c; 2:... - 3. £1 26... a, my a S. w.“ . Au... a: E a...“ Q O .3 ....,.. g. ; a; i .L a. .. f L Q m“: . , «AU .3.» ac Q .J 4 . c Q R... .. a. . z“ . 3 (a. . woo-0!: «. k .9 AL P. m1 i-V.‘ &. a . (nut. P3334 4. NM...- kN‘ .Idoa «In. 2 fi.\..U . .. «up . a: n5 «.2 «sum 8 .3 A“ a 6 O1 i . 5 H g: .‘k‘i ' ' t. J ' ‘1 CM! C V» :1 E. 3 F x I file 6 . “’1 3...»,8 3. Wu. ..I.« w0 3 as.» .W fiur A m w 3. mm M a.“ 13 .‘w. W‘s“ A h.“ 64.. ¢ «aw Mm... i ..“t-"’ ..k§ I L . -.'- {‘3‘in i 2 . .. . 9... . o l I J o sways “I M- ... {a ”Unfin- Lila a I “a. . (IQ ..4WI I 5* WIN. 0 F...“ in“ . - . 1 n. I a “.55 o u'.‘ a» . m! o L. .1. .3.“ 1,3“ Vx ....~ {9. n ‘3 .m .\Hnno ; w... .n . .v a. V.» "x w. . S H T ..__:2_f5;;g [HESlS This is to certify that. the thesis entitled The Stratigraphic Value of Certain Cryptostomatous Bryozoa of the Traverse Formation, Middle Devon- ian Age of Michfigeasgmed by Arthur E. Slaughter has been accepted towards fulfillment of the requirements for li— degree in m [XXLZQLLzAzL.’Afi2-r4tiiéléfi. Major professor [hue October 12, 1950 -r___ ..._ A.“_ _,__._q,,.,_,__ .- . . THE STRATIGRLPHIG VALUE OF CERTAIN CRYPTOSTOMATOUS BRYDZOA OF TIE TRAVERSE FORMATION, HIDDIE DEVONIAN AGE OF- MICHIGAN by Arthur Edwin Slaughter A THESIS Submitted to the School of Graduate Standiee of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology and Geography 1950 ”’1' fih$l§ 244551 ACIQ‘IOWLEMREWTS Pleasure is had in acknowledging with thanks the guidance and assistance of Dr. WA. Kelly who has given freely of his time, knowledge, and encouragement in the deve10pment of this study. It is likewise a pleasure to acknowledge appreciation to Dr. S.G. Bergquist who has shown a kindly and helpful interest in its progress. To Dr. Bergquist and Mrs. J. E. Smith for editing and improving the text the writer is deeply indebted. Thanks are extended to Mr. F. V. Monaghan and Mr. E. .K. Incas for making photographs of the specimens possible through their valuable assistance and loan of equipment. TABLE OF CONTENTS Acknowledgements . ... . . . . . . List of Illustrations. . . . . . . Intmdnction........... Objectives of the Study. . . . . . Stratigraphy of the Traverse Group Source of Specimens. . . . . . . . Criteria Used in Describing and Classifying Bryozoa. Systematic Descriptions of Bryozoa . . . . . . . . . D18 we Gian O O O O O O O O O O O O O O O O O O O O 0 mmnum O O O O O O O O O O O O 0 O O O O O O O O Biblh mm 0 O O O O O C O O O O O O O O O O O O 0 iii. Page iv 10 26 31 33 LIST OF ILLUSTRATIONS MAPS . Page Map 1 Index Map of Michigan Showing Counties . . . . . . h Map 2 location of Wells Used in This Study . . . . . . . 6 DIAGRAMS Chart 1 Generalized Columnar Section of Michigan . . . . . 7 mm 2 mstnmtion Of Bmzoa. . O O O O O O O 0 O O O C 25 Chart 3 Graphic Representation of the Occurrence oftheBryozoa.................InPocket PLATES ExplanatiOI‘lOfPlatel..............3ll PlateleeeeeeeeeeeeeooeeeeeeeeeeeBS EitplanationofPlateZ..............36 PlateZ..........................37 iv INTRODUCTION Beginning with the Ordovician there are few formations of limestone, especially formations with shale alternations, that do not have a great abundance of fossil bryozoa. The seas of today as well, are rich in the modern orders of this animal. Of the five separate orders of bryozoa only the Trepostomata and Cryptostomata are strictly Paleozoic forms . The Ctenostomata is rarely observed, the Cyclostomata is most abundant in the Mesoaoic, and the Cheilostomata, sometimes regarded as the contin- uation of the Cryptostomata, includes Mesozoic and Recent forms. The trepostomatous forms are found most abundantly in late Ordo- vician sediments and subsequently wane in importance to become extinct in the Permian. The Cryptostomata were at their zenith during the Devonian and fississippian periods and continue to be found in abundance until the Permian. Like the Trepostomata they become extinct at the close of the Paleozoic Era. me culnination of the Paleozoic orders of bryosoa is re- garded as being contemporaneous with the Hmilton stage, (Middle Devonian of New York). lime Michigan counterpart of the Hamilton is the Traverse. The Traverse Formation selected for this starch, like the Hamilton, is a prolific producer of bryuzoan fossils and provides a good source of specimens. The order Cryptosomata is more adaptable to study and identi- fication than the Trepostomata in that most of the foms are identifiable from their external features thus recourse to thin section preparation and study are not strictly necessary. Bryosoa found in Michigan have been used but little in strati- graphic work. Only recently through the endeavor of Boise, mncan, and McNair, have any extensive efforts been made to establish the identification of the fennel types encountered in the State. Previous to the work of these individuals bryosoa were only occa- sionly given enough attention for specific identification; usually noted as addenda at the end of fannal lists. Bassler (1922, p. 376) has stated that, - "The use of fossil bryosoa in stratigraphic work has scarcely attained the importance it deserves. In American Paleozoic strata they are preeminently the fossil to be relied upon in correlation work. They are nearly always abundant and even when poorly preserved exteriorly can be identified by thin sections." In the opinion of the writer Baspler is much too optimistic regarding the importance of eInploying bryosoa in correlation work. The difficulties encountered in identification and collec- tion procedures, mentioned later, are to a considerable degree at variance with his opinion. The foregoing statement is not meant to imply that the bryosoa do not have an stratigraphic usefulness. To the contrary, they do have recognizable stratigraphic signifi— cance and an attempt will be made to point out a new method by which they may be used for correlation work. OBJECTIVES OF THE STUDY The primary importance of fossilized remains of animals 11.. in their use for stratigraphic correlation. This paper has been prepared for the purpose of determining the value of fragments of bryozoan colonies observed in cuttings taken from oil well drilling 3 operations, especially those of the Traverse Formation. The addi- tion of the types identified to the existing faunal lists will add one more bit to the knowledge of the subsurface suppression of the Traverse in southeastern Michigan. Bryozoa found in Michigan have had generally only a very secondary importance and those observed in well cuttings have been more. or less ignored. Bryozoa could take a place of importance in subsurface stratigraphic work comparable to the Ostracoda, if specimens of adequate size and number