: Gorell University Library Ithaca, New York MA.Geol. Survey re 3 19 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN BALTIMORE THE JOHNS HOPKINS PRESS 1919 M, The Bord Baltimore Preas BALTIMORE, MD., U.S A. vy Te ’ “ ge x ; COMMISSION EMERSON C. HARRINGTON, i : 5; : PRESIDENT. GOVERNOR OF MARYLAND. HUGH A.McMULLEN, . . . . . . . . COMPTROLLER OF MARYLAND. FRANK J. GOODNOW, ‘i ‘ is ‘ EXECUTIVE OFFICER. PRESIDENT OF THE JOHNS HOPKINS UNIVERSITY. A. F. WOODS, . ‘ : ; ; : 2 : SECRETARY. PRESIDENT OF THE STATE COLLEGE OF AGRICULTURE, SCIENTIFIC STAFF Epwarp BenNnEeTT MATHEWs, STATE GEOLOGIST. SUPERINTENDENT OF THE SURVEY Epwarp W. Berry, CuHaRLEs K. Swartz, J. T. SINGEWALD, JR., EvcEene H. Sapp, Miss Myra ALF, ASSISTANT STATE GEOLOGIST. GEOLOGIST. i : GEOLOGIST. ‘ j 3 ASSISTANT. 5 ; : SECRETARY. LETTER OF TRANSMITTAL To His Excellency Emerson C. Harrineron, Governor of Maryland and President of the Geological Survey Com- mission, Sir:—I have the honor to present herewith the seventh of a series of reports dealing with the systematic geology and paleontology of Maryland. The preceding reports of this series have dealt with the Devonian, Lower Cretaceous, Upper Cretaceous, Eocene, Miocene, and Plio-Pleistocene deposits and the remains of animal and plant life which they contain. The present volume treats of the Cambrian and Ordovician deposits and their contained life. These rocks comprise the oldest fossiliferous rocks of the state, a knowledge of which is extremely important from a scientific, educational, and economic standpoint. I am, Very respectfully, Epwarp BENNETT MATHEWS, State Geologist. JoHNS HoPpKINS UNIVERSITY, BaLTiIMorE, September, 1919. CONTENTS PREEACH diica cones the chapel oie par eeaite geese Ae Ae ae eR MER S 19 THE CAMBRIAN AND ORDOVICIAN DEPOSITS OF MARYLAND. By Rte Ss BASSEER sited aialare Avail ae Saveiare, ai aac otek ayaicne duo sare wate SES 21 INTRODUCTION: snaie d-sado' Rus Utusan dole sa ets seen aw et See ea Se 23 TEE PEVGIOURAUVIEY ya 65/6 40k 6404S 4 CORES Ged OEMS dob e BE ee ES Kae Oe 23 MEE GEOLOGY. 5: speech obeyed! Si. stay b's, 6 RI ne Beans teak tne ha Ge pale 24 FISTORICAL REVIEW asp ssiey a auig catia duwsea awnes eed eee ease yes be te 25 BIBLIOGRAPHY * i26e cite yc Rye asa acs OG Rha aaa Gina a A GE RN ES 34 PALEOGEOGRAPHY OF THE CAMBRIAN AND ORDOVICIAN... 0.0.0... 000 eeeee 45 STRATIGRAPHIC AND PALEONTOLOGIC CHARACTERISTICS. ......00 0000 00ee ee 50 CAMBRIAN SILICEOUS FORMATIONS...... 0.00 c eee cece eect eens 52 The Loudon Formations os sc6 004-06 a.06 eee ea 40 645% ose ew eS 53 The Weverton Sandstone...... 2.0.0. cece ccc eee eeee 54 ENE GT DCTS. SRC gi.5 wince aise Beso hia wb ag NSE Hew a Renew bow Rs Be 57 The Antietam: SGndstoness:.052 0345846 sou ee swe es see eee es 58 CAMBRIAN-ORDOVICIAN LIMESTONES .......-0 0220s eee cece eee reese 60 The Tomstown Limestone...... 6... eee eee eee 61 Topography’ Vavige caw sa npeh be a eee an wed 61 Lithologic Characters .......... 0.0.0.2 ee eee eee eee 62 Residual Products «2... ccc ccs cece see ccctaeee scans 63 Economic Features .......... 00.00 ce eee eee eee eee 64 Areal, DistTibutiod: sciccsacqasvccoheoed sau ees ess 65 THICKNESS 4: 4ec2e ste ouaddes ogeiceas Sees ase 66 Age and Correlation .3. 3.662.265 45 sev sees vans yess 66 The Waynesboro Formation....... 0. ccc cece eens 66 Name and Synonymy .......... eee eee eee ence 67 Lithologic Character and Thickness................ 68 Topographic Form. 3... .....s.n6esedeses ewes gesea ee 69 Tomstown—Waynesboro Boundary ................ 69 Areal Distribution: ius .ccaus cece eid edad oha mes oe aie 70 Economic Features . eS, ie ) ( Ne ° ee 1s ON t} Lh 92 THE CAMBRIAN AND ORDOVICIAN Deposits oF MaryLAND products left in the soil by the weathering of the limestone. The top, middle and lower portions are especially well characterized by siliceous products, such as chert, flint and sandy shale fragments, which are dis- cussed in detail in succeeding paragraphs. Lirnotocic CHaracter.—Although the Beekmantown limestone differs considerably in its lithological development in the eastern and western parts of the valley, the formation as a whole is composed of much purer limestones than the underlying Conococheague. On the other hand its purest beds are inferior in calcium carbonate content to the high average of the overlying Stones River limestone. The purer limestones of the Beekmantown are interbedded with greater thickness of relatively impure finely laminated beds which occur, or at least outcrops, so fre- quently that the presence of these laminated limestones is a good criterion for the formation. This characteristic minute lamination of the average rock of the formation is due to impurities in the rock and most apparent on weathered surfaces. Pink and white fine grained marbles in ledges of considerable thickness also are of common occurrence in the Beekman- town, especially in the lower half of the formation. Marbles occur in the underlying Conococheague limestone, but as they are always associated with the characteristic siliceous banded limestone of that formation they are readily distinguished from the marble beds of the Beekmantown. But it should not be forgotten that siliceous banded limestones quite similar to those of the underlying Conococheague beds occur also in the lower Sfth of the Beekmantown. These are so constantly developed in the eastern half of the valley that the part containing them has been mapped as a distinct basal division under the name of the Stonehenge limestone member. This basal member can be recognized locally also in the western part of the valley, but here its lithologic characters are hardly distinct enough to warrant its separation in the mapping. As practically all of the Beekmantown areas of Maryland are covered by gently rolling cultivated farm lands it is almost impossible to make out the complete section of the formation in any particular place. How- ever, by assembling incomplete sections in various parts of the valley the MaryLANpD GEOLOGICAL SURVEY 93 following generalized section for Maryland and southern Pennsylvania has been described by Ulrich in his Revision of the Paleozoic Systems :’ Generalized Section of Beekmantown Limestone in Southern Pennsylvania and Maryland Feet Base of Stones River limestone with quartz pebble conglomerate and CAMLIMO WER CHERE. c5.i5:5 nao preey Ontes B8 whwid w eiecece Sinenie ea E> eoemLE Hard dense white chert and granular quartzose chert forming by secondary silicification, cauliflower chert.................0006- 40 Fine grained gray, finely laminated, interbedded-pure and magnesian unfossiliferous limestone with sandy chert and limestone and dolomite conglomerates at the top............ 0c see eee cece cence 400 Turritoma zone. Thin bedded argillaceous and massive purer limestone containing the Turritoma fauna. Many of the beds weather so as to appear riddled with worm borings...............ce eee eeee 200 Alternating beds of pure dove, pure gray and magnesian gray unfos- siliferous limestone often laminated, with occasional beds of fine limestone conglomerate ........ 0... cece cece cece eee ee ne neces 300 Massive pure dove gray and magnesian limestone terminated above by sandy fossiliferous chert containing Syntrophia lateralis, Maclurites sordida and species of Liospird......... ccc cee eae 75 Ceratopea zone. Blue and dove fossiliferous limestone cherty in the upper half, containing Ceratopea and associated fossils. At the base is a blue limestone filled with rounded quartz grains............ .. 250 Cryptozoon steeli zone. Fine grained nearly pure limestone with some magnesian beds and several layers of porous chert............. 275 Dove, pink and bluish fine grained pure limestone and marble....... 300 Odlitic, cherty blue and gray limestone holding the Cryptozoon steeli fauna and weathering into platy yellow chert................. 60 Stonehenge limestone member. Massive dark blue to gray limestone with contorted argillaceous and siliceous laminations weathering to sandy shale, interbedded with edgewise beds and o@lites......... 250 Massive blue to gray pure limestone weathering white, with cepha- lopods and gastropods occurring in reef structures............. 250 Top of Conococheague limestone with sandy laminae and beds of edgewise CONZIOMETALTE 4 cas icee estas Waterways Mee ted Fé Wekes ROS RA Res - 2400 From the stratigraphic standpoint the important divisions of the above section are the Stonehenge member and the three zones marked respec- tively the Cryptozoon steelt, Ceratopea, and Turritoma zones. The faunal and other characteristics of these zones are discussed in succeeding paragraphs. 1 Bull. Geol. Soc. America, vol. xxii, No. 3, 1911, pp. 652-655. 94 Tur CAMBRIAN AND ORDOVICIAN Deposits oF MaryLAND While the general section given above holds fairly well for all parts of the Valley, the detailed stratigraphy of the formation in the eastern and western parts is, as mentioned above, somewhat different. The best exposure of the Beekmantown limestone east of the Martinsburg shale belt is adjoining the Chambersburg-Gettysburg Pike one mile east of Chambersburg, Pennsylvania. This section, measured by Ulrich and Stose, is ‘given below with slight emendations to show the position of the fossil zones. Section of Beekmantown Limestone One Mile East of Chambersburg, Pennsylvania Feet Base of Stones River, containing fine limestone conglomerate and laminar and OGlitic chert: . 4.60 ccsnwassuads seeds ters awed eewaw ea ded sa eoes ates Interbedded fine-grained pure and magnesian limestones, finely laminated in part and containing small quartz geodes; porous sandy chert near top; dark-blue layers near base containing numerous gastropods (Turritoma fauna) and ostracods and mottled by magnesian material that weathers out, leaving pits and holes...............0e ce eeeeees 600 Alternating pure dovecolored and gray limestone and magnesian lime- - stone, with layer of sandy chert..........-. cece cee eee eee e cence eee 375 Bluish to dove-colored fine-grained fossiliferous limestone, at the base containing rounded quartz grains. Ceratopea fauna at top.......... 100 Pink fine-grained marble, containing layers of milky quartz chert; gastropods of the genera Ophileta, Maclurites and Eccyliopterus rather abundant ........... reigayd belies inetoanreicts Aitalalee Settler etace acai d athe Sane 275 Pure dove-colored and blue fine-grained limestone, with some pink lime- stones; contains fragments of trilobites............ 0. cece ee eee ee eee 285 Fine-grained dove-colored to dark gray. limestone with fine conglomerate and odlite beds; abundant chert in upper portion, in part odlitic and conglomeratic. Cryptozoon steeli in middle part.................. 145 Stonehenge limestone member: ; Fine-grained light to dark gray limestone containing wavy laminae of sandy matter that stand in relief or fall to sandy shale on weathering and thick beds of “‘ edgewise ’” conglomerate; gastro- pods in upper and fine fragments of trilobites in lower portion.. 225 Dark to very light gray massive limestone, containing Dalmanella, Ophileta and trilobite fragments............. IN dp aac tah ida aupeassire 260 Top of Conococheague, containing wavy and sandy laminae and beds of coarse limestone conglomerate..............4. ieeeAphhatger ea aers sis eee 2265 West of the shale belt, the details of the Beekmantown section are somewhat different, although the several fossil zones can be readily MARYLAND GEOLOGICAL SURVEY 95 recognized. No continuous well-exposed section of these strata was noted in Maryland, and the section repeated below is one, published by Ulrich and Stose, of the northern continuation of the formation in southern Pennsylvania. This section is broken and probably incomplete 480 feet beneath the base of the overlying Stones River limestone. If the Turri- toma zone which was not observed is present in this basin, it may have been faulted out or is concealed by covering soil and debris. However, it has been recognized in the southern continuation of the belt in Maryland. Section of Beekmantown Limestone near Mouth of Licking Creek, Franklin County, Pennsylvania Interbedded pure and magnesian limestone of Stones River type......... she Light-gray, finely laminated magnesian limestone and white dolomite with cherts of rosette type at the top......... cee cece ee eee eee eee 340 Dark and light coarse dolomite. ....... ccc ccc cece eee ett eee eens 140 Rocks folded and largely covered; white dolomite, dark-blue odlitic lime- stone, and dark coarse dolomite with yellow blocky sandstone frag- ments and rosette cherts; exact continuity indeterminable, but the previous beds are apparently repeated by folding................00% Interbedded pure and magnesian limestone, with beds of coarse dark dolomite, and in the lower part beds of “‘edgewise’”’ conglomerate; at base contains Ceratopea gastropods, cephalopods, and trilobites...... 