval. 3 Limestone: gray, massive, dense. NU‘I-xl -37- Locality 23 (Continued) Genshaw formation: Bed No. Lithology 2 Limestone: light gray, shaly, thin- bedded Concealed interval. 1 Limestone: massive, well-bedded, dark gray, shaly at base. Total Thickness Horn corals, indet. Crinostyli, indet. Bryozoa, indet. BrachiOpoda: Atryoa Sp. Pentamerella? sp. I Platyrachella? sp. Strgpheodonta sp. Bed 6: BrachiOpoda: Pentamerella?sp. V 'Bed 5: Coelenterata: Thickness Feet Inches \OKN COR) ON StromatOpora? sp. (small, widely spaced mamelons) Bryozoa: . Fenestella sp BrachiOpoda: Athyris sp. Sgryoa sp. Mucrospirifer sp..I Pentamerella? sp. 2. sp. I - Pholidostrophia sp. Platyrachella? sp. Bed 4: Coelenterata: Clathrodictyon cf. retiforme (Nicholson and Murie) Prismatophyllum Sp. BrachiOpoda: Platyrachella? sp. Strgpheodonta Sp..aff. S..demissa (Conrad) S. Sp. Pelecypoda, indet.. Fossils (Continued): Bed 1: Coelenterata: Favosites Sp. (dumose type) Brachiopoda: Atrypg sp. hucrospirifer Sp. I Pholidostrophia sp. Platyrachella? Sp. Stropheodonta sp. 29cality 24 Books exposed 180 feet south of SE cor., Sec. 30, T. 35 3., B. 2 E., one and one-half miles north of Onaway. Not shown on the correlation chart, Fig. 5. The upper two beds, beds 2 and 3 below, are probably the lower part of the Newton Creek limestone. The fossils contained are so different from those found in the top of the subjacent Killians mem- ber, bed 1 below, that the writer did not study them.. Dr. G. A. COOper of the U. ”. National Museum is examining this faunule to determine whether or not it is typical of the Newton Creek.. Genshaw formation, Newton Creek limestone member: Thickness Bed No. Lithology Feet Inches 3 Limestone: tan to brown, crystalline, dense, hard. 1 2 Limestone: light tannish-gray, pure, dense, crystalline.) Base of Newton Creek. 1 Killians member: 1 Limestone: black, bituminous, shaly.. 2 Total Thickness 4 Egssils: Bed 1: Coelenterata: Favosites sp. Crinostyli, indet. Bryozoa, indet.. BrachiOpoda: Athyris Sp. Atrypg sp. Pentamerella? sp. V Platyrachella? sp. Pholidostrophia sp. Productella sp. SchiZOphoria sp. Sieberella?sp..II Stropheodonta sp. -39- 29cality 2S Ledges of Killians limestone below water level on Upper Black River in 3%, Sec. 13, T. 34 N., R. 2 E. No collec- tions were made. Locality 2S Section obtained by study of the samples of the exploratory well, Campbell No. l, drilled in 8%, N32, Sec..7, T. 34 N., R. 1 W. The detailed descriptions are limited to the Gen- shaw and Ferron Point formations, but the general lithOIOgy and thickness of the overlying and underlying formations is also given. Elevation at surface, 847 feet above sea level. Formation LithOlOBY Thickness Depth Glacial_drift 25 25 Gravel Point Gorbut member Grey and black limestone 15 40 Koehler Buff and gray limestone 60 100 Genshaw Killians member Limestone: dark gray, argillaceous. 5 105 Limestone: gray porous, and black lamin- ated.- Pyrite. Fossil fragments. 5 110 Limestone: black, shaly. Bryozoa. 5 115 Limestone: black. Pyrite.. Bryozoa, crinostyli.. 5 120 Limestone: black to light gray argil- laceous with a little brown dolomite. Crinostyli, bryozoa, gastrOpod. Pyrite. 10 130 Total thickness, Killians 30 feet Limestone: light to dark gray, argil- laceous. Crinostyli, Tentaculites sp., brachiopods. 5 135 Limestone: hard, dense, argillaceous, buff; some grey dolomitic. Bryozoa. 10 145 Limestone: light gray, argillaceous. 5 150 Limestone: light gray, shaly. 15 165 Limestone: gray to white, calcite crys- tals.. Crinostyli, brachiOpods, bryozca. Some pyrite. 5 170 Limestone: light gray shaly. Pyrite. Crinostyli, Tentaculites sp., Bryozoa. 15 185 Limestone: gray, argillaceous. Pyrite. Crinostyli, Cyrtina? sp., bryozoa. 15 200 -40- Formation Lithology Thickness Depth Genshaw (pre-Killians, Continued) Limestone: gray, black streaked, dense. Pyrite, bryozoa, Tentaculites sp., brachiopods. 5 205 Limestone: gray, argillaceous. Crino— styli, Stropheodonta? sp. 5 210 Limestone: gray, dense, argillaceous. White calcite fragments. Crinostyli and brachiopod fragments. 10 220 Limestone: dark gray, shaly, bitum- inous streaks.. Pyrite, bryozoa and an ostracod. Limestone: dark gray. Calcite crys- tals. Crinostyli, bryozoa, Tentacu- lites sp. 5 230 Limestone: gray, dense, argillaceous. Pyrite. Bryozoa, crinostyli, ostracod. 10 240 Limestone: dark gray, argillaceous. Calcite and pyrite crystals. Crino- styli, bryozoa. 8 248 Total thickness of Genshaw (including Killians) 148 225 U] Ferron Point Shale: calcareous, light gray, soft, plastic when wet. Fragments of brachio- pods; crinostyli. Z 255 Rockport Qparry Limestone: buff, lithographic at tOp, stylolitic; lower 20 feet is black, bi- tuminousL some dolomitic. 50 305 Bell shale Dark gray, limy shale. Pyritiferous. Crinostyli abundant.. 90 395 TOp of Dundee limestone. SISTEMATIC DESCRIPTICHS CF FCSSILS Phylum BRACHIOPCDA Order PRCTREMATA Beecher Genus CHCNETES Fischer de Waldheim 1837 The observed characteristics of the Genshaw and Ferron Point representatives of this genus coincide with Weller's description. (1914, pp. 78-79. Also consulted was Hall and Clarke, 1892, p. 303). Two Species of the genus are recognizable; each has a limited stratigraphic range. Chonetes aff. g. fragilis Stewart 1927 Chonetes fragilis Stewart, Ohio Geol. Survey; 4th Ser., Bull. 52, 1927, pp‘BS-BQO Description.--Shell concavo-convex; swéemicircular in out- line; small---dimensions of average specimen: length, 10 mm., width, 13 mm., thickness, 3 mma Greatest width at mid- length of shell, but some specimens exhibit an extended ‘hinge line which makes the shell mucronate with hinge-line width equal to greatest breadth of valves. Ventral valve gently convex with rounded apex near or slightly anterior to center of valve; postero-lateral region somewhat flattened. Concave cardinal area narrow, making a small angle with the plane of valve, postero-lateral margins of cardinal area bear about five spines at oblique angles. Triangular del- thyrium small and closed by a sharply convex deltidium. Small papillae on inner surface of ventral valve. Dorsal valve concave, concentric with inner sur- face of ventral valve; cardinal area narrow--less than 1 mm. wide. Surface of both valves finely multicostellate; fine, low, rounded costellae are crossed by concentric growth lines; costellae number 16 in 5 mm. on ventral valve 5 mm. from beak. Bifurcation common on anterior half of shell. Remarks.--§. aff. g. fragilis closely resembles g. fragilis Stewart from the Silica shale of Ohio, but Dr. G. H..Ehlers of the Museum of Paleontology at the University of Michigan has compared the Genshaw forms with topotypes of g..fragilis and states that the ”...Genshaw specimens have more rounded cos- tellae than typical examples of C. fragilis; they probably belong to a distinct species. There are a very few small shells in the Sil- ica shale which resemble the Genshaw speci- mens in respect to the rounded character of the costellae; they differ from the latter, however, in being relatively wider." (Ehlers, 1942, Personal Communication.) These observations were confirmed by the writer after com- parison of the Ferron Point and Genshaw forms with tOpotypes of Q. fragilis in the possession of the Geology Department at Michigan State College. This species was found at several localities occu- pying positions in the transitional beds at the base of the Killians member and in a zone about 95 feet lower, in the Ferron Point formation. This is the form from which the "Chonetes zone," best exposed in Sec. 34, north of Tower, derives its name because of the abundant and consistent occurrence of these forms. Several specimens of Q..aff..g..fragilis were col- lected from beds at the N. % cor., Sec. 34, north of Tower, and from the Ferron Point at Black Lake. This, then, is a recurrent form.. Chonetes aff. Q. coronatus (Conrad) 1842 Strgphomena carinata Conrad, Jour..Acad. Nat. Sci., Phila- delphia, vol. 8, 1842, p. 257, pl..14, fig. 13. (Not avail- able for reference.) Chonetes coronatus Prosser, Md. Geol. Surv., Middle and Upper Dev., 1913, p. 148, pl. 11, figs. 18-21. Chonetes coronatus Stewart, Ohio Geol. Survey, 4th Ser., Bull..32, 1927, pp..37-38. Description.