could be obtained from well cuttings for unqualified identification. This paper will indicate the limitations and serve to verify the usefulness of this fauna in subsurface work. STRATIGRAPHY OF THE TRAVERSE GROUP Portions of the description of the Traverse stratigraphy taken from Oil and Gas Investigations, Preliminary Chart 28 , pre- pared by G. V. Cohee, are reproduced below for descriptive infor- mation regarding the materials connected with this study. "The vaerse group and its correlative rocks are present over a large part of the Michigan basin, includ- ing the Southern Peninsula of Michigan, northern Indiana, northwestern Ohio, southwestern Ontario and eastern Wisconsin. They crop out at the surface in Alpena, Presque Isle, Cheboygan, Brunet and Charlevoix Counties in northern Michigan, near the village of Silica in Incas County, Ohio and at various localities in Kent and Lambton Counties, Ontario, Canada. The rocks of this age crop out beneath glacial drift along the north flank of the Kankakee arch in Indiana and along the Findlay arch in northwestern Ohio and southeastern Michigan. They extend from the Michi- gan basin into the Appalachian basin, across southwestern Ontario in the vicinity of the Chatham sag in Essex, Kent, Lambton, Middleseac and Eigin Counties, where they are called Hamilton formation. MAP I MICHIGAN DEPARTMENT OF CONSERVATION GEOLOGICAL SURVEY DIVISION use: of “(I a II II In O E a” R LAK LAKE suPER’O / \ DOMINION OF CANADA . I g : {I . GOGEBIC l LUCE \ ‘0 "Pg-.\ ALGER \ \ I O 0’9}. mo“ SCHOOLCRAFT CH'PPEM ‘I I II? ‘ ACKINAC «\ - ”of?” I - . l\“ ”MN“ I I ' :TOWW . e e D o f .a .- . ’b I if 0 | o I * ° 0 "” ‘L .0 7 r‘ - v" 0 4» . .I’D‘ I a“: f ./ / msou: ISLE 6‘ I I/Q ’I ' I l / P T I IALPENA ' $9 . /" ° SE00 MONTMORENCY I a I / ‘ 9 .' KALKASKA cruwroao oscom ALCONA | / g. TRAVERSE I I I \ c i , ‘1‘ ISTEE wuroao MISSAUKEEROSCOWON OGENAw IOSCO :0 I l I x/ 9 o I p ,I \ NASON LAKE osczou CLARE GLADWIN z I / Q‘ r I .' I I OCEANA MECOSTA ISABELLA MIDLAND I : NEWAYOO I . I I I ‘\ NONTCALN GRATIOT 5mm“ I “4'. I kl KENT ' '. OTTAWA IONIA CLINTON smssn I V I I .' I \I I I ; . ALLEGAN sum EATON INONAN I I | 0' I I V‘" BUM" KALAMAZOO CALHOUN JACKSON I I .' ST / “WEN CASS BRANCH HILLSDALE LENANEE NONROI: I , JOSEPH I IN 0 I A N A i—--—- o'ITI'O— ' ERIE I ORV I: "The Traverse group in the eastern part of Michigan consists largely of argillaceous limestones and shales with some pure limestone. Westwud the shales become more oalcamous and the limestones purer, and in western Michigan the full thickness of the Traverse group, ex- cept the Bell shale at the base, is largely pure lime- stone with some dolomite and dolomitic and argillaceous limestones. Gypsum is found in the Ferron Point, Genshaw, Newton Creek and Potter Farm formations of the group in parts of northwestem and western Michigan. In south- western Michigan lithographic limestones and some msum are present in the lower part of the Traverse. Chert is abundant in some of the pure limestones and occurs in argillaceous beds. It is particularly abundant in the upper part of the Traverse and also occurs in the lower part in southwestern Michigan. In the Thumb area of south- eastern Hichigan the Traverse is predominantly shale in the lower part with shale and some limestone in the upper part. Eastvmrd into Ontario the Traverse consists of gray lime- stone and shale in the upper part with shale and a few limestone beds in the lower part. In the southern part of the Michigan basin in northern Indiana, the Traverse is light-gray, crystalline limestone. In Wisconsin the Traverse consists of gray limestones, dolomite and shale, with interbedded limestones and shales at the top. ”The Traverse group is thickest in the area of Saginaw Bay, where it has a maxim thickness of approx- imately 875 feet. In parts of Arenac, Ogemaw, Roscommon, Antrim and Otsego Counties the group is more than 800 feet thick. Southward from the areas of greatest thick- ness it thins to less than 100 feet in southwestern Berrien County and in southeastern Lenswee County. Part of this thinning is he to the absence of the Bell shale and the Squaw Bay limestone in Southwestern Michigan. "The structure on the top of the Traverse group con- forms to' structure of the underlying mndee-Rogers City sequence, and shows the dominant northwest-southeast anticlinal folds in the central basin area. ‘The structural alinement in southwestern Michigan is likewise northwest- southeast, but some of the anticlines are alined in northeast-southwest and north-south directions. " 'nie Traverse group has been divided into eleven formations based on material exposed in the northern part of the lower peninsula of Michigan. Although the Traverse is generally diffi- cult to divide in its subsurface lithologic expression, Cohee does assign the pre—Antrim areal geology of Oakland and Washtenaw SOURCES OF SAMPLES EXAMINED FOR BRYOZOA T“ _‘_T_'_| _ __ _, I ; J I I'" 'I—‘[ I l L I - . . I v . J I 1 LLIVINGSTON I OAKLAND ' I °| 5 #3 I L I a I I ""“""“I"'"‘"_"'L" I L l I. I l 02 i g; ;L WASHTENAW I WAYNE '_I._I_.I._-__I__I_-.I WELL N’. I: Pless Nol, SP. No. 15389 WELL No.2: Voornees No.I, SP. No. 3828 SW. I/4, Sec. I3, T.2N., R.5E. SE. I/4, Sec. 32, T23, R? E. Genoa Twp., Livingston County Superior Twp., Washienaw County WELL no.3: Houghi‘on No. I, S. P. NO. II82 S.E. I/4,.Sec.|, T.2N., R76. Milford Twp., Oakland County MAP 2 7 GENERALIZED COLUMNAR SECTION OF MICHIGAN MICHIGAN GEOLOGICAL SURVEY DIVISION I949 SYSTEM. SERIES FORMATION.GROUP LITHOLOGY THICKNESS ECONOMIC PRODUCTS RECENT ‘ _ SAND. GRAVEL,CLAY, boulders, _ SAND. GRAVEL. PEAT. MARL. PLEISTOCENE GLACIAL DRIFT mm 0 I000 FRESH WATER ~PERIAo-CARBONIFERODS" 'RED- BEDS" SHALE,CLAV, SANDY SHALEJypsumi GRAND RIVER SANDSTONE.sandy ml. 80 - 95 BUILDING STONEFRESH WATER PENNSYLVAN'AN SAGINAW SHALE,SANDSTONE,IImesione,coaI 20-535 ngEE-EEQL'FRESH “TER' LIMESTONE. SANDY OR CHERTY BAY PORT UMESTONLSANDSTONE 2-Ioo LIMESTONEFRESH WATER MICHIGAN SHALE.gypsum,anhydniasandsione 0-500 GYPSUM "MICHIGAN STRAV“ SANDSTONE 0-80 GAS ' _ FRESH WATER. BRINE M|$$|$S|PP|AN MARSHALL SANDSTONE.sandy shale I00 400 BUILDING STONE COLDWATER SHALESOIIdsIone.lumesione 500 -||00 SHALE. FRESH WATER SUNBURY SHALE O-l40 BEREA - BEDFORD SANDSTONE, SHALE 0—325 GAS.0IL ELLSWORTH-ANTRIM SHALE. limesione f ICC-950 SHALE,GAS ‘ _ LIMESTONE. 