350 In large part finely banded magnesian limestone with few pure lime- stones; contains fine conglomerate beds and gastropods...... aoheaviuind 170 Largely dolomite, some coarse and dark; large scoriaceous black chert and coarse sandstone at the base. ......... ccc eee cee eee eee ee eens 130 Chiefly dolomite, coarse and dark in upper part, with some pure fos- siliferous limestone; bed of granular limestone with numerous Ophileta and pinkish fine-grained limestone near middle; cross- bedded banded limestone at base, locally unconformable on under- VY iT WOUS: ae. ole et cas tcd adele aud ands Side dpegi oven’ oes 8a. dates aoe. aie te a aera chav iadn sian etegeee 290 Fine-grained limestone seamed with calcite and dolomite beds with flinty chert containing Cryptozoon steeli at the base........... cece eee eee 65 Partly covered; lower part pure dark limestone with a few beds of finely laminated magnesian limestone and fine white odlite near base; small rough chert with casts of crystals at the base............. cece e eee 130 Light-blue limestone with fine contorted sandy laminae that weather in relief; contains fine dark conglomerate with red limestone pebbles and fragments of trilobites .......... ccc cece eee eee ete ee te tenes 165 Purer fine even-grained limestone with few sandy partings.............. 530 Sandy laminated limestone, much contorted (Conococheague)........... 4 Chambersburg-Mercersburg folio U. S. Geological Survey. 7 96 THE CAMBRIAN AND ORDOVICIAN Deposits oF MaryLAND Comparison of these sections brings out several salient differences in the lithology of the two areas. East of the shale belt, the Stonehenge member with its characteristic siliceous banded limestone, is distinct enough to be mapped as a separate unit, but west of that belt the siliceous banding of the lower Beekmantown is not so well developed. However, the same faunas are present in these strata in both areas so that there is no doubt as to the presence of beds corresponding to the Stonehenge member in both. The higher beds in each area also contain similar faunas, but the lithology is somewhat different, limestone predominating in the east and dolomite in the west. Chert in large quantities weathers from certain portions of the dolomite in the western area, but it is not so conspicuously developed in the east. The two sections illustrate the lithologic changes occurring in the formation going from the east, where over three-fourths of the formation consists of pure limestone, across the strike to the western side of the Valley where more than half of the strata is more or less highly magnesian. In Appalachian areas still further west, as in central Pennsylvania, the change to magnesian limestone becomes yet more pronounced. Fauna Zones.—Although the lithologic features of the various por- tions of the Beekmantown limestone vary considerably, the basal member is the only division which can be definitely recognized from the character of its strata. Above this lower division—the Stonehenge member—three distinct faunal zones aid in the recognition of their respective horizons. These are in ascending order above the Stonehenge member, the Crypto- zoon steelt zone, the Ceratopea zone and the Turritoma zone. The value of these zones is not local for they have a wide distribution. Stonehenge Member.—The village of Stonehenge, just east of Cham- bersburg, Pennsylvania, is located on the lower beds of the Beekmantown, which are sufficiently distinct lithologically and faunally from the remain- ing strata of the formation to warrant their separation as a distinct member. This Stonehenge member is composed of massive finely con- glomeratic pure limestone in the lower half and siliceous banded limestone alternating with layers of large edgewise conglomerate in the upper half. MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XIII 1G. I.—EXPOSURE OF STEEPLY INCLINED STONEHENGE LIMESTONE (UPPER DIVISION ) AT CHARLTON, MARYLAND, SHOWING THE DISINTEGRATION INTO SILICEOUS SHALE, UPON PRO- LONGED WEATHERING. iG, 2.—TYPICAL EXPOSURE OF EDGEWISE CONGLOMERATE FROM THE UPPER PART OF THE STONEHENGE LIMESTONE, BALTIMORE AND OHIO RAILROAD, ONE MILE NORTH OF BALLS, MARY- LAND. MaRrYLAND GEOLOGICAL SURVEY ov The lower Stonehenge limestone is made up in large part of very massive blue to dove-colored limestone weathering bluish-white or white. The outcrops are always of a distinctly lighter color than the associated formations. This feature is one of several that serve unmis- takenly in identifying this basal zone of the formation. On close inspec- tion a large part of these massive limestone ledges appears to the un- assisted eye as granular in texture, but under a lens the granules prove to be very small brecciated pieces of limestone usually less than a sixteenth of an inch in diameter. These small fragments are of a more distinctly white color than the surrounding matrix and the combination of a light blue rock crowded with lighter colored minute angular fragments is very distinctive. The lower division is further distinguished by absence of chert. In all of the numerous outcrops that have been studied no chert of any kind has been observed either in the weathered limestone or in the soil derived from it. At intervals varying from an inch to two inches the limestone develops very thin layers of carbonaceous or argillaceous material which gives it a banded aspect. These layers or laminae are usually about one-eighth of an inch in thickness, flat and parallel with the bedding planes. They are quite unlike the sandy intertwining laminae so characteristic of the upper division of the Stonehenge member. Along the National Highway just south of Funkstown there are splendid outcrops of typical lower Stonehenge limestone where fossils may be found and its lithologic character can be studied to advantage. Hagerstown and vicinity also affords numerous, excellent and instructive exposures of those beds. Excepting the shells of a few brachiopods the fossils in this zone cannot be cleanly extracted from the rock because they are so firmly cemented to the fine-grained matrix that in breaking the limestone with a hammer the fracture passes through the fossils and not along their surfaces. It is only upon the weathered surfaces of the ledges that the fossils can be discerned, and at that merely as cross-sections. The exposures near Funkstown have shown clearly that the fossils of the lower Stonehenge fauna, especially the cephalopods and gastropods which constitute much 98 THE CAMBRIAN AND ORDOVICIAN Deposits oF MARYLAND the greater part, occur mainly in reef-like masses. These reefs are of slightly different material than the enclosing rock, lenticular in form, and seldom exceed two feet in maximum thickness. Straight and coiled cephalopods are the most abundant fossils seen in cross-sections of these reefs, but Maclurites and Ophileta-like gastropods are not uncommon. Most of the beds of the upper Stonehenge resemble the Conococheague limestone so closely in their development of sandy laminated strata with numerous beds of edgewise conglomerate that in areas of faulted or intricately folded strata the distinction between the two formations is made with difficulty. The absence of chert in the weathered Stonehenge limestone contrasting with its frequent occurrence in the Conococheague is perhaps the best of the physical means of separation. It will be observed also that in the upper Stonehenge the sandy laminae are more undulating and interwoven than in the laminated beds of the Conoco- cheague in which commonly they form relatively parallel bands. The presence of shells of cephalopods and gastropods in the Stonehenge also serves to distinguish this member from the Conococheague which has never yielded any molluscan fossils. In areas where the sequence is normal the boundary between the two formations is readily determinable by the criteria given. Desirable and conclusive corroboration may be secured by establishing the lower Beekmantown sequence of (1) the lower Stonehenge composed of pure dove-colored to gray strata containing beds of a minute limestone conglomerate; (2) dark impure limestone with undulating siliceous laminae followed by (3) relatively pure limestone consisting largely of pinkish marbles. All the hills within the city of Hagerstown and its vicinity are formed of the upper Stonehenge limestone, and as the quarries for building stone in the early days were located on these hills, it follows that many of the older buildings in Hagerstown are of this limestone. The stone is not only easily quarried and dressed, but as it whitens in weathering and the edgewise conglomerate and wavy laminae become distinctly visible, it has also a handsome and unique appearance. Several of the churches are constructed of Stonehenge limestone and its value and beauty as building rock may be seen particularly in St. John’s Episcopal Church on West Antietam Street, and the Presbyterian Church at the corner of Wash- MaryLanp GEOLOGICAL SURVEY 99 ington and Prospect streets. The conglomeratic nature of the rock is especially well brought out in the many stone embankments about Hagerstown in which long exposure to the weather has emphasized this and the laminated character. At the present time brick and concrete construction have largely displaced this limestone as building material. Although the upper division of the upper Stonehenge is well exposed at many localities in Maryland, perhaps the best places to study it in detail "are in the various railroad cuts around Hagerstown. The cut on the Western Maryland Railway one-half mile west of Bissel éxposes the characteristic edgewise conglomerate and the heavy, wavy laminde espe- cially well. At this place, as well as at other localities around Hagers- town, a few granular layers are found crowded with brachiopods and poorly preserved gastropods. Seventeen species of fossils have been noted in the Stonehenge lime- stone of Maryland and Pennsylvania. Following Ulrich* these have been correlated with the Tribes Hill limestone fauna of New York. The same fauna is found also in the upper part of the Kittatinny limestone in New Jersey and in the basal or Stonehenge limestone division of the Canadian in central Pennsylvania. The brachipod Dalmanella wemplei Cleland is found in abundance in certain granular layers, but other fossils are not so common. The cephalopods are almost confined to reef-like structures in the purer limestones of the lower half. The gastropod Ophileta com- planata Vanuxem is found in both the lower and upper parts of the member and it may be considered the characteristic fossil. Representatives of one species of fucoid and 16 species of invertebrates, including one brachiopod, six gastropods, five cephalopods, three trilo- bites, and one branchiopod crustacean, have been found in the Stonehenge member in Maryland sufficiently well preserved for specific identification. Fragments of a few more species too imperfect for accurate determination have also been noted. The gastropod Ophileta complanata is highly characteristic of this part of the Beekmantown and the fauna may be known as the Ophileta complanata fauna. The Stonehenge limestone 1Ulrich, Revision Paleozoic Systems. Bull. Geol..Soc. America, vol. xxii, 1911, No. 3, pl. xxvii; Ulrich and Cushing, Age and Relations of the Little Falls dolomite—N. Y. State Museum, Bulletin 140, 1910, p. 137. ‘100 THe CAMBRIAN AND OrpovicIAN Deposits or MARYLAND does not leave any residual chert upon weathering and its contained fossils unfortunately do not become silicified. As a result, their preserva- tion is-not of the best and natural sections in the rock or poor casts are ‘the rule. The granular beds associated with the edgewise conglomerate of the upper part of the Stonehenge limestone is the most favorable place for collecting the brachiopod and gastropod shells, some of these beds being fairly crowded with specimens of Dalmanella wemplei. The cephalopods and trilobites have in the main been found in reef-like structures in the lower Stonehenge and their occurrence is therefore quite sporadic. At one point a stratum will exhibit numerous cross-sections of fossils, but a foot or two away where the reef material composed of a very fine edgewise conglomerate has disappeared, no trace of a fossil can be found. ‘The following table gives a list of the Stonehenge fauna and shows the distribution of the species in the Kittatinny limestone (upper part called the Coplay limestone) of New Jersey and the Tribes Hill limestone of New York, formations with which on stratigraphic and paleontologic grounds, the Stonehenge is correlated. LIST OF STONEHENGE LIMESTONE FOSSILS SHOWING DISTRIBUTION Kittationy _ Stonehenge Pleads | aris ea Pea. PERE ees of Beekman- Beene New Jersey New York] town Maryland Palewophycus tubulare Hall.............. ee * * Dalmanella wemplei Cleland............. :% * * Ophileta complanata Vanuxem........... x * Ophileta levata Vanuxem . * * Eccyliomphalus multiseptarius Cleland... * * Pleurotomaria ?? floridensis Cleland ..... * * Raphistoma ? obtusum Cleland .......... bg * * Raphistoma ? columbianum Weller....... * es * Orthoceras primigenium Hall............ * * * ‘Ooccras kirbyi Whitfield..............5-- i * * * Cyrtoceras gracile Cleland............... * * ive * Cyrtoceras beekmanense Whitfield........ oes #8 * * Cyclostomiceras cassinense? (Whitfield).. 2 ey * * Asaphellus gyracanthus Raymond........ * * * Hemigyraspis collieana Raymond......... 2 a * Symphysurus converus (Cleland)......... * * * Ribeiria nuculitiformis Cleland........... but * * CAMBRIAN AND ORDOVICIAN, PLATE XIV MARYLAND GEOLOGICAL SURVEY 1G. I.