--This species differs from g. aff. Q. frarilis in: being larger, with average dimensions: length, 13 mm., width, 18 mm., estimated thickness, 3 mm.; in having fewer (12) and larger costellae in 5 mm. at distance of 5 mm. from beak instead of 16 as in g. aff. g..frarilis; in having more spines on each side of beak (6 or 7); and in having more and much coarser papillae on the interior of the ventral valve. Remarks.--Comparison of this Ferron Point form with g. coronatus from the Silica shale of Ohio shows the Cheboy- gan and Presque Isle County form to be much more finely costellate, and much thinner, although the two are similar in size. Miss Grace Stewart, who has identified Q..coronatus from the Silica shale states: "The large specimens have slightly stronger striations than is usual in the species,..." (Stewart, op..cit., p. 38.) This statement would indicate that the Ferron Point ghggetes may be quite as near Q. coronatus from the New York Hamilton as the Silica shale forms, differing chiefly in being thinner. The characteristic shallow undefined sulcus along the middle of the ventral valve is faint in some of the Specimens collected from the Ferron Point formation. Genus ENTAMERELLA Hall 1867 The generic status of the following described 8 members of the genus Pentamerella is not firmly established. Hall (1867, p..373) established the genus, but later investi- gations (Hall and Clarke, 1894, p. 245) showed the necessity for additional diagnostic features. Schuchert and COOper (1932, pp. 171-177) added further diagnostic criteria, but it is still difficult to separate the genera Pentamerella, Sieberella, and Gyoidula. COOper (1942, Personal Communication) states that he has seen forms with a "rectimarginate anterior commissure" and others "with a slight flexure developed in a ventral direction." The Genshaw forms show a slight flexure in a dorsal direction, but all other diagnostic criteria described by Schuchert and Cooper are observed in the forms studied by the writer. COOper believes that his species is more like Pentamerella in its ornamentation than true Gypidula. He indicates his intention of calling the form Pentamereglg? in his own work. The same terminology will be followed here. A portion of Schuchert and Cooper's generic de- scription upon which the determinations are based is quoted below: "Exterior.--Outline subtriangular to subpent- agonal; hinge-line narrow; cardinal extremi- ties rounded; lateral profile biconvex, the ventral valve having the greater convexity.. Anterior commissure uniplicate; dorsal fold usually low, in some species nearly obsolete. Ventral interarea narrow, curved, apsacline, beak incurved strongly, umbo swollen; delthyr- ium with incipient deltidial plates. Dorsal interarea obsolete, beak curved under that of the ventral valve. Surface usually multi- costate, occasionally smooth. Shell substance fibrous, impunctate. "Ventral interior.--Teeth narrow and sharp; spondylium duplex shallow;...septum short.... "Dorsal interior.--Netothyrial cavity deep; plates supporting brachial processes broad and flat, supported by thin curved plates which unite in the mid-line of the shell to form a cruralium that in some specimens is supported by a low duplex septum...." (Schuchert and Cooper, 1932, p. 176). Pentamerella? sp. I Description.--Ovate to subtriangular in outline; biconvex, ventral valve exhibiting greater convexity. Length equal to width or slightly greater; thickness two-thirds to three- quarters times the length. Dimensions of a large specimen: length and width, each 39 mm.,.thickness, 31 mm.; the forms vary but little from these dimensions. Ventral valve flattened in mesial area; steep umbonal flanks, gentler slope toward anterior. An incipient fold appears to be present on anterior half of ventral valve of some shells; anterior commissure shows slight flexure in the dorsal direction¢.. Beak very strongly in-- curved, obscuring foramen and overlapping beak of opposite valve.. Cardinal area small, concave, and narrow; concavity variable in degree. Posterior half of umbo faintly plicate, beak smooth; anterior half of umbo and remainder of valve covered by costae, 26 to 30 in number; 8 costae on fold of specimen with 30 costae. Internally, the V-shaped spondylim has short supporting septum- Dorsal valve convex with prominent rounded umbonal ridge; greatest depth posterior to mid-length of valve. Dor- sal fold, faint on some specimens, on anterior two-thirds of valve. Internally, the septal plates converge downward, uniting to form a single septum which is attached to the inner surface of the dorsal valve in a single straight line. The upper septa join the "thin curved plates" of Schuchert and Cooper. Remarks.-—The dorsal fold is of generic significance since it is the only criterion for distinguishing Pentamerella? from Sieberella. These specimens are more heavily costate and much larger than any of the other species of Pentamerella? found in the Genshaw., There is some variation in the form of specimens, even from the same bed, as well as in the num- ber of plications, in the steepness of the umbonal lepes, and in the convexity of the dorsal valve. Pentamerella? sp. I is limited to the Genshaw beds below the Killians and occurs in greater abundance than any other form of the Pentameracea. The best specimens were collected at Rainy River Falls which is three and a half miles northeast of Onaway. Good specimens were also found at the exposure at Tower Dam. Pentamerella? Sp. aff. 2. dubia Hall 1860 Spirifer dubius, Hall, 13th Hept., N. Y. State Cab. Kat. HiSto, 1860, p090 Pentamerella dubia, Hall, Pal. of New York, vol. IV, 1867, p. 379, pl. LVIII. Pentamerella dubia, Hall and Clarke, Pal. of New York, vol. VIII, 1894, pl..LKXI, figs. 32-37. Description.--Shell subtriangular in outline; biconvex, con- vexity of valves nearly equal; umbo of dorsal valve swollen. Dimensions of average specimen: length 22 mm., width, 20 mm., thickness, 15 mm. Both ventral sulcus and dorsal fold nearly obsolete and slightly unsymmetrical. There are 16 costae on anterior border of ventral valve, 4 of which are in sul- cus. Interior not seen, but worn exterior of a dorsal valve indicates convergence of septa to join inner surface in a single straight line. Hemarks.--Most of these specimens are poorly preserved. They differ from g.? Sp. I in their much smaller size, in having faint costae and these only on anterior extremity of shell, and in being longer than wide.. This form resembles g. 2gpgg. (Hall, 1860, p. 90; Hall, 1867, p..379, pl. LVLU; figs. 38 and 39, p93 40-43; Hall and Clarke, 1894, p. 242 and 245, pl. LXXI, figs. 34 and 35, pg; 32-33, 36-38.) The only dif- ference is that the dorsal valve of the Genshaw forms is relatively longer. not all of hall‘s figures illustrate specimens similar to those found in the Genshaw; only those figures named above do, but Hall's written descriptions do cover the senshaw forms.. This Species is limited to the lower 20 feet of the Genshaw. Pentamerella? Sp. III Description.