0IL.GAS. TRAVERSE . LIMESTONE, SHALE I00 800 FRESH WATER BELL SHALE. Limcsione 0'80 SHALE ROGERS CITv-DUNDEE LIMESTONE 0-475 L‘MESTONE- (”L-5‘5- DEVON'AN :FJESS'IOVNAETEDROLOMJITE DETROIT RIVER QfiL‘gmLTE-"m°5'°"°-“" ISO-I400 OILGASS'ALT. BRINEf V FRESH WATER SYLVANIA SANDSTONE.SANDY DOLOMITE 0-550 GLASS SAND. FRESH WATEg BOIS BLANC DOLOMITE,CHERTY DOLONITE o-Iooo BASS ISLAND DOLOMITE so - 570 DOLOMITELFRESH WATER SALINA SALT, DOLOMITE, Shaleanhydme 50'4000 SALT. GAS, OIL SILURlAN NIAGARAN Guel II-LocII rI-En adme) _ LIMESTONE. DOLOMITE. {MOMPS'IQMQ' at", 8'5") DOLOMITE, LIMCSTORC,ShOIQ '50 800 O'L. GAS. FRESH WATER Caisraci) CINCINNATIAN Enacmmfid)E ) SHALE,LIMESTONE 250-800 ' . d ORDOVIC'AN .1". ' '" OIL GAS LIMESTONE TRENTON-BLACK RIVER LIMESTONE. DOLOMITE zoo-I000 FRESH Km“ - ST PETER SANDSTONE 0 - I50 I’RESH WATER OZARKIAN PRAIRIE ou CHIEN DOLOMITE.SIuIc o-4Io OR DOLOMITE. SANDY DOLOMITE. - CANADIAN HERNANSVILLE ”Wm I5 500 LANE SUPERIOR ' N T N CAMBRIAN 3:31:31) SANDSTONE 500-2000 935;: 33,8 ‘ (Cwmmma sham-Wm SEMI-PRECIOUS GEN STONES IIILLARNEY GRANITE GRANITE. GNEISS.dioriI¢,ucniI¢ ALGONK|AN NURONIAN SLATES. HEMATITE. SCHIST. IRON ORE. ROOFING SLATE. (I ' I' n ) OUARTZITE. GRANITEJMIDIO. 20000 ROAD METAL. GRAPHITE “I «no u . doiomiic MARBLE ROAD METAL. BUILDING I LAURENTIAN SCHIST. GNEISS. GRANITE STONE,VERDE ANTIQUE. TALC. ARCHEAN GOLD NEEWATIN 3:52;? “unto“ ROAD NETAL OHARTgI counties to the Thunder Bay Limestone and that of Livingston County to the Squaw Bay Fomation. The Squaw Bay is the highest member of the Traverse group and the Thunder Bay immediately pre- cedes it in age. SOURCE OF sesame Three wells were selected at random, one from each of three counties in southeastern Michigan. The cuttings from these wells, the Voorhees #1, drilled by the Ypsilanti Development 00an in Superior Township of Washtenaar County, the Houghton #1, drilled by the Milford Oil and Gas Syndicate in Milford Ton of Oak- land County, and the Pless #1, drilled by the Panhandle Eastern Pipe Line Company in Genoa Township of Livingston County, were examined from the base of the Antrim through the Traverse to the top of the Dmdee Formation. All specimens of brycsoa found in the samples were ranoved for study. From the stratigraphic section of the three wells approximately 700 specimens were ob- tained. The exact location of the wells and their state drilling permit numbers are listed near the bottom of Map 2. METIDIB 0F PREPARATION All of the specimens collected were found free in the well cuttings. In some cases the cuttings, especially the shaly mater- ial, had to be washed with water on a small gauge screen to remove the fine powdery rock that concealed the fossils. In all cases, the specimens were subjected to the deliquescent action of potassium hydroxide tablets to loosen the material encrusting the preservations. Following the potassium mdroxide treatment the fossils were submerged in a bath of either dilute hydrochloric or dilute acetic acid to neutralize the activity of the previous process. A thcmgh washing in water followed the acid bath. Considerable experimenting was done to determine the concen- tration and the length of time required for each treahnent. If the specimens were left too long in the proximity of the potas- sium hydroxide tablets a white residue would accumulate and cover the specimen thus obscuring the structures of the animals. This residue is difficult to remove. If the specimens remained too long in the hydrochloric or acetic acid bath the superficial structures would be destroyed inasnmch as all fossilization was calcareous. Best results were obtained in cleaning the fossils by placing one or two or as many as could be handled without losing their stratigraphic position very close to three or four tablets of the potassium hydroxide on a watch glass. After a period of three or four minutes the fossils were removed and . imersed for not more than thirty seconds in the dilute (hzl) acid and then washed with water. The acetic acid proved slightly more satisfactory than the hydrochloric acid. This method of cleaning was effective in removing the shaly material from around the specimens and thus making the detail of the external features visible. The location and depth of each specimen was recorded on a data sheet and later transferred to Chart 3. Specimens were muted on cardboard slides for detailed simdy and identification. 10 Those less than a millimeter in length were generally disregarded. Photographs were taken on 35 millimeter film with a camera munted on a petrographic microscope. CRITERIA USED DI DESCRIBING AND CIASSIFYDIG 3me1 As previously mentioned, the Bryozoa are divided into five orders and of these only the Cryptostomata and the Trepostomata are definitely lmown from Michigan sediments. Both the stand- stomata and the Cyclostomata are also Paleozoic forms but as yet have not been recognised in Michigan rocks. Although the Trepo- stcmats were collected from the well cuttings, they were dis- carded as soon as their order became apparent, not being pertin- ent to this problan. The similarity in certain families of the orders Tr'epostomata and Gryptostomata presents a preliminary problem of separation that in many cases cannot be accomplished without the aid of thin sections. Ne difficulty is encountered in the bifoliate types, but those specimens. that are cylindrical . in shape show considerable external similarity. Internally the difference of structure is greater. Primary differences lie with the shortness of the primitive portion of the tube of the Crypto- stomata and the abruptness of the passage to the mature region of the tube. This tube indicated by the opening on the surface of the searia, is the living chamber. ' After the manner by which the Cryptostomata was named (Cryptcs: hidden), the true apertures of the manbers of this order are deep-seated within the sooecial tube and ordinarily are ll marked by the occurrence of a hemiseptum. The hemisepta are partial plates projecting into the zooecium. If they project from the posterior wall they are termed superior; from the limited definition of the soarium for no fragment exhibits mre than a very small section of a colon. The possibilities of erecting new species are considerable. In his work with the Cryptostomata McNair (1937) erected twenty- seven new species from the thirty-nine types that he found. Became of the limited number and size of the specimens taken from the well cuttings and the possibility that some types are only variations of the forms described'by other investigators, no new species as such have been erected in this stucb'. Instead, where a fragment or number of fragments cannot definitely be assigned to an existing species a separate and tentative classi- fication has been used. This classification is referred to as species "A", species "B", or species "C" of a particular genera. It is not meant to be the erection of a new species although, with the initiation of further work, these classifications may be borne out and serve as a verification or foundation for new forms. 