—VIEW OF A WEATHERED OUTCROP OF THE UPPER STONEHENGE LIMESTONE, EASTERN EDGE OF HAGERSTOWN, MARYLAND. Fic. 2—V1EW TAKEN FROM HILL OF UPPER STONEHENGE LIMESTONE, EASTERN EDGE OF HAGERSTOWN, MARYLAND, LOOKING EAST, SHOWING EFFECT OF WEATHERING OF THE VARIOUS FORMATIONS UPON TOPOGRAPHY. THE VALLEY IN THE FOREGROUND IS IN THE LOWER STONEHENGE PURE LIMESTONE WHILE THE RIDGE IS FORMED OF THE SILICEOUS, MORE RESISTANT UPPER STONEHENGE. SOUTH MOUNTAIN IS SEEN IN THE DISTANCE, MarYLAND GEOLOGICAL SURVEY 101 In Maryland and southern Pennsylvania, the Beekmantown strata fol- lowing the Stonehenge member are so uniform in lithologic character that their separation into distinct formations is impracticable. In the Nittanny and other valleys in central Pennsylvania the corresponding strata not only attain a much greater thickness, but also are so developed that four formations are readily distinguishable. These are, in ascending order, (1) the Stonehenge limestone at the base with a thickness of 662 feet; (2) the Nittanny dolomite, 1267 feet thick, cherty and holding the Cryptozoon steeli fauna in its lower part; (3) the Axeman limestone 158 feet, and (4) the Bellefonte dolomite 2145 feet thick. The entire series, with both overlying and underlying formations, is to be seen in excellent and practically continuous exposures at Bellefonte, Pennsyl- vania. As this section gives the maximum known development of the Canadian system in the Appalachians, the four formations into which it has been divided as above by Ulrich have been adopted in the general time scale. Cryptozoon steelti Zone.—Following the Stonehenge member, which has just been described, are 600 or more feet of cherty odlitic limestones, dove- colored, fine-grained pure limestone and usually dense textured pink marble. The basal 60 feet consisting mainly of odlitic cherty limestone contains the characteristic fossil of this division—a globular mass, com- monly four to eight inches in diameter composed of concentric layers and supposed to represent the secretion of calcareous algae to which the name Cryptozoon steeli has been applied. Though doubtless calcareous originally, these rounded masses are now almost without exception more or less completely replaced by silica in the form of chert. This fossil occupies a similar position in the Beekmantown throughout the Appa- lachian Valley and it is so abundant and characteristic that this division is termed the Cryptozoon steeli zone. Subaerial decomposition of these particular strata leaves a light reddish residual clay and soil containing an abundance of ordinary yellow platy chert besides the numerous rounded silicified masses of Cryptozoon. These cherty residual masses unfailingly identify the outcrop of this zone. It is particularly well exposed in the 102 True CamMBRIAN AND ORDOVICIAN Deposits or MaryLanD railroad cut about three-fourths of a mile east of Charlton, Md. Here deep weathering and decomposition of the steeply dipping limestone strata has removed their calcareous matter and left only residual clays with the chert clearly marking its position. The abundance of chert and silicified Cryptozoon heads formed in the weathering of this zone is well attested by the frequent piles of chert collected along the roadways. Immediately following this cherty zone with Cryptozoon are 300 feet of dove and pink fine-grained pure limestone, of which a considerable portion can be called marble. These marble beds are well shown in several railroad cuts around Hagerstown. Fossils are rare in these strata, but an occasional layer shows traces of species found also in the underlying beds holding Cryptozoon steeli. This zone ends with 275 feet of fine-grained, nearly pure limestone with occasional beds of magnesian limestone and several layers of porous chert. The platy chert, weathering out of the limestone of the Cryptozoon steeli zone is common at all outcrops of the zone, but is so abundant in the western half of the valley that it occasions a distinct row of hills marking the line of outcrop. This topographic feature and the numerous masses of Cryptozoon associated with the chert cause this portion of the Beekman- town to be easily recognized. The following species have been found either associated with Cryptozoon steelt or in strata underlying it, but still included in this division : Fossils of Cryptozoon steeli Zone Cryptozoon steeli Seely Rhabdaria fragilis (Billings) Tetradium simplex new species Syntrophia lateralis (Whitfield) Maclurites affinis (Billings) Eccyliopterus triangulus (Whitfield) Ophileta compacta Salter Hystricurus conicus (Billings) At the very base of this zone two interesting fossils have been found associated with the usual gastropods. These are the sponge-like organism Rhabdaria fragilis Billings and Tetradwum simplex, a new species of coral of particular interest in being the oldest known undoubted coral. MaryYLAND GEOLOGICAL SURVEY 103 The Maryland outcrops of the Cryptozoon steeli zone are so numerous and easily located both on the map and in the field that only a few locali- ties need be mentioned. In the western half of the valley, outcrops along the Western Maryland Railway, especially three-quarters of a mile east of Charlton, show these rocks and their contained fossils. East of the Martinsburg shale belt, exposures in the vicinity of Williamsport and also north and west of Hagerstown have afforded fossils. In the western part of the valley the line of hills in the Beekmantown area next to the Beekmantown-Conococheague boundary represents this zone, but in the eastern part the exposures parallel a line of hills caused by the more resistant Stonehenge beds. Ceratopea Zone.—Succeeding the dove and pink pure limestones and marbles of the Cryptozoon steeli zone are 250 feet of blue and dove lime- stone cherty in the upper half, containing horn-like fossils known by the generic name Ceratopea. The exact nature of these fossils is unknown, but they are believed to be the opercula of large gastropods like Maclu- rites. From a stratigraphic standpoint they are of considerable interest because this particular species and the fauna associated with it has a wide geographic distribution, but restricted geologic range throughout the Appalachian and Mississippi valleys. Free silicified specimens of this organism occur in the soil where this zone outcrops, or they may be found attached to the limestone. Associated with the Ceratopea are a few species of gastropods and fragments of trilobites, but the Ceratopea itself is the most characteristic fossil of the division. In Maryland numerous outcrops of this zone can be found in the vicinity of Halfway, particularly in cuts along the Cumberland Valley Railroad. Localities near Hagers- town have also afforded this fossil, although in no place has it been found in the abundance that prevails in Virginia and the states to the south. The fauna of the Ceratopea zone so far identified consists of nine species. Fragments of a few other species have been noted, but they are too imperfect for description and can only be identified with certainty when a monographic study of the entire Beekmantown formation has been made. 104 THe CAMBRIAN AND OrpDOVICIAN Deposits or MARYLAND Fossils of the Ceratopea Zone Dalmaneila electra (Billings) Pleurotomaria ?? canadensis Billings . Hormotoma artemesia (Billings) Maclurites sordidus (Hall) Ceratopea keithi Ulrich Raphistomina laurentina (Billings) Goniurus caudatus (Billings) Pliomerops salteri (Billings) Isochilina gregaria (Whitfield) Turritoma Zone—The next division of the Beckmantown consists of * about 575 feet of pure dove and gray laminated magnesian limestone, which contains in its upper part high-spired gastropods with a species of Turritoma apparently confined to these beds. The lower 375 feet of the Turritoma zone is composed of alternating highly magnesian, finely laminated gray limestones and pure gray and pure dove limestone with occasional beds or streaks of fine limestone conglomerate. The basal 75 feet of this portion occasionally exhibits a few fossils of which Syntrophia lateralis and species of Maclurites and Liospira are most often found. The association of species called the Turritoma fauna is found only in the upper 200 feet of this division where the fossils usually occur in beds that weather so as to appear riddled with worm borings. Here the fossils are not silicified, but they occur as dolomitic casts, often, however, in good preservation. They are extremely fragile and much care is required * to preserve them. Gastropods, particularly the species Turritoma acrea (Billings), are most conspicuous. A number of species of fossils, too imperfectly preserved for recognition, occur in this zone in Maryland; eight species have been identified specifically. The strata with Turritoma are the uppermost fossiliferous rocks of the Beekmantown, but they are followed by 400 feet of finely laminated, gray, interbedded pure and magnesian limestone of the type considered characteristic of the forma- tion asa whole. At the top of these finely laminated beds are sandy cherts and hard, dense white chert marking the top of the Beekmantown. Asso- ciated with these cherts and continuing upward for about 40 feet arc great numbers of the secondarily silicified cherts which have assumed MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XV ee Fic. I.—EXPOSURE OF LOWER BEEKMANTOWN LIMESTONE JUST ABOVE THE STONEHENGE MEMBER IN BRICKYARD, EASTERN EDGE OF HAGERSTOWN, MARYLAND. CLAY FOR BRICK MANUFACTURE RESULTS FROM THE WEATHERING OF THE PURER BEDS. Fic. 2.—BEEKMANTOWN LIMESTONE AT LEGORE QUARRY, LEGORE, MARYLAND. THE WEATHERED OUTCROPS OF THESE STRATA HAVE YIELDED NUMEROUS CEPHALOPODS. MaryYLaNnp GroLoaicaL SuRVEY 105 ‘ the form of a cauliflower. These mark the boundary between the Beek- mantown and Stones River limestones. As explained on another page, the secondary silicification necessary to form the cauliflower variety is supposed to have occurred in the time interval between the two formations when the Beekmantown rocks formed a land area. Sometimes the upper Beekmantown strata holding the Turritoma fauna do not weather as described above, but show the usual occurrence of smooth, rounded outcrops in which the fossils, although numerous, appear only as natural sections in the rock. Such exposures along the National Highway in the vicinity of Huyett, Maryland, have yielded the following species : Fossils of the Turritoma Zone in Maryland Dalmanella electra (Billings) Pleurotomaria ?? gregaria Billings Hormotoma gracilens (Whitfield) Turritoma acrea (Billings) Maclurites oceanus (Billings) Eccyliopterus disjunctus (Billings) Cyrtocerina mercurius Billings Trocholites internistriatus (Whitfield) Isochilina seelyi (Whitfield) Traces of this fauna, although always in poor preservation, have been noted at numerous places in Maryland, in fact Beekmantown strata exposed near the boundary line of the Stones River areas usually reveal one or more layers showing natural sections of these fossils. TopoGRAPHY AND ResipuaL Propuctrs.—The Beekmantown as a whole produces gently rolling country, but the lower Stonehenge member and a zone about 800 feet above the base of the formation give rise to very characteristic topographic features, which are of extreme importance in the mapping of areas in which rock outcrops are infrequent. These topographic features are the result of the various siliceous products left in the soil by weathering of the limestone. They are so distinctive that they become as important factors in the identification of the strata as the characters of the rock itself or of its contained fossils. In the absence of fossil remains or indeed of satisfactory rock 106 Tur CAMBRIAN AND ORDOVICIAN Deposits or MaryLAND outcrops it is often possible to determine the underground stratigraphy by the character of these surface residual products alone. In fact such criteria were alone available over considerable stretches of the rolling agricultural country with few rock exposures, that in this region at least, is characteristic of Beekmantown lmestone areas. On this account, although they have been mentioned incidentally and repeatedly in fore- going pages, it seems desirable to give here a connected discussion of the three most important residual products, namely, the siliceous shale frag- ments near the base of the formation, Cryptozoon and platy yellow chert near the middle, and the cauliflower chert at the top. The relatively pure limestone of the lower half of the Stonehenge member weathers rapidly and as its surface is not held up by some resistant residual a slight depression in the land surface results. On the other hand, the upper half of the Stonehenge member, with its sandy laminated strata weathering into a protective covering of thin siliceous shale fragments, forms hills corresponding in width to the outcrops and trending in the direction of the strike of its beds. As the Beekmantown everywhere in the Appalachian Valley of Maryland is highly folded, these hills assume the usual northeast-southwest direction of the folds and their development is so marked a feature that by plotting these elongated narrow hills, the upper Stonehenge member can be mapped in areas of few outcrops of the rock itself. When the succession is normal the lower Stonehenge limestone therefore occurs in a slight valley between the low hills of the upper Stonehenge on one side and the higher land on the other side formed by the chert weathered out of the upper part of the Conoco- cheague limestone. This topographic feature, however, is well developed only to the east of the Martinsburg shale belt. West of this belt the siliceous content of the laminated division of the Stonehenge is so much less that it has little effect on the topography. This topographic feature of the Stonehenge in connection