--Shell subovate in outline; biconvex, ventral conveXity mucn greater. Dimensions of an average specimen: length, 23 mm.; width, 23 mm.; thiCkness, 16 mm. insipient deltidial plates not Observed, but these forms were referred to Pentamerella? because of the dorsal fold. The dorsal fold is weak, as is the sulcus in the ventral valve. Eighteen faint costae occur on anterior half of shell; umbo smooth; 5 costae on fold._ RemarkS.--§.? sp..lll has all the characteristics of 3.? sp. aff. g..dubia except that it has a somewhat less prominent dorsal umbo, a more obtuse umbonal angle, and a nearly ovate outline.. Part of the original Shell material is preserved in most SpeCimens.. ‘ These forms are found in greatest numbers in the lower 20 feet of the Genshaw, but some are found as high as 60 feet above the base. Pentamerelgg? sp..lV Description.--Ventral valve subtriangular to subpentagonal in outline; ventral valve convex, beak incurved.. mo dorsal valves available for study. Length Slightly more than width. Dimensions of average ventral valve: length, 20 mm., width 24 mm., thiCkness 13 mm.. no sulcus or feld.. Sixteen broad rounded.costae, very faint on some specimens.. Slightly con- cave interarea. ventral interior snows Sharp, anteriorly directed teeth.. Remarks.--0nly 3 ventral valves, each irom a different local- ity, are available for study.. These are referred to the genus With neSitancy because they lack the ventral fold that would place them in Sieberella. The other genus to which they might be referred is avoidula, and Since diagnostic Characters Of that genus are found only in the dorsal valve, it cannot be proved that these forms are not of expidula. These ventral valves differ from £.? Sp..aff. Em dubia in being larger, in haVing a Slightly wider umbonal angle, in‘ having coarser costae, and lacxing any trace of a sulcus- 3.? Sp. lv differs from 5.? sp..lll in its more nearly tri- angular outline, in being more coarsely plicate---only 7 costae in l5 mm., as against 9 in 15 mm. on §.? sp..lll--- and in naVing a smaller umbonal angle. There is some varia- tion in the degree of flattening of the umoo in these forms. These Specimens indicate that 5.? sp. lv is limited to the lower 20 feet of the Censnaw.. Pentamerella? sp..V ggmarks.--These forms are large, multicostate, differing from 5.? sp. I in haVing mucn flatter valves with resultant decrease in thibkness and in being coarsely and very irregu- larly costate.. Dimensions of an average speCimen: length 38 mm., width 31 mm., tnicxness 24 mm. lnd1v1dual varia- tions of this spebies are numerous, but the normal tendency is for bifurcation to occur on the crest of the umbo. This form is limited to the middle and upper parts of the Genshaw, the lowest occurrence being about 20 feet above the base. Pentamerella? sp. VI Eemarks.--This species is represented by only 5 ventral valves, 4 of which are fragmentary. The observed characters, however, are those of 2.? Sp. 1 with the exception that the ventral valve has a more convex umbo, contrasting sharply with the flattened umbo of g.? sp. 1. All Specimens occur in the middle Genshaw with the exception of one which is from the top of the formation.. Pentamerella? cf. pavilionenSis hall 1867, Pentamerella papilionensis hall, Pal. of New York, vol. lv, part l, 1867, pp. BYI-BI8, pl. 58, figs. 28-37. Pentamerella pavilionensis Hall and Clarke, Pal..of New York, vol. 8, part ll, l894, p..245. RemarkS.--This species possesses the ornamentation, size, and conspicuous dorsal fold of g. pavilionensis as described by hall. It differs in being triangular in outline, not sub- ovate. This form was found in the Ferron Point formation in the exposures at Black Lake.. Several specimens from the Ferron Point formation in the Rockport Quarry in Alpena County closely resemble the Black Lake forms. §.? cf. pavil- ionensis is limited to the Ferron Point in Cheboygan and western Presque lsle counties. Genus PhOLlDOSTROPulA hall and Clarke 1594 rholidostrophia sp. Description.--Several specimens from various positions in the stratigraphic column are placed in the genus rnolidostro- phia (hall, lool,.pp..lU4-l05; hall and Clarke, l692, p..2o7) because of the following observed Characteristics: shell semi-circular to semi-elliptical in outline; concavo-convex; greatest width at about mid-length of valve. Dimensions of an average-size specimen: length, l5 mm.; width, 19 mm.; thickness, 4 mm.. hinge line denticulate, ends rounded. ven- tral valve has low convexity, but in degree this feature-is variable in the specimens studied; beak small and protrudes slightly; cardinal area narrow; delthyrium closed. Dorsal valve concave, paralleling inner surface of ventral; beak minute. Ventral interior pustulose; exhibits a very low double ridge separating the muscle scars whicn cover more than half of shell; muscle scars deeply impressed, narrow at posterior, widening toward anterior margin.. Dorsal in- terior not observed. Shell thin and fragile; smooth, except for fine growth lines; invariably nacreous. Remarks.~-No attempt is made to determine the specific status of the members of this genus found in the eensnaw and Ferron Point formations. The characteristics of Specific value in this genus are so few and difficult of observation that identifications Should be made by comparing forms with the original type specimens. The only two features of a variable nature in the forms studied are convexity of the ventral valve and size. These were found to be of no value for stratigraphic purposes. Genus PRCDUCTELLA hall 1807 Productella sp. Remarks.--Undifferentiated species of this genus occur in relatively small numbers in the Genshaw formation. The specimens collected exhibit the typical Characteristics of the genus as described by heller (1914, Text, pp. 97-90) and mail \1501, p. 153).. The Genshaw forms collected are in a poor state of preservation and this, combined with their scarcity, renders them of little stratigraphic value. The shells are small,.deeply concavo-convex, with straight hinge- line, narrow cardinal area, closed delthyrium. The ventral exterior is irregularly Spinose. Genus SChlLOPHORlA King 1650 Schizophoria sp. Description.--about a score of Specimens of this genus, (hall and Clarke, 1692, pp. 211-213; Weller, Stuart, 1914, pp. 161-162) many badly crushed, were found in the Ferron Point and Genshaw formations.. Their general characters are described below: shell subcircular in outline; dorsi- biconvex; Shallow sulcus on anterior half of ventral valve widening toward anterior margin Where its width is equal to one-half width of valve. Greatest width about at mid- length of Shell, cardinal extremities rounded. Ventral beak short, rounded, and flat.. Deep muscle scars on floor of the ventral valve are subovate in outline. These scars are bordered on the lateral margins by sharp, narrow ridges, and are divided by a mucn coarser rounded ridge between the two depressions. Dorsal interior not seen. Surface highly multicostellate. RemarkS.--Because of the crushing and the fact that speci- mens are few in number, they do not warrant attempts at specific identification.. The stratigraphic range of the genus is from the Ferron BOint through the hillians member, although the greatest number of specimens came from the Genshaw Just below or definitely within the hillians member. The Specimens are from several localities. Genus SIEBERELLA Oehlert 1887 Generic description of Schuchert and Cooper (1932, . 175): p "Description.--Exterior.