12 SYSTEMATIC DESCRIPTIONS 0F BRIOZOA Order Cryptostomata "Zoaria compound, often highly complex, differing from Trepostomata in that the primitive part of the tube is usually much shorter and the passage to the mature re- gion more abrupt, i.e., the zooecia have a short tubular primitive portion, above which the mature part is a tubu- lar shaft or vestibule, often with hemisepta, and sur- rounded by vesicular or solid calcareous material; external aperture round; probably Paleozoic representatives of the Cheilostomata. Paleozoic." (Shiner and Shrock, l9h3) Bassler's (1922, pp. 363-361;) informal description of the Cryptostomata is included here for further clarification of the order and for the comparisons that he makes with the other orders of the prwlum. "In this order the zooecia are usually short and have their orifice concealed (mtos, hidden) at the bottom of a tubular shaft or vestibule which is surrounded by a solid or vesicular calcareous deposit. The primitive zocecium is short and quite regular in its outline, being pyriform to oblong, quadrate or hexagonal with the aperture anterior. This same characteristic is shared by the Cheilostomata also and it is probable that the Cryptostomata are nothing more than Paleozoic Cheilostomata. The Cryptostomata differ, how- ever, from the typical members of the Cheilostomata, first in having neither ovicells nor avicularia, second in the mob greater deposit of calcareous material upon the front of the sooecia, third in the frequent development of succes- sive layers of polypides, one directly over the other, thus forming a continuous tube, and fourth, in that whenever a scarium attains an uninterrupted width of more than 8milli- meters it exhibits clusters of cells, differing more or less either in size or elevation from the average sooecia. The last two distinctions are suggestive of the Trepostomata, but the Crypto stomata differ chiefly in that the immature region (primitive cell) is usually much shorter and the pas- sage to the mature region more abrupt, and that hemisepta occur at the bottom of the vestibule. "Some of the Cryptostomata are ramose and have long thin-walled prisimatic tubes in the axial region, with or without diaphragms', precisely as in the ramose Trepostomata and Cyclostomata. They are distinguished from both these 13 orders, however, by the presence of the hemis eptum, the incomplete plate which extends downward and forward from the posterior side of the base of the vestibule into the primitive cell. Sometimes a second hemiseptum is found from the bottom of the cell, in which case the latter is known as the inferior hemiseptum and the former as the superior one. The purpose of the hemisepta is unknown, although it is possible that they served as sup- ports for a movable operculum. "The relationship of the Cryptostomata to the Cheilo- stomata is further suggested in the zoarial forms they assume and in the beauty of the surface of the zooecia. In the typical Cryptostomata the zoarium consists of two thin layers of sooecia growing back to back into erect sword- shaped, ramose, ribbonlike or fan-shaped expansion. In other Cryptostomata the mafia form lacelike empansions consisting of only s. single layer of cells with the reverse side covered by a dense layer of striated or minutely granulose tissue. In the remaining sections of the order the zoaria are ramose with the zooecia arising from a real or imaginary axis and opening on all sides of the cylindri- cal stems. Usually the soaria are contimous, but .in some of the bifoliate and ramse forms they are divided into segnerrts, articulating with each other. "Most of the Cryptostomata can be identified from the sooecial surface characters, but in some of them, particu- larly the bifoliate and solid ramose species, thin sections of them are as necessary as in the Trepostomata. On account of their geometrical regularity of zooecial form, thin sections.of the Gryptostomata are often most beautiful objects under the microscope. "The order commences in Early Ordovician times, reaches its greatest development in the Devonian and Mississippian, and becomes extinct at the close of the Permian.” Genus EUSPIIDPORA Ulrich 1890 "Zoaria consisting of small, flattened, irregularly divided branches. Zooecial apertures subcircular or elliptical, arranged in four or more rows over the central portion of the branches between slightly elevated longi- tudinal ridges, bearing numerous, small nodes. At brief intervals, occurring alternately on each side of the branch, there are several short rows of apertures directed obliquely upward and outward from the central rows, 11; extending nearly to the sharp margins. Between these lateral rows the margin of the frond is more or less indented, but a wide depressed non-poriferous space remains. This is covered with exceedingly fine granu- lose striae. Thin sections show that between the ends of the zooecia there is a vertical series of shallow lenticu- lar vesicles, separated from each other by a thick layer of tissue. All the remaining interspaces are traversed vertically by exceedingly mmerous mirmte tubuli." (Ulrich, 1390, page 389) mspilopora species "A" (plate 2 figure 7) Zoarium ramose. Branches straight and flat. Edges serrate or smooth. Margin nonporiferous and narrow. Apertures ellipti- cal or subcircular in outline; separated longimdinally by dis- tances less than length of the apertures and separated trans- versely by distances approximately equal to the width of the apertures; arranged in regular longitudinal series. Zooecial tubes flattened for a short distance, then abruptly bent outward. Ridges are low and straight. Specimens approximate the characters designated to Euspilopora serrate Ulrich but differ in the longitudinal spacing of the apertures. Occurrence: Upper zone - Oakland County. Genus ACAN‘I‘HOCLIMA Hall 1886 "Zoarinm ramose, solid. Cells arising from a fili- form axis ; apertures arranged in longitudinal rows separated by ridges. Usually with one or two nodes longitudinally betwaen the cells, which are represented in the interior by short tubuli." (Hall, 1887, p. xv) Acanthoclema species "A" Zoarinm composed of cylindrical branches. Apertures opening 15 directly outward, elliptical in outline; separated longitudinally and transversely by a distance less than the length of the aper- ‘ ture; situated in longitudinal ranges, with apertures in adjacent ranges altenating. Ridges between ranges sinuous and bear a single row of minute rounded nodes. Ho hemiseptum observed. This variant is strikingly similiar to Trematopora (Orthopgra) tortalinea, Hall, externally but has the filiform axis that characterizes the genus