with the line of hills next described makes it possible to map the complicated folds involving the Beekman town limestone without much doubt and has greatly aided in deciphering the geologic structure in areas of few outcrops. The Beekmantown rocks next or immediately succeeding following. the Stonehenge divisions are MaryYLAND GEOLOGICAL SURVEY 107 of a more soluble nature and therefore weather into lowland areas again. Therefore the broad area of folded Beekmantown limestones in which Hagerstown is located presents a succession of elongated highland areas alternating with usually broader lowland areas. This alternation in the topography is well shown in Hagerstown itself, where the hills passing through the town are composed of upper Stonehenge limestone and the low areas between them are underlaid by lower Stonehenge or by the over- lying Beekmantown limestone. The line of low hills formed by the upper member of the Stonehenge limestone is a characteristic feature of the Beekmantown topography only, as noted before, in the eastern half of the Appalachian Valley of Marylend, because west of the Martinsburg shale belt the siliceous nature of this member is not so well developed and consequently weathers much like the remaining portions of the Beekmantown. The marked topo- graphic feature of the western belt of outcrops is a line of hills composed of the chert derived from the Cryptozoon steeli zone of the formation which is unusually well developed in this part of the Valley. Here speci- mens of the Cryptozoon are very abundant, and as they silicify upon weathering, their remains leave considerable masses of chert in the soil However, the greater part of this residual material consists of yellow, platy, flinty chert formed by replacement of certain layers of the lime- stone. The Beekmantown limestone weathers so readily that the deter- mination of the geologic structure of the formation in many cases would be almost impossible were it not for this extensive development of Crypto- zoon and its accompanying chert. This chert zone is plotted on the map of the western part of the Valley where it gives a clue to the lower boundary of the formation and also aids in determining the structure. For example, the small synclinal area on the west flank of the larger synclinal area three miles northeast of Clear Spring is an interesting case of this zone’s value in determining structural relations. The cauliflower chert developed at the top of the Beekmantown does not occur abundantly enough or through a sufficient thickness of strata to form a topographic feature, but the unusual shape of these flinty objects is so characteristic that their presence in the soil is the surest 108 Tur CAMBRIAN AND ORDOVICIAN Drposrts or MARYLAND criterion in determining the dividing line between the Beekmantown and the overlying Stones River limestone. These cherts are believed by some students to represent in reality the physical evidence of the uncon- formity between these two great limestone formations. Unlike many other cherts they are not the result of present-day surface weathering, but appear to have been formed in the land interval between the two forma- tions. These cherts occur as a regular bedded deposit and their origin seems to be as follows: With the uplift at the end of Beekmantown time, weathering of the exposed limestones took place, resulting, as it does to-day, under favorable conditions, in a soil with more or less numerous chert fragments. Con- tinual exposure to waters bearing silica in solution caused a secondary silicification of these cherts by the formation of rosettes of silica over their surface. The rosette areas continued to grow larger and larger until the characteristic cauliflower shape resulted. The reason for the formation of such rosettes is obscure, but it is a fact that fractured fossils or pieces of chert will develop areas of rosette quartz along the fractured zones if subjected to the influence of silica-bearing waters. All of the chert at the top of the Beekmantown has not undergone secondary silici- fication into the cauliflower form. Fragments of platy chert representing the primary silicification stage may occasionally be noted with fracture zones penetrating into or entirely through them. The water with silica in solution will seep into these fractures and deposit the silica there first, thus starting a growth area which develops into the characteristic rosettes of the cauliflower variety. By this process a small fragment of platy or irregular chert by continual growth of the rosette areas will develop into specimens of the cauliflower variety a foot or more in diameter. Apparently the same process occurs in fractured fossils found in cer- tain siliceous shale formations, particularly of Silurian and Missis- sippian ages. For example, a crinoid column of say one-half inch in diameter, exposed to silica-bearing waters, will first receive a deposit of silica in its central canal and rosettes of silica will project from each end. The column is fractured by this process and each fracture line then MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XVI Fic. I.—NEAR VIEW OF BEEKMANTOWN LIMESTONE AT LEGORE QUARRY, LEGORE, MARYLAND. STRATA PENETRATED BY A SIX-INCH DIABASE DYKE (MARKED BY HAMMER). Fic. 2.—vIEW OF CONTACT BETWEEN THE BEEKMANTOWN (B) AND STONES RIVER (S) LIMESTONES ALONG THE SOUTH SIDE OF THE NATIONAL HIGHWAY AT WILSON, MARYLAND. THE ZONE OF CAULIFLOWER CHERT (C) IS WELL DISPLAYED AT THIS PLACE. MaryLanp GEoLoGicaAL SURVEY 109 becomes filled with silica which, with continual deposition, enlarges the original small column into a mass several inches in diameter. Usually in such cases the resulting mass is hollow and lined internally with crystals, thus forming a geode. Sometimes, however, it is solid, in which event a structure not unlike the cauliflower chert results. The general problem of silicification is most complicated and little is known yet of either its chemical or physical aspects. Why a certain limestone should, under past or present-day weathering, develop chert products which are so alike over large areas that they can be used in the determination of the bed, is not only an interesting question scientifically, but it is also of such geological importance as to merit the most detailed study. Another interesting feature in connection with the cauliflower chert is its occurrence, noted at several places, in a black shale, sometimes regu- larly bedded but again irregularly deposited, much resembling an ancient soil. Such a shale bed at the top of the Beekmantown may be seen in the cut along the National Highway just west of Wilson, Md. Cauliflower cherts are very abundant in this shale bed and its surface outcrop strews the ground with the irregular masses. However, they are not limited to this shale, for here, as well as at other places, the typical chert occurs in regularly bedded dolomite. Although discussed here in connection with the Beekmantown, the zone of cauliflower chert, if the above explanation is correct, should be regarded as basal Stones River. It might in reality be regarded as a basal con- glomerate formed, however, in a totally different manner from other conglomerates. Area Distrrpution.—The Beekmantown limestone with its basal Stonehenge member is the most widely distributed early Paleozoic forma- tion in Maryland, as its outcrop covers large areas in both the Appalachian and Frederick valleys where its strata weather rapidly into good soil and produce a géntly rolling country with excellent farm land. In the eastern belt of outcrop in the Appalachian Valley the formation is closely folded, occupying an area equal to half that of the Valley and 110 Tuer CAMBRIAN AND ORDOVICIAN Derposirs oF MAryLAND extending from a line passing through Security, three miles east of Hagerstown, to a northeast-southwest line west of Williamsport where a fault brings the limestone in contact with the Martinsburg shale. The broad expanse of Conococheague limestone in southern Maryland reduces the width of the Beekmantown here from a belt almost’ seven miles wide at the Pennsylvania state line to less than three at the Potomac. South of Hagerstown the Conococheague and Beekmantown limestones are intimately folded together, exhibiting characteristic Appalachian pitch- ing anticlines and synclines. The western edge of this belt is a fault line except at the extreme northern and southern ends where the normal sequence is resumed. This fault is clearly shown at Williamsport where the middle limestone of the Beekmantown may be seen in contact with the lower Martinsburg shale. North of Williamsport the displacement of this fault is greater and brings the Beekmantown in contact with the upper sandy portion of the Martinsburg. Infolded in this large area of Beekmantown are elongated, narrow bands of the purer limestones of the succeeding Stones River formation. In the area west of the Martinsburg shale plateau the Beekmantown limestone likewise occupies about one-half of this part of the Appalachian Valley, but here closely folding with the Conococheague limestone causes each formation to appear at the surface in elongated, more or less parallel bands. The continuity of these bands is broken in the northern part of the state by a transverse fault. West of the eastern base of North Mountain no rocks of Beekmantown age are exposed. The surface rock of a considerable portion of the Frederick Valley belongs to the red beds of Triassic age, but of the limestone portion of the valley about one-half is occupied by strata referred to the Beekman- town. These Beekmantown areas occupy in general the eastern half of this portion, although folding brings small areas to the surface in the western half. Two small areas just east of Catoctin Mountain are of interest because erosion of the red beds has proceeded far enough to expose the underlying Beekmantown strata. MaryLanp GEoLocicaL SuRVEY 111 East of the Frederick Valley on the Piedmont Plateau, narrow, elon- gated, infolded areas of limestone occur, only one of which is shown on the map because of its evident relationship to the limestone of the valley proper. Metamorphism has destroyed the evidence as to the age rela- tions of these limestones, although it is possible that they represent an eastern extension of the fossiliferous Beekmantown strata of the Frederick Valley. FREDERICK VALLEY LIMESTONES The considerable development of Early Paleozoic limestones east of Catoctin Mountain in the Frederick Valley and their economic value has long been known to geologists. As these deposits occur east of the Blue Ridge and are the easternmost unmetamorphosed Paleozoic strata known, the determination of their exact age relations is a matter of importance and interest. The Frederick Valley is bounded on the west by Catoctin Mountain, composed of Lower Cambrian sandstone and shale, and on the east by a range of low hills formed by pre-Cambrian schist. The length of the limestone area is about 30 miles and its maximum breadth about six miles. North of LeGore, Maryland, the limestones pass under cover of the Newark red beds, while at the Potomac they cross into Virginia where they again soon disappear under the red beds. This area has been studied by several geologists, but the most important work upon it was that of Keyes, who published his results in 1890 in the Johns Hopkins University Circular. His description of these rocks is as follows: “The beds have a mean dip of about 25 degrees to the east- ward. Along their western border they are covered by Triassic red sand- stones (Newark formation). To the east the limestones pass gradually into shales and slates, the whole forming apparently a conformable series. The limestones in great part are bluish in color, compact and heavily bedded ; but on approaching the shales they become more and more thinly bedded and very dark blue or nearly black, owing to the bituminous matter present. The latter, however, is driven off by burning, leaving a pure white lime. In places this lime rock is highly siliceous on account of the presence of a considerable amount of rather coarse quartz sand. 8 112 Tuer CAMBRIAN AND ORDOVICIAN Deposits oF MARYLAND This large amount of silica renders the rock unfit for the manufacture of lime, which at present is the chief use to which the Frederick Valley limestones are put. From the thin-bedded belt the limestone passes into a more earthy facies and grades into dark colored calcareous shales and these again into slates or into sandy shales.” Are aos WE INAV ANIA IIA IA \ls AAA! Re INN ISWS ‘ 7 Im\Z INIA 7 mV y Iw IAIN ‘ ~ - aN ARAN \ Ac O¢ T =\-1\~70 Ws} i SNe Vie VP nN x! yt 3 rae s\- MENTS Nita ! Pan !-7 NNN a ! ns ' (Te Pe Ue es t I TEIN NPN \r~ \ Fig. 12.