--Outline galeatiform as in Gypidula, hinge—line fairly arcuate; car- dinal extremities rounded. Lateral profile biconvex, the ventral valve usually with the greater convexity.. Anterior commissure sul- cate; ventral fold usually defined only on ‘the front half of the shell.. Ventral inter- area rather wide for the sub-family, curved, apsacline, delthyrium Open, beak incurved, umbo swollen. Surface multicostate; shell substance fibrous, impunctate. "Ventgg; interior.--Like Gzpidula. (idem.. p. 174: Delthyrial cavity deep; teeth strong, narrow, elongate; dental plates convergent, forming a narrow spondylium, supported by a duplex septum for part of its length; free at the front end.. Septum Short.) "Dorsal interior.--The tripartite character of the cardinalia is essentially the same as that of Gzpidula, but the septal plates, in- stead of uniting directly with the floor of the valve, unite with a low median septum." Sieberella sp. I Description.--Subtriangular in outline; longer than wide, although a few Specimens are slightly wider than long, making them subovate; biconvex, although dorsal valve nearly flat. Dimensions of a small Specimen: length, 40 mm..(approxi- mated); width, 42 mm.; thickness, 30 mm., of which 24 mm. is thickness of ventral valve alone. Dimensions of largest specimen: length, 53 mm; width, 45 mm.; thickness, at least 30 mm., although these dimensions were modified some- what by crushing.. Ventral valve convex, semicircular in outline from side view. Faint fold on anterior three-quarters of shell serves to establish generic status.- Anterior commissure sulcate ventrally, beak recurved to cover dorsal beak and obscure foramen., Umbo narrow, tapers fast posteriorly; umbonal slopes steep from narrow crest. Cardinal area very small and invisible in complete specimens.. Shell multicos- tate except on posterior extremity of beak; costae 22 to 28 in number at anterior margin; bifurcation common but at variable distances from beak; coarsest costae are in median region of the valve.. Internally as in foregoing description of Schuchert and Cooper; only the septum and spondylium were observed. Dorsal valve nearly flat, but posterior one-third curves up strongly beneath the ventral beak to give illusion of convexity. Umbo slightly raised; in some forms definitely depressed. Wide, shallow, anterior sulcus on all Specimens. Dorsal interior as in Pentamerella? sp. I above. Remarks.--This Species is easily distinguished from all other Pentameracea in the Genshaw by its wide, shallow dorsal sul- cus and its narrow, fast-tapering umbo and beak.. The generic distinction between Sieberella and gentamerella as given by Schuchert and Cooper was observed; viz.: Pentamerellg has a dorsal fold, while Sieberella has a sulcus on the dorsal valve. Their internal structures are usually alike. This form occurs sparingly in the lower half of the Genshaw. Lowest occurrence is very near the base; highest about 50 feet above base. Sieberella? sp..II Remarks.e-Several Pentamerids are doubtfully assigned to Sieberella because of a faint fold on the ventral valve. §.? sp..II differs from all other Pentamerella and Sieberella in the Genshaw by having a wide hinge line. Only ventral valves of the Species were found.. This form ranges from 45 to 60 feet above the base of the Genshaw but is not very common. Genus STROPHECDONTA Hall 1852 StrOpheodonta sp.. Many fragmentary and poorly preserved specimens from several localities are here referred to Stropheodonta sp. 'Most forms are small and exhibit the generic character- istics (Hall and Clarke, 1892, pp. 284-293). but no attempt was made to determine their specific statusa Other Speci- mens, better preserved, are described briefly below. Stropheodonta cf. erratica Winchell StrOpheodonta erratica Winchell, The Grand Traverse Region, Ann Arbor, Mich., Dr. Chase's Steam Printing House, 1866, p. 93. (Not available for reference.) Stropheodonta erratica, Ehlers and Kline, Contr. Mus. Pal., Univ. of Michigan, vol..l4, no. 10, 1934, pp. 150-151; pl. 1, figs. 4-9. Remarks.--The forms from the Genshaw formation are compared to §..erratica after examination of plastocotypes in the possession of the Department of Geology at Michigan State College. The Genshaw specimens are commonly larger than Winchell's Species. The specimens collected indicate that S. cf. erratica occurs sporadically throughout the Ferron Point and Genshaw formations and has no stratigraphic value. Stropheodonta erratica var. solidicosta Winchell Stropheodonta erratica var. solidicosta Winchell, The Grand Traverse Region, Ann.Arbor, Michigan, Dr. Chase's Steam Printing House, 1866, p..93. (Not available for reference.) Stropheodonta erratica var. solidicosta, Ehlers and Kline, Contr. Mus. Pa1., Univ..of Michigan, v01..14, no. 10, 1934, pp. 153-154, figs. 14-19.. Remarks.--Severa1 Stropheodonta from the Genshaw are placed in this variety after comparison with plastocotypes and with a score of topotypes from the Gravel Point formation at its exposure in the Petoskey Portland Cement Co. quarry on Little Traverse Bay.. The Genshaw forms, which were collected from several outcrOps in different stratigraphic positions, exhibit no greater individual differences than do the Gravel Point forms.p Strgpheodonta erratica var. fissicosta Winchell Remarks.--S. erratica var. fissicosta was collected from three exposures of the Ferron Point formation in the area under consideration. The Ferron Point variety attains a greater size and some Specimens are more finely costellate than the plastocotypes from the Gravel Point formation with which they were compared. This variety was collected only from the Ferron Point formation.p StrOpheodonta sp. aff. S..demissa (Conrad) StrOQhomena demissa Conrad, Jour. Acad. Nat. Sci., Philadel- phia, vol. VIII, 1842, p..258,.p1..l4,fig. 14.. (Unavailable to the writer---cited in Schuchert, C., U. S. Gaol. Surv., Bull. 87, 1897, p.421.) Stronheodonta demissa Hall, Pal..of New York, vol.-4, part I, 1857, ppo. lOl‘lOE, p10. XVII, fiSSO. 2a-28, 2k-280 Remarks.--Nany somewhat crushed and weathered forms of Stro- pheodonta from the Genshaw formation are of the S. demissa type. A specimen of S. demissa from the Jamilton of New York, collected at Smokes Creek, Nindom, N. Y., was available for comparative study.. The Genshaw forms are larger and more gibbous.- Dimensions of an average specimen: length, 32 mm.; width 39 mm.; thickness, 13 mm.. Variations within the Gen— shaw species are confined chiefly to ornamentation and con- vexity of the ventral valve.. Some Specimens are nearly flat in mesial area of ventral valve, with an abrupt lepe on the anterior one-fifth of valve; others are uniformly convex, although the degree of convexity is variable. A form of rare occurrence has 5 or 6 low, very broad rounded costae, each covered with 14 or 15 fine cos- tellae.. These specimens are doubtfully referred to S. sp. aff. S..dem1ssa. Stropheodonta sp..aff..S..demissa occurs from 25 set above the Ferron Point to the bottom of the Killians “3 member of the Genshaw formation. Stropheodonta sp. aff. S. concava Hall 1867 Stropheodonta goncava Hall, Pal..of New York, vol..IV, part I, 1857, pp. 96-96, p10. 16. Remarks.