Acanthoclema. It differs from g. ohioense, HcNair, in its distinctly sinuous ridges. Occurrence: Upper and lower zone - Washtenaw County; upper zone - Oakland county. Loanthoclema Species "B" (plate 2, figure 3) Zoarium composed of cylindrical branches. Apertures opening directly outward, elliptical outline; longitudinal separation less than the length of the apertures; transverse separation less than the width of the apertures. Peristomes low and inconspicuous. Ridges are sinuous and prominent. Two conspicuous nodes -and sometimes a third inconspicuous node occur in the interapertural space in a linear series. Nodes connected to short tubules. Species "B" is similiar to Trematopora bigpinulata, Hall, but has the filiform axis characteristic of the gems Acanthopora. ‘ Occurrence; lower zone - Livingston County. icanthoclema species "9" (plate 2, figure 1) Zoarium composed of cylindrical branches. Apertures opening directly outward, elliptical in outline; separated longitudinally 16 by distances less than the. length of the aperture; separated transversely by distances less than the width of the apertures. Apertures in adjacent ranges alternate in position. ' Simmus ridges between ranges. Peristomes are inconspicuous. Apertural interspace is distinctive as one large pit. No nodes observed. Occurrence: lower zone - Livingston and Washtenaw counties. Lcanthoclema hamiltonense Hall (plate 2, figures h 8:: S) . Zoarium solid cylindrical branches . Apertures oblique to surface and slightly curved; arranged in longitudinal series; longitudinal separation less than the length of the apertures; transverse separation less than the width of the apertures. Apertures in adjacent ranges alternate in position. Ridges between ranges are sinuous and prominent. Peristomes are inconspicuous. Apermral interspace marked by two elliptical to quadrangular pits, one above the other. These pits are somewhat more ellip- tical than those diagrammed by Hall of his specimens. Occasionally a mall node connected to a short tubule between the apertures. Occurrence: lower zone - Livingston and Washtenaw counties. Genus STREBIDTRIPA Ulrich 1890 'Zoaria ramose, solid. Zooecia radiating from an imaginary axis, their primitive portion long, mbular; or from a linear axis when they are somewhat shorter. Inferior hemisepta best developed, situated rather for down. Apertures regularly elliptical, or somewhat truncated at the posterior margin, surrounded by a slight peristom l7 and, within this, sometimes a narrow sloping area; arranged usually in rather regular longitudinal series. Just back of the aperture, occupying the depressed front of the cell, there are from one to twelve or more small pits which, when numerous, are arranged in two or three rows. Very small acanth0pores occasionally present." (Ulrich, 1890, page 1:03) Streblotrypa anomala McNair Zoarium cylindrical branches. Apertures open directly outward and are elliptical in outline; separated longitudinally by distance from one half to approximately entire length of aperture and trans- versely by distance less than width of aperture. Apertures are situated in a linear series and are separated by low sinuous or straight ridges. The apertures in the adjacent ranges alternate in position. Peristomes low, some of which cannot be distinguished from the ridges. Small acanthopores present on most peristomes at ends of the apertures. One of'five mesopores exist between most apertures. Zooecial walls thin in axial. region but thickened at periphery. Occurrence: Upper and lower zones - Washtenaw County; lower zone - Livingston County. Streblotypa species "A" (plate 2, figure 6) Zoarinn composed of cylindrical branches. Apertures open directly outward; elliptical in outline; longitudinal separation variable, usually less than the length of the apertures; transverse separation less than the width of the apertures. Apertures in a linear series separated by sgraight or sinuous ridges. Adjacent series of apertures alternate in position. Peristomes low, dif- ficult to distinguish from the ridges. 18 One or two acanthopores present. One to four mesopores in longitudinal. series at the ends of the apertures. Zooecial walls thin at the axial region thickening at the periphery. Hemisepta rarely observed. Streblotqpa species "A" does not have as strong ridges as does S. anomala but are such more pronounced than those of Streblotrypa species "B“. Occurrence: lower zone - Washtenaw County. Streblotrypa Species "B" (plate 1, figure 8) Zoarium composed of cylindrical branches. Apertures are elliptical in outline; separated longitudinally by a distance from one half to approximately the entira length of the aperture and transversely by distance less than the width of the apertures; situated in linear series both longitudinally and obliquely; separated by faint sinuous ridges. Peristomes inconsPicuous. Single pit at the base of each aperture. Hemisepta not observed. Ridges are not as pronounced as those of Streblotrypa species "A". Occurrence: Upper and lower zones - Washtenaw, Livingston, and Oakland counties. Gems INTRAPORA Hall 1883 "Bryozoum growing as in Stictopora; stipe and branches broad, bifurcating at somewhat regular intervals. Both sides celluliferous, the intercellular spaces regularly punctured or pitted as if by numerous mimte cell-apertures, l9 entligefntercellular space vesiculose." (Hall, 1883, Po 7 Intrapora irregularis Stewart (plate l,'figure 7) . Zoarium consists of an irregular eXpanion. Apertures circular to subcircular in outline; arranged in an irregular linear series; ordinarily separated by one or more sub-angular mesopores. Peristomes low and sharp. Mesopores of variable size abundant, sub-angular or polygonal in outline, small, in some places grouped in clusters; commonly appear to ring the apertures, common in space between four sooecia. No acanthopores observed. Occurrence: Upper and lowar zones - Washtenaw, Livingston, and Oakland counties. Germs ACIDGENIA "Segnented, arising from cylindrical rootlets, two seguents from truncated ends of preceding one, each obconical and striated base, later becoming flattened and bearing apertures in linear series, separated by ridges, largest in marginal row; lunaria prominent.