—sTRUCTURE SECTIONS ACROSS FREDERICK VALLEY. C. East-west section through Frederick Junction. A. Devilbiss Bridge east through McAleer. D. East-west section through Buckeystown. B. Braddock Heights east through Frederick, SYMBOLS. Tn—Newark sandstone and shale. Of—Frederick limestone. Cl—Loudon formation. Tnc—Newark conglomerate, Ch—Harpers shale. Ac—Catoctin schist. Ob—Beekmantown limestone. Cw—Weverton sandstone. Keyes found a few species of fossils in these limestones which led him to suggest that the whole series was equivalent to the Chazy, Trenton, and Hudson River formations. The determination of the age and structure relations of the Frederick Valley limestones was a matter of MarYLAND GEOLOGICAL SURVEY 113 some difficulty, and the present author was fortunate in having this earlier work upon the subject even though he is unable to agree with some of the conclusions. Comparison of the four structure sections across the Frederick Valley, here presented as fig. 12 with that published by Keyes, will show that the present conception of the structure and stratigraphy differs radically. The lowest sedimentary rocks of this particular region are comprised in the Lower Cambrian quartzites, the Weverton sandstone and the succeed- ing Lower Cambrian Harpers shale exposed in Catoctin Mountain. Sugar Loaf Mountain, on the east, likewise is composed of Lower Cambrian quartzite. In the opinion of the writer the limestone series does not pass upward on the eastern side of the valley into Hudson River shales, but it is faulted against shales and schists which are of pre-Cambrian age. Along the western side of the Frederick Valley the limestones are covered by the conglomerate, red sandstone and shale of the Newark series except in two areas where stream erosion has cut deeply into and in places almost to the base of the underlying limestones. The structural relations of the Frederick Valley are so complicated that it would be difficult to unravel the stratigraphy were it not for the occa- sional presence of fossils. Determinable, though but rarely preserved, fossil remains have been noted at numerous places in the valley in two distinct kinds of rocks, namely, in dark blue thin-bedded strata, known locally as the building rock, and in massive, rather pure, blue to white limestone that is quarried for lime. The fossils in the quarry rock have been found distributed through several hundred feet of strata. They consist mainly of cephalopod shells which are closely related to lower Beekmantown species. The fauna found in the building rock consists of a brachiopod and a trilobite of types which are unquestionably of post Beekmantown age. By fossil evidence, therefore, the age of the quarry rock is established as older than the building rock. This conclusion is borne out also by the structural relations of the beds, the building rock being invariably infolded in the quarry rock. In all probability, the line of contact between the limestone which forms the floor of the valley and 114. nr CaMBRIAN AND ORDOVICIAN DeEposrrs oF MAryLAND the siliceous formations which form its elevated east and west boundaries, is in both cases a fault plane. There is little doubt as to the faulting on the east side, but the evidence is not so convincing on the west side. "The succession there may be normal, that is, undisturbed with the Beekman- town limestone lying unconformably on the Lower Cambrian Harpers shale. The Beekmantown Limestone All of the numerous quarries in the Frederick Valley operated for the burning of lime expose massive, rather pure, bluish limestones which hold fossils of Beekmantown age. The rock itself is not unlike that of the lower Beekmantown above the Stonehenge member in the Appalachian Valley, so that the use of the name Beekmantown for the quarry rock seems appropriate. It is even possible that the Stonehenge member is represented here, for in the outcrops of Paleozoic limestone in the western part of the valley, namely, along the trolley car track two and one-half miles northwest of Frederick, strata with edgewise conglomerates are well developed. Usually, in this part of the valley, these massive limestones are covered by Mesozoic red beds. However, in two places, erosion has removed the red beds so as to expose not only the quarry rock, but also the underlying Harpers shale. One of these is in a small area two miles south of Catoctin, the other a larger exposure just east of Braddock. Fossils were not observed in either of these areas, but the lithology of the limestone is precisely like that of the fossiliferous strata a short distance: to the east. Moreover, as shown on the map (pl. 1), an area of quarry rock just east of Braddock contains an infolded band of fossiliferous building rock. Throughout the central and eastern parts of the valley where the quarry rock frequently outcrops there can be no question regarding the Beekmantown age, for here fossils are not uncommon. Along the eastern edge of the valley just west of the pre-Cambrian schists there are outcrops of a massive light gray laminated limestone in which the laminae are much contorted and weather into a sandy shale somewhat resembling the shale fragments resulting from the disintegration of the upper Stone- henge member of the Beekmantown. Fossils have not been discovered in MARYLAND GEOLOGICAL SURVEY 115 these particular beds, but these laminated strata undoubtedly represent a part of the Beekmantown as developed in the Frederick Valley. The northernmost exposures of the Frederick Valley limestones occur at LeGore, Maryland, just before these strata disappear under the red beds. Extensive quarrying operations here have exposed a considerable section of closely folded and evidently repeated beds. The clue to the proper sequence is given by several bands of the normally overlying thin- bedded fossiliferous building rock that are infolded with the more massive Beekmantown limestones. At LeGore the building rock is immediately underlaid by about 100 feet of massive dark blue rather pure limestone in beds two to three feet thick, alternating with similar beds of lighter colored strata. Cephalo- pods of Beekmantown affinities are not uncommon on the weathered edges of these strata. These upper fossiliferous beds are separated by about 50 feet of massive light blue limestone with quartz grains, from a lower fossiliferous zone. This comprises several hundred feet of strata similar in lithology and fossils to the upper beds. The section then continues for several hundred feet which appear to be a repetition by folding of the strata just described. Many of these massive beds are very homogeneous’ and marble-like in character. The quarries at Frederick and to the south also afford excellent exposures of the upper beds of the massive lime- stone, but as the strata are little folded here, the exposed thickness is consequently slight. On account of their ready solubility, outcrops of these pure massive limestones appear only in lowland areas. They also leave no surface residual products such as the quartz or shale fragments of the building rock. The Frederick Limestone This new name is proposed for the strata in the Frederick Valley over- lying the Beekmantown limestone and containing a fauna probably of Chazyan age. The rocks are shown to advantage in numerous quarries and natural outcrops around Frederick. Fossils are of rare occurrence in these outcrops, but they may be found occasionally in the broad, thin slabs of which the stone fences of the valley are built. 116 Tur CamMbriaN AND ORDOVICIAN Deposits oF MARYLAND The Frederick limestone consists of thin-bedded dark blue argillaceous strata separating into layers usually less than two inches in thickness. On further weathering, these leave as a residual product in the soil, brownish-yellow shale-like fragments quite similar to the weathered Martinsburg shale of the Appalachian Valley. This limestone is often much crumpled and so seamed with quartz veins that the disintegration of -its strata leaves numerous fragments of white crystalline quartz in the soil. In freshly quarried exposures the Frederick limestone appears massive and dark blue, but slight exposure to the weather causes its separation into the thin flagstones so much used in this area for building fences and embankments that the local name of building rock is applied to it. Tt is less soluble than the associated purer Beekmantown limestone, so that in weathering it gives rise to hill topography which is in marked contrast to the lowland areas characteristic of the Beekmantown strata. The dark-blue color, thin platy layers of argillaceous composition, upland topography and residual quartz fragments distinguish it readily from the lighter colored, massive, purer rock referred to the Beekmantown. Although numerous exposures of the Frederick limestone may be seen in the vicinity of Frederick, perhaps the best place to view its contact with the underlying Beekmantown limestone is at the Tabler quarry where a distinct line of unconformity may be noted between the two formations. The thickness of the Frederick limestone is difficult to determine because it has no recognizable upper boundary such as the succeeding formation. However, in areas where it is infolded into the Beekmantown limestone, its thickness seems to be not less than 200 feet. "Such infolded areas are well shown in the quarries at LeGore, Maryland. Although of rare occurrence fossils can be found in this limestone more frequently than in the subjacent strata because the opportunities for collecting are more numerous. The natural outcrops of the rock seldom show organic remains, but it is only a matter of search along the stone fences of the Frederick Valley to discover fossils in the thin lime- stone layers of which most of them have been built. Five species have MARYLAND GEOLOGICAL SURVEY 3 117 been noted, only two of which are sufficiently preserved for specific description. These are Acidaspis ulrichi and Strophomena stosei, two new species and an undetermined species each of the genera Reteocrinus ?, Cameroceras and Isotelus. The prime interest of this fauna, like that of the underlying Beekmantown, is in its occurrence east of the Blue Ridge. This particular association of species is also noteworthy because neither the fauna itself nor the beds containing it can be correlated directly with any Appalachian Valley formation. However, the fauna suggests a Chazyan or early Mohawkian age with the possibility more in favor of the former. THE STONES RIVER LIMESTONE The purest limestones of the Shenandoah series are contained in the strata occurring between the underlying finely laminated pure and magnesian Beekmantown formation and the overlying argillaceous nodular Chambersburg limestone of Black River age. These pure lime- stones are correlated on lithologic, stratigraphic, and paleontologic grounds with the Stones River group or formation of the Central Basin of Tennessee. In Maryland the Stones River limestone rests unconform- ably upon the Beekmantown, the uneven contact being well marked by an extensive development of secondarily silicified chert known as “ cauli- flower ” chert. The Stones River was named and defined as a distinct group in 1855 by Safford, who based it on the limestones outcropping along the Stones River in the vicinity of Murfreesboro, Tennessee. The group includes the lowest rocks appearing at the surface in the Nashville dome of the Cincinnati axis. Safford, in his “ Geology of Tennessee ” (1869), aban- doned the term under the misapprehension that the Stones River rocks were equivalent to the Trenton of New York. Winchell and Ulrich, in 189%, revived the name, and later Ulrich and Hayes, in the description of the Columbia quadrangle of the U. S. Geological Survey, more com- pletely defined the group. . GrneERAL SEcTIoNs.—As recognized to-day the Stones River group in its type area in Central Tennessee includes the following formations: 118 Tue CamMBRIAN AND Orpvovic1AN Deposits oF MaryLAND Formations of Stones River Group in the Type Area, Central Tennessee Fee Lebanon limestone, flaggy, dove and shaly limestone..........--.++.0+- 120 Ridley limestone, massive subgranular, often cherty limestone..........- 80 Pierce limestone, shaly limestone crowded with bryozoans............+.-. 27 Murfreesboro limestone, heavy bedded cherty limestone (base not ex- POSER)... caves tee cee os park er aure d's SAS TER EW Hee RAE Nee Le ne ee ote oe aE TE 125 In the gorge of Kentucky River at and above Highbridge, Kentucky, which cuts through the oldest rocks to be seen in the state, the lower 200 feet of the bluffs are made by massive limestone strata representing Lebanon and Ridley members of the Stones River. In the Appalachian Valley, rocks corresponding in age, and also very closely in lithologic character with the typical Stones River, outcrop in periodically inter- rupted bands from Alabama to New York. In the valley of Hast Ten- nessee, where they attain a maximum thickness of more than 1200 feet. the lithologic facies and sequence that agrees best with the typical expres- sion of the formation is confined almost entirely to the western side of the valley. Here a twofold division may be recognized—a lower division of massive, mainly pure, dove limestone and an upper division of more argillaceous strata. The limestones in northern Virginia, Maryland, and Pennsylvania referred to the Stones’ River agree in all essential respects with these representatives of the group in the south. Here, however, the formation is divisible into three parts, of which the lower and upper thirds are of solid, massive, dove limestone and the middle third of more granular often cherty blue rock holding the fauna of which the large gastropod Maclurites magnus is the most characteristic member. The lower part is essentially equivalent to the Murfreesboro limestone, the middle division to the Pierce and Ridley beds, and the upper third to the Lebanon limestone of the type section. In the eastern half of the Appa- lachian Valley in Virginia and Tennessee the Maclurites magnus fauna occurs and attains its best development in a formation of argillaceous limestone—the Lenoir limestone. In this part of the valley the upper member is not present, so that here the Lenoir lies at the top of the beds that are strictly of the age of the Stones River. Beneath the Lenoir is a massive dove limestone formation, the Mosheim limestone, which is either ‘(WIZHSOW) NVIOIAOGNO ATYVEA— FT “DI 6161 ‘HOIATN O AAG ‘AHdVUDOADOAIVd NVOINAWNV HLYON ‘(AGLad LS) NVIOIAOGUO ATYVA—'ET ‘DI 6161 ‘HOIAIN ‘OA Ad ‘AHAVUNDOADOATVd NVOIWANV HLYON a ween rece ~ 2 ~Y ——-4 120 Tur CaMBRIAN AND ORDOVICIAN Deposits oF MaryLANpD distinctly older than the Murfreesboro limestone of the type area or it represents the basal part of that formation which does not reach the surface in central Tennessee. A weak, though typical representative of the Lenoir limestone fauna, is found in Maryland in the middle third of the Stones River and it is probable that the upper and lower thirds of the formations here developed represent all the remaining sedimentation of Stones River time. Although there is no continuous section in Maryland where the com- plete sequence may be observed, a generalized section in areas where the three divisions are well developed is as follows: Generalized Section of Stones River Limestone in Maryland meee Nodular, argillaceous strata of the Chambersburg limestone........ oes 3. Massive and thin bedded fine grained, pure, dove-colored limestone... 300+ 2. Massive pure limestone, blue to dark gray in color, compact, granular and o@litic, on weathering leaving black, blocky chert; contains the Maclurites magnus fauna....... cece cece creer e cece eee eeens 200+ 1. Massive and thin bedded, pure, dove limestone in the lower part interbedded with magnesian layers..........c.s cece een encase 600+ Light gray, finely laminated magnesian limestone of Beekmantown age, with cauliflower chert at top............ cc cece cee ceeenace This generalized section holds, also, for southern Pennsylvania, but from here northward the Stones River limestone diminishes in thickness due to progressive loss of the lowest beds by overlap. Between Green- castle and Chambersburg, Pennsylvania, the three divisions of the forma- tion have a combined thickness of about 1000 feet. At Carlisle the lowest division and a part of the middle are missing, leaving the formation only about 450 feet thick. Farther north at Harrisburg the middle member has been diminished by another hundred feet. Throughout the Lehigh Valley in Pennsylvania and its continuation in New Jersey, the Stones River is absent altogether. In eastern New York this formation is still absent until the upper Champlain region is reached where the Stones River interval is occupied by Chazyan limestones. The Middle Chazyan Crown Point limestone contains the Maclurites magnus fauna and thus offers a means of correlation with the more southern Stones River limestone. . MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XVII Fic. 1.—AN AVERAGE EXAMPLE OF THE CAULIFLOWER CHERT FROM THE BASE OF THE STONES RIVER LIMESTONE. VICINITY OF BOSTETTER, MARYLAND. Fic. 2.—TYPICAL NATURAL OUTCROP OF UPPER STONES RIVER LIMESTONE IN CLEARED FIELDS, ONE-HALF MILE WEST OF PINESBURG, MARYLAND. THE GROWTH OF CEDAR TREES ON THIS PURE LIMESTONE IS ILLUSTRATED. MarYLAND GEOLOGICAL SURVEY 121 LirHoLoGic CuaRAcTER.—The Stones River rocks in Maryland are in general heavily bedded dolomitic layers alternating with greater thick- nesses of relatively pure dove-colored limestones. In color and texture the purer rock varies from fine-grained dove to a dense black with the. dove-colored rock predominating. Many of the layers run as high in magnesia as the underlying Beekmantown limestone, but the Stones River formation differs in that at least a few pure dove limestone layers are found in almost every exposure. The pure liméstone is most abundant at the top of the formation, which portion therefore is most extensively quarried. Many of the layers throughout the formation and especially the purer strata are penetrated by the thin calcite strings belonging to the single-tubed species of the coral Tetradiwm, which, in connection with the smooth, homogeneous ground mass and color of the main rock, gives it a very characteristic aspect. Another method of distinguishing the Stones River from the Beekmantown lithologically lies in the char- acter of the soil to which each gives rise on weathering. The soil result- ing from the decomposition of the Beekmantown limestone is of a deep ted color, and generally contains a considerable quantity of broken chert. Stones River rocks, on the other hand, are practically free of chert except the middle division; and one soon learns to discriminate this chert from all the varieties formed in the decomposition of the Beekmantown limestone. Soil formed by decay of Stones River rocks seems to be particularly suited for the growth of cedar trees. Indeed, the presence of a consider- able number of cedar trees in an area of Ordovician strata is quite a teliable sign that the underlying rocks are of this age. Of course, this preference of cedars for Stones River areas is due primarily to the nature of the rock itself, in this case, the pure dove strata being cedar-bearing. The extensive well-known cedar glades of central Tennessee are located upon the pure, dove-colored Stones River limestone. PaLEONTOLOGY.—Dove limestones which make up the greater part of the formation do not as a rule afford well-preserved fossils, although traces of organic remains in the rock may be very numerous. In fact some of these pure limestone layers are crowded with gastropods, but 122 Tur CamBriIAN AND OrpovicIan Drposrrs or MARYLAND specimens cannot be broken out of the rock in recognizable condition. Their cross-sections indicate a general type of structure quite unlike and more advanced than the gastropods found in the underlying Beekman- town limestone. Two fossils, however, both easily recognized, may be found at almost any outcrop of this limestone. One is a coral formed of single tubes, quadrangular in cross-section, but commonly appearing more like calcite stringers in the rock than organic remains. This is the Tetradium syringoporoides described on a later page. The second fossil is a bean-shaped bivalved crustacean allied to Leperditia fabulites which occurs throughout the limestone. Other recognizable fossils occur, but as they are more limited in their stratigraphic distribution, details regarding them are reserved for the special discussions of the several divisions. Lower Stones River.—Although present in several bands of outcrop across Maryland, this portion of the Stones River is usually covered and the character of the rocks can be made out only from a few scattered out- crops. The best development is in the band of outcrop exposed just west of Pinesburg Station and running north almost to the state line. This same band of outcrop is exposed at Martinsburg, West Virginia. Here many of the layers, especially in the upper two-thirds of the member, show sections of undetermined gastropods and pelecypods and of the large ostracod Leperditia fabulites. In the quarries on the west side of the town which expose the lower 200 feet of the formation Ulrich reported certain weathered layers about 125 feet above the base of the formation, from which he collected the following fauna: Fauna of Lower Stones River Limestone, Martinsburg, West Virginia Girvanella sp. Solenopora compacta var. Small, undetermined monticuliporoid bryozoan Cyrtodonta n. sp. Matheria n. sp. Liospira cf. obtusa Lophospira cf. perangulata Lophospira n. sp. of the L. trochonemoides section Helicotoma ? n. sp. Orthoceras sp. undet. Small, with narrow septa Oncoceras ? sp. undet. Leperditia fabulites Conrad var. CAMBRIAN AND ORDOVICIAN, PLATE XVIII MARYLAND GEOLOGICAL SURVEY I.—VIEW OF EDGEWISE CONGLOMERATE IN STONES RIVER FORMATION 2% MILES Fic SOUTHEAST OF WILLIAMSPORT, MARYLAND. NESBURG STATION, MARYLAND. —VIEW OF QUARRY IN CHAMBERSBURG LIMESTONE AT PI Fic, 2. MARYLAND GEOLOGICAL SURVEY 123 Traces of this fauna have been found in Maryland, but neither these nor the specimens from West Virginia are thought well-enough preserved to warrant illustration and description. This lower division is about 600 feet thick and consists of massive and thin-bedded pure dove limestone interbedded, especially toward the base, with magnesian layers. Certain parts of the underlying Beekmantown limestone are much like these in lithic character, but the presence of bivalved pelecypod shells in the Stones River and their complete absence in the Beekmantown serves to distinguish the two formations. No well- exposed section of the Lower Stones River was found in Maryland, but at Martinsburg, West Virginia, the following section is more or less clearly exposed in quarries and nearby natural outcrops. Section of Basal Beds of Stones River Limestone at Martinsburg, West Virginia Feet Strata of Middle Stones River......... cece cece e cece eee e nent tenes Light to dark drab limestone banded with thin earthy or magnesian SGAMS) 4. pesdacsaly datitersnata-e Sacha de we sans SP eee be aries aos Yate os ead OF nar aa ere & 275 Strata like the above but less well exposed.......... ccc cee cee cence neces 200 Dark-gray to dove-colored, fine, even-grained pure limestone (quarried). 100 Similar finegrained, dove-colored limestone, increasing downward in magnesium: (quarried) 64 sad comes dee ws een bu ace gee le aden wage . 100 Section extends to the cherty top of the Beekmantown. 675 Railroad cuts along the Cumberland Valley Railroad north of Kauff- man, Pennsylvania, eight miles north of the Maryland line, show the gen- eral character of the division. This same band of outcrop continues south- ward into Maryland and a number of localities show small outcrops of the basal rocks. At Bostetter the very base of the formation is exposed at a low angle of dip, with the result that a considerable area here is covered with the cauliflower chert described under the discussion of the Beekman- town limestone. This cauliflower chert marks the base of the formation in the northern half of Maryland east of the Martinsburg shale belt, and it is present in all the bands of outcrop west of this belt. In the southern part of the area east of the shale belt, the Stones River rocks are poorly exposed and their basal beds are marked by edgewise con- glomerates quite similar to those of underlying formations. These con- 124 THe CaMBRIAN AND OrDovici1AN Deposits oF MARYLAND glomerates occur in place of the cauliflower chert which is so conspicu- ously developed elsewhere in the valley. Occasionally these basal edgewise conglomerates become silicified, leaving very interesting chert blocks in the soil exhibiting the conglomeratic fragments as pure chalcedonic silica, or in some cases showing them leached out of the rock entirely. Middle Stones River—The middle part of this limestone is so readily distinguished from the upper and lower divisions by its fossils and lith- ology that it might well be ranked as a distinct formation. The Middle Stones River differs conspicuously from the other divisions in the pres- ence of massive beds of dark, subgranular limestone interbedded with the more typical dove-colored, fine-grained, pure limestone. Fine-grained, pure, fossiliferous limestone weathering so as to show numerous bands of black chert form a characteristic part of this division. In the absence of outcrops an easily recognized criterion for the determination of the middle division is the presence of small blocks of chert in the soil. This chert is usually black, at least the inside of the blocks when broken show up as black. Furthermore, the Middle Stones River is generally more fossiliferous than the other divisions and the typical fossil, the large coiled gastropod shell Maclurites magnus, can usually be found in it after a little search. The best outcrops for fossils of the Middle Stones River are in the quarries around Chambersburg, Pennsylvania, where the fauna listed below was collected and determined by Ulrich (Chambersburg-Mercers- burg Folio). All of these species, however, have been noted in the corresponding band of outcrop in Maryland, although all have not occurred at a single place. Fauna of the Middle Stones River Limestone in Southern Pennsylvania and in Maryland Tetradium syringoporoides (Ulrich) Hebertella borealis (Billings) Hebertella vulgaris (Raymond) Dinorthis platys (Billings) Bucania suicatina (Emmons) Maclurites magnus (Lesueur) Lophospira bicincta (Hall) Ampys halli (Billings) Leperditia fabulites (Conrad) var. “HHALIY SANOLS AXddN—'OT ‘dL 5 6161 ‘HOININ OA AG ‘ ‘AHdVUDOAOOATVd NVOIWANV HLYON ‘(VNOVA ., SONDVW SHLIENIOVN ,,) YIAIU SANOLS FIaqIW—'eT ‘ol ANY TT se: XA LEXLIL, ( i Laelia 6161 ‘HOIN1N ‘0 -F 4a ‘AHdVuUOOADOATVd NVOIMAINV HLYON 126 Tue CAMBRIAN AND ORDOVICIAN DEPOSITS OF MAaRryLAND This fauna is correlated with the Middle Chazy or Crown Point lime- stone of New York and the Lenoir limestone of southern Virginia and Tennessee, in each of which most of these species occur. Upper Stones River.