--This species is the largest BrachiOpod$ collected. It is Similar in size to S. concava Hall. Dimensions: length, 48 mm.; width, 52 mm.; thickness, 18 mm.. Ventral umbo swollen; anterior slope long and gentle. Finely multicostellate; other features poorly preserved. Order TELOTHEHATA Beecher Genus CYRTINA Davidson 1858 That portion of Heller's generic diagnosis (Weller, Stuart, 1914, p. 286) upon which the identifications are based is quoted below: "Shells small, semipyramidal in form, with... non-plicated mesial fold and sinus, and simply plicated lateral slopes. Pedicle valve with a high, vertical or arched cardinal area which may be symmetrical or more or less distorted, the delthyrium narrowly triangular, closed with a convex pseudodeltidium which is per- forated at a point below the apex by a sub- circular...foramen.... Internally the dental lamellae are strongly develOped and converge rapidly toward the inner surface of the valve, before meeting which they become joined in a single median septum which continues to the floor and extends anteriorly beyond the center, of the valve. Brachial valve very shallow, with narrow, inconspicuous cardinal area..... Shell substance strongly punctate." Syrtina alpenensis Hall and Clarke Cyrtina umbonata alpenensis, Hall and Clarke, Pal. of New York, vol..8, part II, 1894, p..362, pl. 28, figs. 16-20. Description.--She11 rounded pyramidal to semiglobose, slightly wider than long, with greatest width along hinge line.. Cardinal extremities angular, near 90 degrees. Di- mensions of an average specimen: length, 19 mm.; width, 21 mm.; thickness, 13 mm.. Ventral valve rounded pyramidal with strongly incurved beak; lateral slopes steep, becoming gentler to- ward the cardinal extremities; broad and rounded mesial sulcus with faint obsolete plication on each lepe; sulcus originates at beak and becomes wider and deeper toward anterior margin of valve, extending in front, in some specimens nearly horizontally.. Cardinal area strongly concave, marked by horizontal and very faint vertical stri- ations; delthyrium narrow and triangular, closed by convex pseudo-deltidium perforated in upper one-fourth by elongate, narrow foramen which is often concealed by the incurved beak.. Each lateral lepe has 8 to lO plications with coarsest near sulcus, becoming finer toward lateral mar- gins; at distance of 1 cm. from beak there are from 4 to 7 plications in 5 mm. The ventral interior shows the characteristics of the genus: a strong median septum reaches at least three-quarters the length of the valve; near posterior ex- tremity two dental plates, originating at sides of delthyr- ium, form a sharp V-shaped support for septum; a small knife-like ridge, due to downward extension of the septum, occupies the angle of the V. Dorsal valve semiovate in outline; beak slightly extended posteriorly; posterior hinge line nearly straight. Gently convex with greater convexity in middle of valve where Sharply convex fold raises surface; posteriorly fold is narrow and low, widening and becoming higher toward anterior, median line in some forms marked by a faint groove from posterior to anterior extremities. Valve flat- tened at cardinal extremities; each lateral lepe has 5 to 8 plications which become progressively smaller toward lateral margins.. Internally, the brachial valve contains a bifid cardinal process. Other characters not observed. Surface of both valves marked by concentric growth lines at irregular intervals.. Shell punctate. Remarks.--This species of Cvrtina from the Genshaw has a variable number of plications; Hall and Clarke's figures indicate only 5 plications on each lateral slope, but their written description fails to assign any limits to the number. This form is placed in Q. alpenensis, a dis- tinct species--—not in a variety of g..umbonata. g. glpgp- gpsis is the most abundant species of Cyrtina in the Gen- shaw formation.. This species illustrates well the recurrence of a fauna. It is found in the lower 20 feet of the Genshaw, but is not found from 20 to about 90 feet above the base. It occurs again and in greatest abundance from about 90 feet above the base of the Genshaw up through the lower Killians where it is associated with Mucrospirifer sp. I. Cyrtina sp. I Description.p-Shell rounded semi-pyramidal in outline; much wider than long, with greatest width at hinge line. Cardinal extremities mucronate, acutely angular, Dimen- sions of an average specimen: length, 18 mm.; width, 23% mm.; thickness, 9% mm., Ventral valve with low convexity; moderately incurved beak.. Lateral lepes of umbo steep but flattening toward lateral margin so that extreme one-fourth of valve at each lateral extremity is very gently leping; lepe toward anterior of valve uniformly medium convex.. Mesial sulcus narrow on beak, widening anteriorly; shallow through- out its length, extended in front. Cardinal area moderately concave; delthyrium as described for g. alpenensis. Each lateral lepe covered with 9 to ll plications which are progressively finer from sides of sulcus toward lateral margins. Ventral interior as in Weller's generic descrip- tion. Dorsal valve semi-elliptical in outline; slightly concave, with umbo raised above the semicircular depres- sion surrounding it.. Hinge line straight and wide; beak protrudes slightly.. Crushing has altered the contours of all the brachial valves available for study, but above features seem to be the true ones.. Fold similar to that of g..alpenensis. Seven to 9 plications on each side of fold, becoming finer at lateral margins. Interior not seen. Growth lines form concentric pattern on surface of valves; shell punctate. Remarks.-2This species is readily separable from the other Cyrtinas in the Genshaw by its wide hinge line, sharp car- dinal extremities, its much thinner and lower ventral valve, and the depressed dorsal valve.. This rare species was found only in the trans- itional zone at the top of the Genshaw where it grades into the Killians member.. Cyrtina hamiltonensis I’;all Cyrtina hamiltonensis Hall, Pal.. of New York, vol. 4, part I, 1507, p.. sod, pl.. —44, figs. 25, 29, 40 (not figs. 20- -2(, 30-33, 39, 41-52) and pl. 2{, figs. 3 and 4 (not figs. 1-2). Remarks.e-This species accords with Hall's description, but his description and the accompanying figures indicate a wide variation in characters. Undoubtedly his species is broadly defined, and the Genshaw forms are comparable to the following of his figures: pl. 44, figs. 26, 29, and 40; p1.'27, figs. 3 and 4.. This form occurs sparingly in the transitional zone at the tOp of the Genshaw and base of the Killians._ Note: Several species of this genus identical with the Afton-Onaway forms were collected near Grand Lake in A1- pena and eastern Presque Isle counties. At Long Lake Lodge on the south side of Long Lake g..alpenensis occurs sparingly, and at a stratigraphic position about 15 feet below it Q. hamiltonensis occurs in minor numbers.. Q..Q§Q- iltonensis also is found in small numbers on the east side of Long Lake in the northwest corner of Sec..33 along U. S. Highway 23, T..33 N., R. a E. Both C..hamiltonensis and C. alpenensis occur very abundantly about 0.4 mile southeast of the northwest corner of Sec. 3, T. 32 N., R..o E. along U. S. Highway 23, and g. alpenensis exhibits the same variations as those specimens collected in Cheboygan and Presque Isle counties to the west. Tie fossils from the eastern area are nearly pure white and are beautifully preserved. Genus ATRXPA Dalman lo2o Description.--fhe following observed characters were used in assigning these speCimens to the genus atrypa (Dalman, 162d; hall and Clarke, 1694, pp. 163-175; Weller, Stuart, 1914,.pp..284-265): shell subcircular in outline, dorsi- biconvex, ventral valve nearly flat; greatest width anter- ior to hinge line; ends of hinge line rounded. Surface covered with many radiating costellae crossed by concentric growth lines. Ventral beak incurves over the small car- dinal area and conceals delthyrium and beak of dorsal valve. Interior shows large and widely separated teeth in the ventral valve; conical spiralia were observed to converge toward point of greatest convexity in the dorsal valve. Atrypa sp- Remarks.