“ (Shiner and Shrock, 19th, page 270) Genus SULOORETEPORA (D'Orbisnv 1810) Definition from Ulrich, 1890. - "Zoaria ramose, bi- foliate, the branches acutely elliptical in cross section, with sub-parallel, sharp, non-porifemus, striated, granu- lose, or smooth margins. Zooecia apertures generally arranged in longitudinal series between ridges, sometimes in more pronounced oblique rows. Apertures sub-elliptical, partially closed in the fully matured condition with a more or less developed lunarium, that is always situated upon the side nearest to the margin of a branch. Inter- spaces finely striated, granulose, or smooth, and never withegits or cells, excepting when worn. " (Ulrich, 1890, P0 3 20 Sulcoretepora altenata McNair Zoarium flat with alternately arranged branches. llargin ' nonporiferous. Edges round. Subcircular to elliptical aper- tures that open directly outward; those closest to the margin more rounded than those in the central portion. Apertures separ- ated longitudinally by a distance less than the length of the openings and separated transversely by a distance less than the width of the apertures. lunaria .strong. Ridges are straight, prominent, and rounded. This speciés has narrower and more prominent ridges, sharper peristomes, and more closely spaced and smaller branches than Sulooretepora §_i_e_i_§_§_i_... A The latter qualification is undeterminable in fragnental specimens. Occurrence : lower zone - Washtenaw County. Sulcoretepora deissi McNair (plate 1, 'figure 2) Zoarium thick with alternately arranged branches. Margin nonporiferous with moderate width. Edges round. ipertures open directly outmrd; subcircular to elliptical with those closest to the margin more circular than those in the central portion. Apertures separated longitudinally by distances less than the length of the apertures and separated transversely by distances less than the widths of the openings. Peristomes are sharp and thin. Lunaria strong and thin. Ridges straight and not conspic- uous on older portions of the colony. This species is readily distinguished from the other species of Sulcoretepora by its greater relative thickness, weak ridges, 21 and abrupt rounded edges. Occurrence: Upper zones - Washtenaw and Oakland counties; lower zone - Livingston County. Sulcoretepora incisurata (Hall) (plate 1, figure 1;) Zoarium consists of flat, dichotomizing branches. Margin nonporiferous and narrow. ' Edges are sharply angular. Apertures vary from nearly circular to elliptical in.outline; those in the marginal. rows larger than the others. longitudinal and transverse separation of the apertures is variable. Peristomes are strong, equally or unequally elevated. lunaria conspicuous. Ridges are prominent and broad. Occurrence: Upper and lower zones - Washth and Oakland counties; lower zone only - Livingston Caimty. Sulcoretepora Mica McNair (plate 1, figure 5) Zoariun flat with dichotomizing branches. Margin nonpori- felons, rounded and narrow. Apertures open directly outward; circular to elliptical in outline; those near the margin larger and mre circular than those in the central portion. Apertures separated transversely by distances less than the widths of the openings and longitudinally by distances greater than the length of the apertures. Peristomes narrow and prominent. The lunaria project upward from the peristomes conspicuously. Ridges prominent and rounded. Occurrence: Upper zone - Washtenaw County; lower zone only - Livingston and Oakland Counties.‘ Sulcoretepora Mince McNair variant "A" (plate 1, figure 1) 22 Zoarinm flat with dichotomizing branches. Margin non— poriferous, rounded and narrow. Apertures open directly outward; circular to elliptical in outline; those near the margin larger and more circular than those in the central portion. Apertures separated longitudinally by distances less than the length of the apertures; separated transversely by distances less than the widths of the openings. Peristomes narrow and prominent. The lunaria project upward from the peristomes very conspicuously. Ridges prominent and rounded. This variant differs from Sulcoretepora Mica only in the spacing of the apertures. All other characters are identical. Occurrence: lower zone - Washtenaw County. Sulcoretepora M McNair Zoarimn flat with bimrcating branches. Margin nonporiferous; width moderate; outer edge straight. Elliptical apertures open directly outIrard; those closest to the margin more rounded than those in the central portion. Apertures separated longitudinally by a distance greater than the length of the apertures; transverse separation less than the width of the apertures. Peristomes are broad and prominent. mnaria absent. Ridges straight and prominent. . V Occurrence: Upper and lower zones - Washtenaw County; lower zone only - Oakland County. Sulcoretepora species "A" (plate 1, figure 3) Zoarium flat and of slightly greater than average thickness. Margin nonporiferous. Edges round. Apertures elliptical; those 23 closest to margin more circular than those in the central portion. Apertures separated longitudinally by a distance greater than the length of the openings; separated transversely by distances equal to the width of the openings. lunaria rare, indicated by a weak fold when present. Peristomes are not present. Ridges absent. Lack of peristomes and the spacing of the apertures differ- entiates this species from Sulcoretepora species "B" Occurrence: Upper zone - 1:B'ashtenasr County; lower zone - Livingston and Washtenaw counties. Sulcoretepora species "B" (plate 1, figure 6) Zoarium flat and of average thickness. Edges blunt and keeled. Apertures very close to edge leaving a 37331 narrow margin. Apertures elliptical; those nearest the margin more rounded than those in the central portion. Apertures separated longitudinally by irregular distances; separated transversely by distances less than the width of the opening. Innaria are common and prominent. Peristomes conspicuous. Ridges are broad and rounded; straight or sinuous. This species is easily distinguished from Sulcoretepora species "A" by the conspicuous peristomes and spacing of apertures. Occurrence: Upper zone - Oakland County. Mooretepora sulcata (Winchell) Zoariun consists of narrow, dichotomizing branches. Apertures Open directly outward; elliptical in outline; those nearest the margin more circular than those in the central part of the branch. Apertures separated longitudinally by distances greater than the 2h length of the openings and transversely by distances less than the width of the apertures. Peristomes sharp and elevated on the side closest to the margin. Innaria numerous. Ridges between ranges of apertures low, narrow, and inconspicuous. Margin non- poriferous, narrow, and with sharply angular edges. Some of the apertures very close to the edge of the branch. Occurrence: Upper and lower zones - Washtenaw and Livingston counties; upper zone only - Oakland County. Chart 2 DISTRIBUTION OF BRIOZOA Key r - rare c - common a - abundant Acanthoclema hamiltonense Acanthoclema species "A" icanthoclema species "B" Acanthoclema species "C" Acrogenia Euspilopora species "A" Fenestrate types Intrapora irregularis