—The upper division consists of very pure, thin- bedded, dove-colored or pearl gray homogeneous limestone which is quite frequently exposed because most of the quarries are in this rock. The large quarry at Pinesburg Station exposes a considerable thickness of these pure upper beds. Here also sections of numerous fossils may be noted, but the rock is so homogeneous that the specimens cannot be broken out, and it weathers in such a manner that the fossils are not left in relief on the surface. The only species which can be obtained in any fair state of preservation is the characteristic Stones River single tube coral Tetradium syringoporoides. A conspicuous topographical feature of this portion of the Stones River particularly is the occurrence of numerous sinks along its line of outcrop. However, conditions favoring the formations of such sinks occur also in the lower portion of the Stones River. AREAL DISTRIBUTION 4ND TopoGRAPHIC ForM.—The outcrops of the Stones River limestone in Maryland are confined to the Appalachian Valley and cross the state in five distinct bands, three of which occur east of the shale belt of the middle portion of the Valley, and two to the west. The strata of the three eastern belts are not as highly folded as those to the west and the areas of outcrop are therefore wider. Hach of these belts occupies a nearly level lowland broken only by low hills formed by the cherty middle division. In the northern half of these three belts the chert and resulting low hills of the Middle Stones River are especially well developed. In Maryland this middle portion has been noted in out- crops at many points. The residual black chert is frequently so abundant in the soil that it leaves its impress upon the topography in the form of low hills arranged according to the geological structure. This is illus- trated in an area just south of the Pennsylvania state line and directly north of Hagerstown where the outcrop of the Middle Stones River cherty limestone is plainly indicated by the low hills elongated in a MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XIX Fic. I1.—PHOTOGRAPH SHOWING SUCCESSION OF SINKS ALONG THE BAND OF OUTCROP OF THE STONES RIVER LIMESTONE, ONE-HALF MILE SOUTH OF WILSON, MARYLAND. THE ROAD TO THE EAST FOLLOWS THE CHAMBERSBURG LIMESTONE. r Fic. 2.—NEAR VIEW OF A SINK FILLED WITH WATER. MaryYLAND GEOLOGICAL SURVEY 127 general northeast-southwest direction, but aligned to coincide with the general structure of the region. In this same area the zone of cauliflower chert at the base of the Stones River is also well developed, but forms no special topographic features. With weathering, however, the chert breaks up into smaller and smaller fragments so that its presence is not a detriment to the soil. One of the two western belts lies just west of the Martinsburg shale area and the second is a short belt cut off by faulting in the middle of the state and occupies the center of the western half of the Great Valley. Each of these more western belts is quite narrow, because the rocks are steeply inclined. Here too the Middle Stones River cherty limestone is not as clearly developed as in the more eastern areas. Rocks outcrops usually are few, and the formation everywhere gives rise to excellent farm land soil. Fauna OF THE STONES River In Marytanp.—The fossils of the Stones River limestone in its typical development in the Central Basin of Tennes- see have not received as much attention as those of the younger Ordovician formations, but a considerable fauna from each of its divisions has been collected and awaits description. The faunas of the corresponding rocks in the Champlain Valley have been quite fully described by Raymond in recent years and Middle Chazyan faunas have been recognized farther south in the Appalachians. In Maryland the middle division of the Stones River limestone contains enough Middle Chazy species to make it reasonably certain that these strata represent the same time interval. The massive, purer dove and magnesian limestone of the upper and lower divisions of the Stones River in Pennsylvania and Maryland are not favorable for the occurrence of well-preserved fossils. These two divisions do not weather into chert, and the best specimens from massive limestone are always to be found in the residual cherts. The single-tubed coral, Tetradium syringoporoides, and the bean-shaped ostracod, Leperditia fabulites, are abundant throughout the Stones River and may be found at almost all exposures. The other seven species here described are all 9 128 Tur CamMBRIAN AND OrpDovICcIAN DeEposits oF MAaryLAND species occurring in the Middle Chazy of the Champlain Valley. The Maryland Stones River fauna and its occurrence elsewhere is listed below. FAUNA OF THE STONES RIVER LIMESTONE IN MARYLAND Stones River of Maryland Lenoir | Middle lime- | Chazy of stone of} Champlain Lower |Middle| Upper | Ten: | Valley Tetradium syringoporoides Ulrich......... * * Dinorthis (Plaesiomys) platys eUiaas FHebertella borealis oa : Hebertella vulgaris Raymond.. Sau site? Bucania suleatina (Emmons).............- Lophospira bicineta (Hall).............0.. x6 tie Maclurites magnus Lesuenr.. : ball) Se * bub # Ampysz (Lonchodomas) halli Billings . 3 Leperditia fabulites (Conrad) var.. gaia. OKT [ek EERE! ¥* * The lower and upper division of the Stones River in Maryland, par- ticularly the latter, frequently exhibit layers crowded with gastropods and pelecypods. These show at the surface as natural sections and weather away as fast as the rock. Without a knowledge of the fauna of the similar dove limestone of the Stones River elsewhere, it is impossible to identify such natural sections with certainty. The areas of the Stones River limestone east of the Martinsburg shale belt have yielded few fossils because the rocks weather into a deep soil and outcrops are consequently infrequent. The boundaries of these areas have in most cases been determined by the occurrence of the basal Stones River cauliflower chert zone. In northern Maryland, the broad folded area of this formation just northeast of Maugansville and another a mile northwest of the same place show the best development of the Middle Stones River limestone with the characteristic chert hills left by its weathering. In this chert all of the fossils in the above list have been noted. West of the shale belt the band of outcrop starting at Pinesburg Station and going east of north through Wilson to the state line affords numerous outcrops of the dove limestone of the lower and upper divisions. Some of the layers in the Upper Stones River at Pinesburg Station are MARYLAND GEOLOGICAL SURVEY 129 crowded with Tetradium syringoporoides, while Leperditia fabulites and several species of undetermined shells occur in great number in other beds. THE CHAMBERSBURG LIMESTONE Most students of Appalachian stratigraphy have recognized a so-called transition zone of argillaceous limestone between the massive limestones of the Shenadoah group and the overlying great shale formation, the Martinsburg shale. These argillaceous limestones are thin bedded and quite fossiliferous in comparison with the underlying and overlying strata. They were classed as the closing phase of the Shenandoah group and their contained fossils established the Ordovician age of the upper part of that group. As their lithologic character is clearly enough intermediate between that of the underlying pure and magnesian limestones and the typical shale group above, it was natural to believe that they were really transition beds. However, detailed comparison of the faunas of these argillaceous beds in different parts of the Appalachian Valley in recent years has shown that these strata are either not transition beds at all or that the supposed transition occurred at widely different times in dif- ferent parts of the valley. The fossils showed that as’a rule shale deposi- tion set in much earlier in the eastern bands of the Appalachian Valley than in the western. Also that these dates varied considerably even in north and south directions. The “ transition ” beds when closely studied proved to represent formations of totally different ages in various parts of the valley and that stratigraphic breaks, sometimes of considerable extent, commonly separate them from both the underlying and overlying strata. For example, in the eastern bands of the valley of east Tennessee this argillaceous limestone phase of deposition is the Lenoir limestone of middle Chazyan age, while at the western side of the valley the limy beds just under the first shale are late Trenton in age. Again, in southern Pennsylvania the Chambersburg limestone of Black River age directly or immediately precedes the Ordovician shale group in the eastern or Cumberland Valley, whereas in central Pennsylvania the shale is under- lain by uppermost Trenton. The basal part of the shale itself varies correspondingly in age from upper Chazyan to Utica. 130 «Ture CAMBRIAN AND ORDOVICIAN Deposits or MaryLaNnpD In Maryland, as in southern Pennsylvania, the fossiliferous, thin- bedded limestone with argillaceous partings, formerly regarded as the uppermost division of the Shenandoah group, is now called the Chambers- burg limestone, so named by Stose from outcrops in the vicinity of Chambersburz, Pennsylvania. This limestone is subject to great varia- tions not only in thickness, but in the character of the rocks from place to place along the strike and across it. The rather broad expanse in southern Pennsylvania exposing Cambrian and Ordovician strata exhibits many outcrops of Chambersburg limestone. This is particularly true in the ‘Chambersburg and Mercersburg quadrangles in Pennsylvania where good collections of fossils have been made and numerous sections of the strata were studied. This broad area of outcrop is divided by a wide synclinal belt of Martinsburg shale that continues southward through Maryland into Virginia and lies in a continuation of the Massanutten syncline. As the towns of Chambersburg and Mercersburg are located respectively in the eastern and western belts, it has been found convenient to term these two belts of outcrop the Chambersburg and Mercersburg troughs. The very different composition and thickness of this formation in the two troughs has been used by Ulrich in his Revision of the Paleozoic Systems as a striking illustration of the instability of the continental floor during Middle Ordovician time. A résumé of these differences is presented under the discussion of the sections. LitHoLocic CHARAcTER.—The Chambersburg limestone as a whole is characterized by thin-bedded, fossiliferous, dark-blue, argillaceous limestone with clayey partings. Many of its layers upon weathering have ‘a tendency to break up into rounded cobblestone-like fragments. This “ cobbly ” nature of the weathered outcrop is so noticeable and character- istic of the formation that it may be safely employed in the discrimination of this limestone. In natural or artificial cuts exposing the weathered and unweathered zones of the limestone a great abundance of cobblestones at the surface may always be noted. Roads which happen to pass along the strike of the cobbly beds where these are highly tilted often clearly show the arrangement of the cobblestones in definite thin-bedded layers. MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XX Fic. I—TYPICAL EXPOSURE OF THE ECHINOSPHERITES BED OF THE CHAMBERSBURG LIME- STONE SHOWING CHARACTERISTIC COBBLY EFFECT. RAILROAD CUT AT PINESBURG STATION, MARYLAND, Fic. 2.—TYPICAL OUTCROP OF STEEPLY DIPPING CHAMBERSBURG LIMESTONE ALONG ROAD BETWEEN PINESBURG AND PINESBURG STATION, MARYLAND. MARYLAND GnoLoGIcaAL SuRVEY 131 The cobbly effect is caused by the clay partings in the limestone cross- ing it at a high angle so that weathering breaks up the solid limestone into rounded fragments. Also concentration of the lime in weathering and the relative facility of its loss by the more clayey parts has much to . do with the formation of the cobbles, as suggested by Ulrich. Fresh exposures, as in quarries, indicate these partings very obscurely. The limestone then appears massive and solid and exhibits regular bedding planes five or six inches apart. The change from the fresh, massive limestone to the cobblestones is well shown in railroad cuttings where the surface outcrop capping the fresh cutting is preserved. sw NE Strasburg.Va Martinsburg Pinesburg Mason-Dixon Greencastle Chambersburg 7 i t i ! i ae Se Y, SEE eS Nidelites bed CEE vel CE Ses % a Sinan See Fic. 17.—DIAGRAMMATIC SECTION OF CHAMBERSBURG LIMESTONE FROM CHAMBERS- BURG, PA., TO STRASBURG, W. VA. Although dark blue nodular limestone weathering cobbly constitutes the greater or at least the most conspicuous part of the Chambersburg formation in Maryland, other types of rock are widely developed and often exposed in the continuation of the outcrop belts to the north and south. These strata consist of interbedded thin calcareous shales and shaly limestones, thin-bedded, dark: gray limestone, and bluish grano- crystalline limestone. All these strata form a composite unit that is decidedly different from any of the underlying limestone formations. In Maryland the thickness of the Chambersburg limestone does ‘not exceed 300 feet; in southern Pennsylvania it reaches a maximum of 800 feet, although at the type exposure around Chambersburg, Pennsylvania, it is about 500 feet in thickness. This great variation is expressed in the 132 Tur CAMBRIAN AND ORDOVICIAN Deposits oF MaryLanp diagram on page 131, which shows that the diminished thickness in Maryland is due mainly to the absence of the lower divisions. AREAL DistRisuTion.