—-Forms assigned to this genus occur in greater numbers than any other bracniOpod in the Ferron EOint and Genshaw formations.. Because of the very great number of variations, it is not considered feasible to differentiate them in the time allowed for this study. Among the variations noted are differences in ratios of Width to length to thickness; varying convexity of the ventral valve, especially as to the sharpness of the median crest line; slight variations in ornamentation; and wide divergence in sizes. This last feature is of value, however, for the relative numbers of large and small specimens of Atrypa "{— .4 u_ are different at the top and bottom of the formations. The Ferron Point has yielded only small specimens of Atrypa, averaging 13 to 19 mm. wide, with the largest not over 25 mm. in width. The lower Genshaw beds are likewise character- ized by a great number of specimens comparable in size to those in the Ferron Point.» In the GenShaw beds from 1 to 20 feet below the Killians, as in the exposures at Tower Dam, for example, as well as in the Killians itself, large specimens of Atrypa, from 30 mm..to 45 mm. wide, are com- mon.. While the smaller specimens do occur in these latter positions also, they are in greatly reduced numbers. Genus SPIRIFER Sowerby 1615 Subgenus MUCROSPIHlFER Grabau 1931* Mucrospirifer sp. 1 Description.--Subtriangular and conspicuously mucronate in outline; biconvex, with ventral valve exhibiting greater *The subgeneric definition by Grabau is in a Chinese pub- lication (see bibliography) not available to the writer, since the only two known copies in the U. S. are at the Library of Congress and in the Library of the Smithsonian Institute in Washington, D. C. The citation for the sub- genus in Nomenclator Zoologicus does not give the genotype. Schuchert and Dunbar (l941,.p. 213) figure Mucrospirgfer pennatus, originally described by Atwater (1620, ppa 244- 245, p1..1, figs. 2-3). fl. pennatus has the same general characters as those observed on the Genshaw and Ferron Point forms. Scnuchert (1697, p..40l) considers Spirifer mucro- nata Hall (1667, p..216, pl..34, figs..l-32), and g. mucro- natus Hall and Clarke (1694, p. 17, pl..29, fig..6; pl..34, figs..13-22) as synonymous with §..pennatus. Thus, Mucro- spirifer pennatus is considered by the writer to display the characters of the subgenus, at least.. Actually, the termin- ology from which the name is derived would indicate that it is prooably the genotype.. On the basis of these facts, the Genshaw and Ferron Point species are confidently referred to the subgenus Mucrospirifer. convexity.. Cardinal area narrow---2 mm..high-—and tapering toward lateral extremities; hinge line straight, extended, invariably the widest part of Shell. average dimensions: length, 26 mm.;_width, 49 mm.; thickness, 17 mm.. hesial sulcus in ventral valve contains a single low, rounded costa which in a few specimens is quite faint; fold on dorsal valve marked by a single faint mesial groove. Surface of both valves multicostate but no bifurcation occurs; the sharp costae---usually 10 to 16, but more numerous on lar- ger specimens---are crossed by many concentric growth lines. Low beak on ventral valve incurved over very narrow cardinal area. mo median septum in ventral valve; conical spiralia directed toward cardinal extremities. Remarks.--This species from the GenShaw formation closely resembles Spirifer mucronatus (Conrad) as described and illustrated by hall (1661, pp. 216-216, pl..34, figs. 1-23). The more mucronate forms from the Genshaw are very similar to fig. 15 of pl. 34 in hall (idem.); the narrower Genshaw forms resemble closely Hall's figs..9, 11, and 12 of pla 34. The more mucronate forms in the Genshaw are most abundant at the transitional zone at the base of the hil- lians member and up into the lower Killians.. it is common for well-preserved specimens only 20 mm. long to have a hinge line width of over 65 mm.. The highly mucronate forms are usually thinner than the narrower ones. Thus, there are two features of a variable nature in this species of Kucrospirifer: width and thickness. Since both gibbous and thin forms, as well as moderately and extremely mucro- nate forms, all occur in association in nearly every out- crop of similar stratigraphic position, these variabili- ties are not considered of stratigraphic value.. The species itself is useful, however, for a great abundance of this form in association with Chonetes aff. g..fragilis has proved to be a definite indicator of the lower Killians and the transitional zone for a few feet below it. Hucrospirifgr sp. II Remarks.--lhis species is very abundant in the Ferron Point formation; none was collected from the Genshaw.. it differs from £..sp..I above in that it is semicircular in outline and While the hinge extremities are somewhat attenuated, they are not mucronate; the dimensions are grossly different, for the largest specimen of g..sp..Il measures: length, 20 mm.; width, 26 mm.; thickness, 14 mm.. Further, the sharp costae are 10 or ll'in number on each flank» Une probably pathologic form is subtriangular in outline and the mesial sulcus is marked by an off-center coarse costa. no published descriptions consulted apply to this form.. The stratigraphic range of this species is limited to the Ferron Point formation. it is a distinct and stra- tigraphically valuable form. Subgenus DELTHYRIS Dalmah 1626 Delthyris? sp. Remarks.--A very few small specimens are placed in this subgenus although it is not feasible to section one of the specimens to prove the presence of the diagnostic septum. (littel, 1921, p..411.) These Shells from the Genshaw and rerron Point are similar in ornamentation and outline to Spirifer bidorsalis Winchell (Ehlers and Kline, 1934, pp.. 166-169, p1..lv, figs..24-31).. They differ in that they have a straight fold and sulcus, whereas the axis of the fold and sulcus in §. bidorsalis is curved; furthermore, they are somewhat larger than that species.. The Genshaw and Ferron Point forms are also sim- ilar in size, ornamentation, and outline to §..bimesialis hall (Hall and Clarke, 1694, pl..34, figs. 23-26). The few specimens collected come from various stratigraphic positions in the Genshaw and Ferron Point; they are of little value in zoning the formations.t Genus ATanlo McCoy 1644 Athyris sp.- Remarks.r-Members of this genus are not as abundant as most of the other hrachiopoda in the Genshaw and Ferron Point formations in Cheboygan and western Presque isle counties.“ The few specimens collected from each outcrOp are insufficient to show features of stratigraphic value.. The following generic Characteristics, described by Weller (1914, Text, pp..4o4-465), were recognized on the Genshaw and Ferron Point forms: shells transversely suoelliptical in outline; subequally biconvex With full-« length fold on the dorsal valve giv1ng it the Sharper con- vexity; shallow to sharp, deep sulcus on anterior one- third of ventral valve.. ventral beak incurved, concealing foramen.. Surface of both valves covered With broad con- centric lamellae marking each period of growth. FAUEAL zcnss AND CORRELATION pg SECTIONS There are seven faunal zones in the Ferron Point and Genshaw formations in the area investigated. The dis- tribution of the most abundant fossils, including those used in establishing the faunal zones is shown on Fig. 6. The stretigraphic position of the strata in each outcrOp, based on the faunal zones, is shown on the correlation chart, The Ferron Point formation contains a faunal asso- ciation of distinctive species of Chonetes, Pentamerella, and Kucrospirifer. The faunal zones in the Genshaw formation, in ascending order, are: the Chonetes-Pentamerella zone; the lower Pentamerella zone; the Clathrodictyon-Pentamerella zone; Czrtina zone; Mucrospirifer-Chonetes zone; and the Mucrospirifer-Chonetes-Gomphoceras zone. The Ferron Point is relatively easy to identify because it possesses several diagnostic fossils, and is char- acteristically a soft, gray, calcareous shale. The fossils found limited to this formation are Chonetes Sp..aff. coronatus, Kucrcspirifer sp. II, and Pentamerella? cf. pavilionensis.. Other characteristic fossils in the Ferron Point are Aulopora Sp..aff. é. serpens, Pterinea cf. fla- bellum, and several species of Tentaculites.. The last-named forms are not in themselves definitive of the Ferron Point, but are common associates of the diagnostic fossils. .m unsung cumin.