Streblotrypa anomala Streblotrypa.species "A" Streblotrypa.species "B" Sulcoretepora alternate Sulcoretepora deissi Sulcoretepora incisurata Sulcoretepora lyrifica Sulcoretepora lyrifica var. "A" Sulcoretepora oblique Sulcoretepora Species "A" Sulcoretepora species "B" Sulcoretepora sulcata 25 Livingston Co. Upper Zone Washtenan Co. Upper Zone Oakland 00. Upper Zone Livingston Co. Lower Zone 6 00) 00 $1 on $8 0:3 :1 rd 3:; 53 533 B: as T353 5': 0 c c 1' 1‘ l‘ 1‘ 1' a a O 1‘ 1‘ 1‘ 1‘ 1‘ 1‘ c 26 DISCUSSION Although no effort has been made for a precise tabulation, it is believed that as many as to percent of the specimens col- lected were unsuitable for use. Size, concealment by host rock, and poor preservation of the features were the prohibiting fac- tors . Of the remaining specimens, approximately 140 percent were of the order Trepostomata, not pertinent to this thesis. When- ever possible, the remaining 300 odd specimens were identified to species. If not identified to species than the generic name was indicated; the fenestrate types excepted. Each cryptostoma- tons bryozoan identified is recorded on Chart 3 which appears at the end of the paper. On Chart 3 the fossil specimens are keyed by number‘and logged according to the depth from the top or height above the bottom of the Traverse Formation at which it was found. In addition the host rock type also is recorded. The chart clearly pictures the occurrence of two separate zones in which the bryozoa are found. These zones have in each case a stratigraphic separation apprordmating 50 feet. The lower zone occurs in the bottom to to 60 feet of the formation and the higher zone is also upward of 60 feet in thickness. Chart 2 is a composite record of the occurrence of the var- ious types of fossils. This chart indicates only one significant difference apparent between the two faunal zones. The commence of Acanthoolema hamiltonense and Acanthoclema species "C" in the lower group distinguishes that zone from the higher zone. This observation, however, may not have significance after further 27 investigations of the formation are made. .Additional collec- tion of specimens may show the occurrence of these two types in the higher, younger fennel group. Chart 2 shows a freq- uency rating of the individual types although the validity of such frequency is significant only to the extent of this part- icular study. Future work using more specimens may or may not verify the rating. is can be observed in Chart 3 the bulk of the specimens were taken from the shaly limestones. A large portion of the stratigraphic section from Oakland County is shale and few fos- sils were found in it. The specimens collected from this shale , are friable and easily destroyed in washing and cleaning pro- cesses. In some places the hard limestones seemed to yield the best specimens in that they were broken out of the host rock cleanly by the drilling process. None were found in the cherty or dolomitic zones. Drilling methods made a noticeable difference in the size of the specimens available for collection. Cuttings from the wells drilled by the churn type method produced specimens that are larger and thus easier to work with than the cuttings from rotary type drilling operation. Size of the specimens recovered are an important consideration in the identification process. Zoarial fragments a millimeter or less in length do not exhibit enough of the structures of the colory or sufficient zooecia for purposes of satisfactory identification. The unilaminate zoarial forms of the Cryptostomata such as 28 Fenestrellina and Polmra generally exhibit a fenestral struc- ture. The lace-like construction of these types is very fragile. Though they may occur in abundance in southeastern Michigan the difficulty of recovery may prohibit their use to any significant degree. Because of their delicate construction they are easily ground up by the action of the drillers' bit. So few of this type of fossil were found and so poor was the preservation in the three wells investigated that no effort was made. to estab- lish their identity. Their occurrence has been listed in Chart 3 only as fenestrate types. Problems encountered in the identification process were many and varied. Some of these are mentioned .in the following six paragraphs for they bear directly on the evaluation of the usefulness of the fossils that could be taken from well cuttings and used in stratigraphic correlation. Because of the pronounced morphological changes that have been observed in some types, for example, Sulcoretepora gig-{gs}, McNair, in the transition from younger branches to more mature regions of the colony, it is possible to mistake the identity of the fragnents taken from the well cuttings . McNair (1937, p. 158) is quoted as follows: "Young branches of Sulcoret ra 9239.14. are relatively narrow, with definite longitu dges and prominent peristomes, usually without lunaria; the margins of the branches are angular in cross section. Older branches are wider; the margins are more rounded than those of young ones, the ridges lower and broader, and the peristomes less sharp, lunaria being strongly developed on the marginal ranges of the zooecia. Very old branches are wide and are ' two to three times as thick as the young branches. Most 29 of the very old branches have lost the longimdinal ridges which are replaced by irregular striae. Marv peristomes are much inflated and project above the surfaces of the branches . Lunaria are strongly developed. Many of the normal peristomes and some of the enlarged ones are covered by secondary sclerenchyma." In the well cuttings the fragments of the colonies obtained are very small and contain but few sooecia. With such variation in the structure from the mature to younger portions of the so- arium as 11ch has stated the true relationship may not be estab- lished. Hall (1887, p. 2142) made mention of this problem and regarding Sulcoretepora incisurata states : "The variations of this species are so great that where only the extremes are observed, they would naturally be re- garded as belonging to different species." Such mistaken identity may lead to the erection of either relatively few or many new species. The soarinl fragnents are partimlarly adaptable to this and, as pointed out below, such establishment of new species would not be detrimental to strati- graphic correlation work if confined to the use of well cuttings. Another difficulty involved in working with the well cuttings is the limited number of specimens that are available. If but one specimen of a particular type, especially the cylindricany shaped ones, is found, then the process of identification is limited to one