“ occaaoouo "pgcqgcuw a o 0 .9m $500.5 ”dammed”; moo Hon 23> modadalqullll .2300:qu 38> dogmas .m a “pas . .mo a Hot com Amway“ on . m mamqocoudfiwn m m: m H A choc . . . .02 9mm. m H .02 squqoon manommm .mo onaBHmamHn _ll ‘0 ' I. ., —— . ___ ———-——- —— ———TOP OF KILLIANS p H>4V—-. :: g4: TENTATIVE CORRELATIONS “ I, - L OF OUTCROP SECTIONS IN THE AFTON- ONAWAY AREA.MIOHIGAN . V “u (I ' PIECE 3-. IL): )6 RIVER 3 ‘1.“- -". , CH. ‘ CY. U.A. CH5 TOP OF GENSHAW- '— lefJ. 9-59 ' ‘52: .v . L. aw. I 0 1,1}: 1 ETTWL 5 +1 j m p;i LEGEND __-_,—_ PL-PENTAMERELLA sp.: on-cnousrss sp. '5 P.1V.- " sew CL.-CLATHRODICTYON 20 : _ - nv.- " 59 v M.S.-"MUCROSPIRIFER" ' nvn- " 52 V: s.r.- SIEBERELLA SR! 25 . . _ 21 k 22 emu-cvmma HAMILTONENSIS cu.-cmn~A sp.: a, §j3;‘,.~,,R,L_ mun-cyan“ UMBONATA ALPENENSIS J-Hv. “fl-OWE" s? u- SIEBERELLA? sp. n 3:3: 51. -= .— ‘ J mv. 3:21:12 U 111: m 2L... “- if: 1 —V‘.Il 4: 50 "TOP OF FERRON POIN , E~~' ___— —-———- ——-‘ L TOP OF ROCKFORT . T 1| 771 -, m ‘ 'm: ,’ . v ‘ I "J h ‘5»: Li}. .L thJ-JUI o r '. I .153 % Thin-bead ed limestone E am“: a 1, 24;: l ‘1 ms :3 itm‘: e 5% G 3.1 I‘m as Shad. :3 EB "331i. six-be 8. :7 e d 113an 2: tan a F 3: (HIRE El, 0 W “A _ '7 _. by Sieberella? sp. I in association with the two forms for which the zone is named. §.? sp. I is found from 50 feet above the base down to the bottom of the Genshaw formation. The Cyrtina zone overlies the Pentamerella- Clathrodictyon beds, and its tOp is about 100 feet above the base of the Genshaw. 'This four and a half foot zone contains at least three Species of Cyrtina in great numbers. The zone is best exposed at Locality 8.. The sub-Killians Genshaw grades upward into the lower part of the black shales and limestones of the K11- lians member. The transitional strata are characterized by an abundance of Kucrospirifer sp. I and Chonetes sp. aff. Q. fragilis, and is referred to as the Mucrospirifer- ghgpgtgg zone. Fish plates of an undetermined genus and pygidia of the trilobite Proetus are also abundant in the transitional zone. The highest strata which can be assigned with cer- tainty to the Genshaw are the black limestones of the Killians member. In the western half of the area the Killians is overlain by the Koehler limestone.. The exact contact has not been observed, but there is no difficulty in distinguish- ing between these two units, for the Koehler is a light gray to buff, fairly pure, lithOgraphic limestone. The Killians is a distinctive black color, and is characterized through- out by Mucrospirifer sp. I and Gomphoceras sp. In the lower part, Chonetes sp. aff. Q. fragilis is abundant. The Killians member is, then, the Mucrospirifer-Chonetes-Gomphoceras zone. The Killians member is rec0gnized at the following localities: 3, (p. 17); 4, (p. 18); 6, (p. 23; d, (p. 27); 10, (p. 32); 14, (p. 38); 15, (p..39); and 15, (p. 39). most of the Killians fossils have a distinctive mode of preser- vation in which their outer surfaces have been penetrated . by black bituminous material which stands in strong relief against the nearly white calcium carbonate preserving the rest of the animal. Particularly does the coral Favositgs show this type of preservation. The uppermost Genshaw in the area is represented by a thin section of limestone exposed two miles north of Afton.. It is referred to the Newton Creek member, but be- cause its stratigraphic position is still in doubt, it is not placed on the correlation chart, Fig. 5. Brief examina- tion of the fossils indicates that the species of Platzra- chella?, PholidostrOphia, Stropheodonta, and StromatOpora? collected from this exposure are unlike those in the Kil-- lians or sub-Killians strata, which are exposed in the vi- cinity at a topographically lower elevation. No single outcrOp reveals all of the faunal zones described, but the section north of Tower (See Fig. 4) shows a maximum of recognized zones. The Milligan Creek exposures show all of the sub-Killians zones but do not include any of that member nor the transitional zones at its base. ENVIRONMENT OF DEPOSITION The sediments forming the Ferron Point and Genshaw formations were deposited under marine conditions in a temp- erate to tropical climate. This is suggested by the charac- ter of the organic remains found in these deposits. Bryozoa, brachiOpods, crinoids, cephaIOpods, pelecypods, and corals are all abundant in these formations.. It is thought that reef corals, which are represented in the Genshaw and Ferron Point by Favosites and stromatoporoid hydro-corals, require temperatures above 68° F. (Twenhofel, 1932, p. 141). This probable truth, together with the fact that warm climates are best suited to the precipitation of calcium carbonate would indicate a warm environment of deposition for the for- mations under consideration.. Near shore or shallow water was the probable im- mediate environment of deposition for these formations. Many overturned colonies of PrismatOphyllum, sometimes two feet in diameter, attest to the strong wave action that prevailed, thus indication shallow water. The thick shells of the very abundant genera, Pentamerella and Sieberella, in the Genshaw are further proof of shallow, marine environ- ment. Reef corals, such as Stromatopora and Favosites, as- as well as the abundant bryozoa in these beds, indicate warm, shallow, marine waters. (Twenhofel, idem., pp. 173- 174). Since shallow water is indicated, it is probable that the region in which the Ferron Point and Genshaw were deposited was located near the northern edge of the Traverse basin of deposition. According to Hake and haebius: "In its major aspects the depression within which the Traverse formation was deposited is an elongated basin, with its principal axis in a northwest-southeast position and situated approximately beneath the inner portion of Saginaw Bay. The maximum observed depth of this basin occurs northwest of the north shore of Saginaw Bay, but it cannot be stated that this is the greatest depth of the basin because there has not been enough drill- ing along the apparent northwest prolongation of the axis to define the area of maximum subsidence." (1938, p» 449).. If this axis is prolonged in the direction suggested by these authors, it would lie about 60 miles southwest of the area of study.. The area studied would then be nearer the deeper parts of the basin than would the type localities for the Ferron Point and Genshaw. This may be an explana— tion for the greater thickness of Genshaw found in Cheboy- gan county than at the type locality in Alpena county to the southeast.. The fact that the Ferron Point is thinner in this more western area as compared with the type local- ity in Alpena county needs another explanation. Erosion immediately after the deposition of the Ferron Point is not probable, for there is no field