of two procedures. Either the specimen must be defined from the superficial structure alone or from the internal construction by means of a thin section. If the thin section is made then the external features are destroyed and no further re- course may be made to them. Furthermore, unless the thin section 30 is ground to a precise position, a meticulous and delicate process that often fails, it is valueless. The possibility of making a mold and cast of a fragment to preserve the external structures is remote because of the extremely small size of the fragments and of the minute detail of the individual sooecia. It is rare to find a specimen that is more than tree or four millimeters in length and in order to Split satisfactorily a specimen into two parts saving one half and making a thin section of the other, a minimum length of five millimeters is necessary. Some of the distinguishing characteristices of certain species are based on the angle at which the branches diverge from the main stems or by the presence of large primary and small secondary branches. Neither of these features can be detemined from the small fragnents. The above mentioned classification problems are discouraging and all serve to lessen the value of the fossil fragments for stratigraphic purposes. However, if a umber of new species whether artificial or not, are established as result of the pecu- liarities of portions of the soaria, they may be used in cor- relation work. The stratigraphic range of these new species will vary no more than the range of true species. Contrarily, con- sideration should be made of the possibility of the fragnents of two or more distinct species resembling each other and yet not having the same stratigraphic range . No attempt has been made at this time to correlate the fauna described here with an definite stage or stages of the Traverse. ‘ However, it is noteworthy that the fossils identified 31 compare favorably with the fauna described by McNair collected from the lower half of the Traverse, that is, below the Thunder Bay Stage- and enclnding the Bell’Shale, in the northern part of the lower Peninsula‘and with those of the Silica Shale in Incas County, Ohio . The presence of Acanthp clema hamiltonense and Sulcoretepgra incisurata, both described by Hall from the Hamlton of New York, bears out the Traverse correlation with subdivisions of that eastern fomation. (INCLUSIONS It can be shown as result of this study that ‘the Traverse of southeastern Michigan may be divided into four distinct parts. Chart 3 reveals an upper unfossiliferous acne, an upper fossil- iferous zone, an intermediate barren zone, and a lower fossil- iferous zone. These divisions can be shown without making aw specific identification of the fossils found. Such zonal rela- tionships may be as valuable in subsurface stratigraphic cor- relation as the listing of the particular faunal types. It should be noted that the lower fossiliferous zone closely par- allele the Ostracoda some in the Traverse found by 6mm, (1950 , p. M) . There are shown here two species only that distinguish one fossiliferous some from the other. It is possible that addition- al collecting will show more forms that are not comon to both zones. Additional collection, however, also may reveal that all forms are common to both cones. 32 Certain limitations in the recovery of specimens of suit- able sise and number must be considered. Similiarly, problems in the identification procedures serve to lessen the reliability of some types of the bryozoa. There are, however, some individ- uals on which unqualified identification may be made. From these distinguishable foms stratigraphic relationships can be deter-f mined. It is the opinion of the writer that although there are readily distinguishable fonns available for identification from the framents that the difficulty and labor involved in making these identifications is not worthy of the effort. It is prob- able that the knowledge of the zonal occurrence of this fauna will be as valuable as knowledge of amr specific types. 33 BIBLIOGRAPHY Bassler, R. S. (1922), ThplBgyosoa, or Moss Animal, Smithsonian Report for 1920, pp. 339-380. Campau, D. E. (1950), The Stratigraphic Distribution of Ostracoda Within the Traverseiformation fifths Michigan Basin, Unpubl. Masters Thesis, p.12. Cohee, G. v. (192m, lithology and Thickness of the Traverse Group in the Michi an Basin U.S.G.S. Oil and Gas Investigations Preliminary Chart . Deiss, c. F. (1932), A Description and Stratigraphic Correlation of the Fenestellidae from the Devonian of Michi an Contrib. fins. 51., Univ. Mich” Vol. III, No. 13, pp.233-275. Duncan, Helen (1939), Trepostomatous Bryosoa from the Traverse group of Michigan, Contrib. Mus. Pal. , “’I'iniv. Mich., Vol v, NO. 10, ppe 171-2700 Hall, James, and Simpson, G. B. (1887), Corals and aligns: Con- taining Descriptions and Figures of pecies from e wer HelderbergI @per Helderberg and Hamilton Group_s, Paleontology of New ork, Vol. V, 29 pp., pls. 1-66. McNair, a. H. (1937),. glyptostomatous Bryozoa from the Middle Devonian Traverse Grou of Michi an Wntrib. Mus. Pal. , Univ. Mich., Vol. V, No. 9, pp. 103-170, 11; pls. Nickles, J. 11., and Bassler, R. S. (1900), A Synopsis of American Fossil Brvozoa including Bibliography and Synergy, U.S. Geol. ., 11. 175, pp. 9-663. . Shiner, H. w., and Shrock, R. R. (19141;), Index Fossils of North America, John Wiley and Sons, Inc., New York, pp. 2177-275. Stewart, Grace, A. (1927), Fauna of the Silica Shale of Lucas County, Geol. Surv. Ohio, F'ourth Ser. Bull. 32, pp. 257-276. Ulrich, E. 0. (1890), Paleozoic Bryozpa, Geol. Surv. Illinois, Geglog and Paleontolog, Vol. VIII,‘ Part II, Sec. VI, pp. 28 -688. Figure 1 Figure 2 I Figure 3 Figure h Figure 5 Figure 6 Figure 7 Figure 8 EXPLANATION OF PLATE 1 Sulcoretepora lyrifica variant Sulcoretepora deissi . . . . Sulcoretepora species "A". . Sulcoretepora incisurata . . Sulcoretepora lyrifica . . . Sulcoretepora species "B". . Intrapora irregularis. . . . Streblotrypa species "B" . . 3h "All Page . 21 Figure I Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 PLATE l 35 Figure 1 Figure 2 Figure 3 Figure I; Figure 5 Figure 6 Figure 7 EXPLANATION OF PLATE Acanthoclema species "C" . . . Acanthoclema species "C" . . . Acanthoclema Species "B" . . . Acanthoclema hamiltonense. . . Acanthoclema hamiltonense. . . Streblotrypa Species "A" . . . EuSpilopora Species "A". . . . Figure I Figure 2 Figure 3 Flgure 4 Figure 5 Figure 6 Figure 7 PLATE 2 3? ‘ —‘——A _ at, u. I, ll a. , I . ~ .- k "7 LPN“ t 1'1" :91.- “filthy-m - . _—._——- —-o-—- .—~— -. -._..._fi.—.——a aw. fRESENTATIo P LIVINGST S. P. I (— "..__L_AJ_Q.A AM 77 “III! 3 :IGRAPHIC SE l l