evidence for a discon- formity; consequently, it may be assumed that upward and downward oscillations of the sea bottom were common in the Traverse basin of deposition.. Newcombe (1933, pp. 75-76) believes that these oscillations are responsible for the alternating shale, calcareous shale, and limestones that compose the Traverse Group. According to Pohl (1930, p. 34) the Traverse seas maintained a northern connection. The connecting seaway "...successively advanced from the northward across the Laurentian mass into an irregularly and intermittently sinking basin occupying southwestern Ontario, northwestern Ohio, all of the Southern Peninsula, and the eastern part of the Northern Peninsula of Michigan, and Open- ing by way of James Bay and Hudson Bay to the Arctic and the North Atlantic Oceans." (Pohl, 1939, p0- 340) Cooper and Warthin (1935. ppo.376-377) indicate by their correlations that a Ludlowville and Skaneateles seaway also extended into southwestern Ontario, New York, Indiana, and southwestern Illinois. Paleogeographic maps prepared by Schuchert (Schuchert and Dunbar, 1941, p. 198) also show these areas as part of the same sea with a sou- thern seaway extending down the Kississippi valley and Joining the Atlantic ocean.. ST. UCTURAL @20ch The area investigated is in the north-central part of the Michigan structural basin., (Newcombe, 1933, P1. III). The regional dip, when calculated from Newcombe's structural contour map (gdgg.), is about 30 feet per mile to the southwest. That the regional dip is very gentle is substantiated by the fact that the greater part of the 1‘, 1 \li‘ - -Z¢Im._..IO:2 -(M—IA‘ \CSSQZCIZCFU.‘ .14.)- IAJOLJZOO quakuonmhum :1 5924a Pump. mm .._<>¢m._.z_ map—.200 .ZOCSszu >mm<30 hmoaxoom mo do... 20 234mm wasp—.200 I \\ III ‘3’ I I s II .s No III . II I I II . I I /I I “ II II . .IIIII I I Q II p teIIwwoh, I I I 5 o I I I I 9-H. I uthofl." I \ ‘ "’I\“ I- Q- 0! "I”?! II \Ilroog no II §\ “ O°o'\\ I I 03 9\ 4k I I \ . I I I s 25.5.3 0: a . A. . I I \f.‘ I I u . ~ II. P \w *nfl \ " WMJ I I“ \‘hNQII ” on S N o 0 \Q I I...\\ \III \ II II . \ ® I I I 36 s _ sss , I e .2, 1...... .- . . . x . l I I \Omdl‘ Jo our." “MG. \\_.I/ / l-\ ‘0” ’ I J a \\ \ I I I I “O \I‘.‘ II‘.‘ I I © \ I I a I s \\OQO I 17.43 5.x... .1... I87: .518... , I, ‘3. . . . . . \ I III . \M \1 a? of. I I I a I . I .‘ . . as. s \ \mur/ . I I i... . . . . 2.. ~If‘ ‘ —' ‘ '--’ ’ ’ \ a a I P I“.J . \ I f “0 II.‘ I I I’OJQ " I OP“. 'IDI so .Pf\ . r A .l. '30 I I \I I “.1 II s w 02. I a h I I I x 4 uh I I \ \~ I I I o I I I I \ t I I I \ %r\ \J as. .~ I I I I'l‘ I II III s s a we... I 2..., , . . I (A I.’ g \% . I II III . I w ‘ ’ I ""‘I . I Q \ . s o I I I § \ - - . I I \ \l . a a "-\ll I I ‘ \ g n o I I a I s *’ a ’ I I I I III \\ \0 II III II I I II \ I I I IIfmu I II 23.122 4qu 23420.22“? .22 «3828 455535 ‘4‘ P. ,4; H uh<4m 1'3 23.593: 32:33 3:60: 3!: Ill:- 0 i n J J 0 I- Q lid.- .l'. 3.33.50. 8.5:: D 0!; Iii!» l Ii; 5.1!; 1"! to"! I! O I- 'Iiliig is; 101;, _ U.‘ .I . .f. ’8‘ Vi I, V ..r r r '''''' U '4 'r II D 3P . Hull‘\ “ ”If A I \..._ IQDh \ | I s\\ _ - ,.,. . I fiat/I * .\ HI I. .- — C. “O. L f . W \t . x . N V . o R , I I :1 “I!!! _n g..- . w I \( — , \‘ 1 ,/ f _ _ . WT, \ I I n— s u a. . 7 .. .. _ III a . . u _ . . 9 . : K. r. _ a . _H. I _ I, ‘ p _ fl _ L T ‘ I 1 x H . .- l i . L . n— W \ . ‘ "J. / ~ \ o / .a o c A u l I \\I\I\ I m _ o o \ n o P I I .. II; I I ' I II III." [:1 V1 Iluul \ K _ n u- , . . ,||+ ‘ _ .- II' on: . n , . . .. s. . a n O. Q. _ on . , . . \i 80»? . _ u. . II 11 I .......... FPJ'I _ - . I . |:\)I . u l _I 7. L “TX .I. .x. k '\\I' _. . II/ . ‘.\\\\ u III/ ox ’AIIIII. .n . 5 1. in II I _u. ~ I 4.“. u. \\\ ! 0‘ a. uni,- _ o. J O. is . . I by \ . . N ..... . 70-5-1111}: \\ .. i ,u l s a at tr ! at . . 1 W, IL 4 y w T x‘ u. f. I I . I . ' II I, n u‘ . o. I ‘ o I . I \\ III! \In ‘ 0 - J", V. .\ ..r m a r. 240.10.: .<>>Pa1eontolO5y, vol. 9, no. 1, pp. 18-29, plo-O, 7o ----------- , (1936) "Devonian StromatOporoids of North America”, part I, Univ. Toronto Stud., Geol- ser., no..39, p..30, pl. VI, figs. 6-9. Pohl, E. R. (1930) "The middle Devonian Traverse 5roup of rocks in Michi5an: A summary of existing knowledge" Proc. U. S..Nat..Museum, vol. 76, art. 14, pp. 1-34. Prosser, S. P., Kindle, 3. M., and Swartz, C. K., (1913) Middle and Upper Devonian, Md. Geol..Survey, Text. Romin5er, C. (1876) Mich. Geol..Survey, vol. 111, part I, "Lower Peninsula", pp. 38-39. Scherzer, M. H..(1900) Mich. Geol..Survey, vol. VII, part I, p. 31. -89- Schuchert, C. (1897) "A synopsis of American fossil brachio- poda, U. S..Geol. Survey, 3u11..87. ------------ , and Cooper, G..A..(193l) "SynOpsis Of the brachiOpod 5enera 0f the suborder Orthoidea and Pentameroidea, with notes on the Telo- tremata., Am..Jour..Sci., vol..22, no. 129, pp. 241-251. ............................. (1932) ”BrachiOpod genera of ' the suborder Orthoidea and Pentameroidea,” Mem..Peabody Mus. Nat. Hist., vol. IV, part I. ------------ , and Dunbar, C..0. (1941) Mucrospirifer pen- natus, Textbook of Ge0105y, part II, Histor- ical Geol., p. 213, pl. 7, fig. 13. Shimer, M..w..and Grabau, A. W. S 902) "Hamilton Group of Thedford, Ontario, Geol..Soc. Am., Bull., V01. 13, pp. 149-186. Smith, R. A. (1914) "The occurrence of oil and gas in Michi- 5an', Mich. Geol. and Biol. Survey, pub. 14, Geol..ser. 11, pp. 215-216. ----------- , (1916) Mich. Geol. and Biol. Survey, pub. 21, Geol..ser. 17, pp. 172-179, 181-185. Stainbrook, M..A. (1938) ”Pentameridae of the Cedar Valley beds of Iowa," Am. Midland Naturalist, vol. 19, no. 3, pp. 723-739. ----------------- (1938a) "Atrypa and Stropheodonta from the Cedar Valley beds of Iowa," Jour. Paleon- t0105y, v01. 12, no..3, pp. 229-256, pl..30-35. Stauffer, c. a..(1909) "The Middle Devonian of Ohio," Ohio Geol..Survey, Fourth ser., Bull. 10. Stewart, G. A. (1927) "Fauna of the Silica shale of Lucas county," Ohio Geol. Survey, Fourth ser., Bull. 32, 1927. Sutton, D. G., and Sutton, A. H. (1937) "Middle Devonian of southern Indiana," Jour. Geol., v01. 45, no. 39 pp. 320‘3310 Twenhofel, h. H. (1932) Treatise on Sedimentation, Second ed. ............... , and Shrock, a. a. (1935) Invertebrate Paleontolo5y. -90- Ver Wiebe, W. A. (1927) "The stratigraphy of Alpena county, Michi5an,” Pap. Mich. Acad. of Sci., Arts, and Letters, vol. VII, pp. 181-192. Marthin, A. S., and C00per, G. A. (1934) "Devonian studies in southwestern Ontario and Michi5an," Ex- plorations and field-work of the Smithsonian Inst., 1934, pp..13-17. -------------- , --- ------------- (1935) "New formation names in the Michigan Devonian," Jour. Hash. Acad. 5010, V01. 25, no. 12, pp. 524-52‘30 ----- , --- ---L--------- (1941) "Traverse rocks of the Thunder Bay region," Unpublished manu- script, pp. 1-37. Weller, Stuart (1914) "Mississippian Brachiopoda," Illinois Geol. Survey, Mon. 1, Text and Plates, 1914. Willard, Bradford, and Cleaves, A. B..(1933) "Hamilton group of eastern Pennsylvania,” Geol. Soc. Am., 3u110, V01. 44, pp..069‘0740 ----------------- , (1939) "The middle and upper Devonian," in The Devonian of Pennsylvania, Pennsylvania Geol. Survey, Fourth ser., Bull. G..l9, pp. 131-200, p1. 15—31. Winchell, A. (1851) Mich'gan Geol. Survey, First Biennial Kept. Progo, pp. 09-710 ............ (1371) Michigan Geol. Survey, Repto-PPO;o. p?- 28-29. ............ (1873) "Michigan, being condensed popular sketches of the topography, climate and geology of the state,” Extracted from Mal- ling's Atlas of Michigan, Claremont Mfg. 00., p. 60. Zittel, M. A., von (1927) Textbook of Paleont0105y, edited by C. A. Eastman, vol. I. o “ROOM USE ONLY n Q I "I7'1111111117111111.1111s