—The area of outcrop of the Chambersburg lime- stone in Maryland is less than that of any other formation west of the Blue Ridge. Faulting along the east side of the Martinsburg shale belt has cut out the Chambersburg limestone everywhere in this part of the valley except in the very northern part of the state, and a very small patch in the great bend of the Potomac River at the southern edge. West of the shale belt the Chambersburg outcrops in an almost con- tinuous band extending from Pinesburg Station northward to the Penn- sylvania state line. West of this there is a second band of outcrop which, however, is cut out by faulting before half the state is traversed. The outcrops east of the Martinsburg shale belt give very little idea of the formation, and in fact its presence can be recognized only by a few traces of cobbly, dark-blue limestone showing here and there along the roads and in the fields. These exposures are so incomplete that it is impossible to work out any adequate idea of the sequence and character of the beds. The few exposures, however, indicate the presence of the. Echinospherites and Nidulites beds described below. The two lines of outcrop in the western half of the valley afford a better opportunity for the study of the formation. At Pinesburg Station a good exposure of the rocks may be seen, particularly the Echinospherites bed. The road running north from Pinesburg Station to Pinesburg passes along the strike of these rocks and numerous outcrops may be seen on either side of it. At Wilson the Echinospherites bed is not so well exposed, but the overlying Nidulites bed is well shown in the bluff overlooking Conococheague Creek. North of this is a rather broad area of the forma- tion, but here the rocks are hidden to a great extent by recent stream gravels. The line of outcrop west of the Pinesburg-Wilson area extends only half way across the state on account of faulting, and exposures are extremely few and poor throughout its length. Fauna Zones.—The researches of Ulrich in the Appalachian Valley of southern Pennsylvania, in which the present writer had an opportunity MarRYLAND GEOLOGICAL SURVEY 133 of assisting, have shown that the Chambersburg limestone can be divided into six faunal divisions or members. These members vary greatly in thickness from place to place, but retain their lithologic and faunal characters with little change. At no place is the composite section shown In the columnar section developed, but the strata shown here represent all the sedimentation so far as known, of Chambersburg age. These six divisions, which with one exception have received faunal designations for convenience of description, are as follows: Divisions of Chambersburg Limestone in Pennsylvania and Maryland Feet 6. Greencastle bed. Heavy bedded impure limestones.............+-05 0-200 5. Christiania bed. Thin bedded calcareous shales and shaly limestone. 0-270 4. Nidulites bed. Compact dark grey thick and thin bedded limestone. .200-300 3. Echinospherites bed. Dark blue argillaceous cobbly limestone...... 40- 50 2. Tetradium cellulosum bed. Fine grained dove and subgranular lime- SCONE: Ada auaiidk se ome dah Ohare ain aeanaw ad Malone Wel ere 0-200 1. Caryocystites bed. Bluish coarsely crystalline to subcrystalline lime- StONG wna cciecrsewecseacasees {SSW $6 INSTT EREN EK OE SSR Ye EES 0-175 The lithologic and faunal characteristics of these divisions are described in the following paragraphs: Caryocystites Bed—_The lowest division of the general time scale rep- resented in the typical exposures of Chambersburg limestone consists ox dove-colored and other limestones. This division contains the Tetradium cellulosum fauna and is clearly of Lowville age. West of the Martinsburg shale belt in Pennsylvania, the several bands of Chambersburg limestone exposed in the lowland area between the northern and southern offsets of North Mountain contain a well-defined and easily recognized lentil of bluish crystalline limestone reaching a maximum thickness of 175 feet. This bed wedges in between the Lowville division of the Chambersburg and the underlying top of the Stones River. The abundant occurrence of a cystid plate of the genus Caryocystites and its apparent restriction to this division makes the name Caryocystites bed appropriate. The bands of outcrop containing this bed are not exposed in Maryland, but are prob- ably buried under the younger strata of North Mountain and areas to the west. ‘(HITIAMOT) BAIN NOVIA aAMOT—'6T “OLA ‘(INQ0Td) NVAZVHO UiddN— BT “SIA ‘ * x 6161 ‘HDININ ‘0 Ad ‘0101 ‘HOINTN ‘O A Ad AHdVuUNO0ADOATVd NVOIMANV HLYON ‘AHdVUDOADOATVd NVOINANV HLYON 7 = Bee, Pos ID) “QV ee Nv N ae Orn “NS c N —e A fo Wages Bel ae wf ge / MaryLanp GroLogicaL SuRVEY 135 Fossils are rare in the lower two-thirds of the Caryocystites bed, but a fauna of over 50 species has been collected from the upper third, particu- larly from the upper 8 or 10 feet. As it is unlikely that this bed will ever be found exposed in Maryland, it was thought sufficient for present purposes to describe and illustrate only enough of its species to show its general faunal character. It contains such typical Chazyan brachiopods as Camarotoechia plena (Hall) and Hebertella vulgaris Raymond, with species of other classes indicating a similar early age in association with a few bryozoans and other fossils that have been found elsewhere only in Black River deposits. The determination of the age of the bed would therefore seem to be uncertain, but as it occupies the position between the earliest Black River (Lowville) formation ‘and the latest Stones River division which elsewhere is filled by Upper Chazyan deposits with similar faunas, it is believed advisable to refer the Caryocystites bed to the Chazyan. On the other hand, since the main part of the fauna is de- veloped only in the upper beds, it is possible that the entire division is of Chazyan age and that the upper part contains an earlier appearance of species commonly found elsewhere in the Black River. The fauna from this bed, as identified by Ulrich, is listed below. This faunal list, as well as others of the Chambersburg limestone which follow, is introduced only to give a general idea of the life characteristics of the various beds. Com- plete lists of each division can only be published when a monographic study of the Chambersburg faunas has been finished, a work which is far beyond the scope of the present volume. To give some idea of this fauna the specifically determined forms of the following list ure described in this volume. Fauna of the Caryocystites Bed, Chambersburg Limestone Solenopora compacta (Billings) Columnaria halli Nicholson Tetradium columnare (Hall) Carabocrinus sp. (plates) Caryocystites sp. (plates) Anolotichia sp. Nicholsonella cf. N. laminata Batostoma cfr. B. magnoporum 136 Tue CamBRIAN AND OrpDovicIAN Deposits oF MaryLaNnD Hemiphragma irrasum (Ulrich) Helopora divaricata Ulrich Rhinidictya fidelis Ulrich Pachydictya cfr. P. robusta Escharopora confluens Ulrich Graptodictya sp. (reticulate) Chasmatopora reticulata (Hall) Chasmatopora sublara (Ulrich) Hebertella borealis (Billings) Hebertella vulgaris Raymond Hebertella bellarugosa (Conrad) Rafinesquina champlainensis Raymond Leptaena charlottae Winchell and Schuchert Plectambonites sp. Camarotoechia plena (Hall) Zygospira recurvirostris (Hall) Ctenodonta cf. C. gibberula Cyrtodonta sp. Gonioceras chaziense Ruedemann Leperditia cf. L. fabulites Isochilina cf. I. gracilis Bathyurus sp. Amphilichas cf. trentonensis Tetradium cellulosum Bed.—One of the most widespread Paleozoic formations of North America is the dove limestone of early Black River age known as the Lowville limestone in the New York section. This formation has received various names in different parts of the country, but its fauna, and even its lithology, is unusually constant throughout an area extending from southern Canada to Alabama and from the Appa- lachians to the Mississippi River. The coral Tetradiwm cellulosum, dis- tinguished by its colonies composed of small bunches of four-sided tubes each with four septa, is the guide fossil of the formation. In the Cham- bersburg limestone, the Lowville division of the general time scale, or the Tetradium cellulosum bed, as it is here called, is present locally and sometimes reaches a thickness of as much as 200 feet. As indicated in the sections on other pages, it usually consists of fine-grained, dove-colored limestone with some subgranular beds. In southern Pennsylvania the Lowville forms the basal member of the Chambersburg limestone in the area between Chambersburg and the Maryland state line. It is present also in the Mercersburg belts but in these it rests on the Caryocystites bed. If represented at all in northern Maryland, it is so thin as to be negligible. ‘ MaryYLAND GEOLOGICAL SURVEY 137 The fauna of this zone, as represented just north of the Maryland state line, contains 15 described species, six of which are characteristic Lowville fossils and the rest Black River forms. The gastropods Helico- toma planulatoides Ulrich and Omospira alexandra (Billings) are par- ticularly characteristic species of the upper Lowville, but the coral Tetradium cellulosum, found everywhere, is the best guide fossil. The ‘list of species discovered by Ulrich in this bed in southern Pennsylvania a few miles north of the Maryland line is as follows. Only traces of the Louisville rocks and faunas can be found in Maryland and for that reason only the fifteen specifically identified faunas of this list are described. Fauna of the Tetradium cellulosum Bed, Chambersburg Limestone Camarocladia rugosum Ulrich Beatricea sp. Streptelasma profundum (Conrad) Tetradium cellulosum (Hall) Clieiocrinus sp. Orbignyella wetherbyi (Ulrich) , Strophomena cf. 8. emaciata Zygospira recurvirostris (Hall) Protorhyncha sp. Ctenodonta gibberula Salter Cyrtodonta sp. Helicotoma planulatoides Ulrich Helicotoma verticalis Ulrich Lophospira cf. L. procera Omospira alexandra (Billings) Clathrospira sp. Eunema cf. E. salteri Orthoceras sp. Leperditia fabulites (Conrad) Leperditella tumida (Ulrich) Isochilina cf. I. gracilis Isochilina cf. I. ottawa Macronotella ulrichi Ruedemann Drepanella macra Ulrich Aparchites sp. Primitia sp. Kloedenia sp. Isotelus sp. Pterygometopus callicephalus (Hall) Ceraurus pleurezanthemus Green ‘(MOIMSWWIN) UIATY MOVIE tadan— TZ “OLY *‘(Hva0ooad) AHAIY MOWIA AIddIW—0Z “OIL ~ 6161 HORVIN OH Ag “AHAVUOOADOATVd -- oes NVOIMANV HLYON 6161 ‘HOIN1N ‘0 3 Ad ‘AHdVUOOADOA 1Vd NVOIMANV HLYUON = th Sees ee? i se au we PSRs ain - =m BEUE pa Oe ae co pF AAS BAU N Pt} yy 7 7 ; a MARYLAND GEOLOGICAL SURVEY 139 Echinospherites Bed.—The massive, pure, dove-colored strata of the Stones River limestone are followed in Maryland by dark blue argillaceous cobbly limestone which is never over 50 feet in thickness. In fresh out- crops, such as in the railroad cut at. Pinesburg Station, Maryland, this limestone appears quite massive, but close inspection shows thin, shaly seams dividing the main mass of the rock into dark blue strata. Upon weathering these strata give rise to rounded pieces much resembling cobble stones. This feature is especially characteristic of the Echinospherites bed, although other divisions of the Chambersburg limestone exhibit similar strata. This bed contains a few highly fossiliferous bands which have yielded, in Pennsylvania outcrops, a fauna of about 27 species shown in the fol- lowing list published by Ulrich. Of these the ball cystid Lchinospherites is the most abundant and its remains may be found at almost every out- crop of the bed. Brachiopods and bryozoans of Black River types are associated with this cystid, although specimens are much less abundant. Numerous exposures of this bed occur in the line of outcrop from Pinesburg Station northward through Wilson to the State line, the best places for fossils being in the Western Maryland Railway cut at Pines- burg Station and the bluffs overlooking Conococheague Creek at Wilson. In southern Pennsylvania excellent exposures of this bed are found in the railroad cut at Kauffman and one mile northwest. Excepting the charac- teristic fossil Echinospherites, the fauna of this bed seems most closely allied to the upper Black River Decorah shale of the Mississippi Valley and for this reason its age is placed as late Black River. The species in the following list marked with an asterisk have been found in Maryland: Fauna of the Echinospherites Bed, Chambersburg Limestone Licrophycus cf. L. ottawaense Lockeia sp. *Receptaculites occidentalis Salter Ischadites sp. Orocystites ? sp. Raphanocrinus ? sp. *Hchinospherites aurantium americanum Bassler *Helopora spiniformis Ulrich 140 THE CAMBRIAN AND ORDOVICIAN Deposits or MaryLAND *Rhinidictya neglecta Ulrich Escharopora cf. ramosa *Prasopora insularis Ulrich *Hemiphragma irrasum (Ulrich) *Dianulites petropolitanus Dybowski Dalmanella testudinaria small variety *Dinorthis pectinella (Emmons) *Pianodema subaequata (Conrad) *Rafinesquina minnesotensis Winchell *Rafinesquina minnesotensis inquassa (Sardeson) Rafinesquina sp. Strophomena cf. 8S. filitexta Plectambonites sp. Plectambonites pisum var. *Hebertella bellarugosa (Conrad) Triplecia (Cliftonia) simulatrix Bassler Leperditia cf. L. fabulites Pterygometopus cf. P. schmidti *Ampyx (Lonchodomas) normalis Billings The Echinospherites and Nidulites beds are well developed in all the sections of this area, but the considerable thickening of the Christiania bed north and also south of Maryland is a second interesting feature. Finally, the occurrence of the Greencastle bed only in the area extending from the Mason-Dixon line northeast to beyond Chambersburg shows that local depressions in an area can receive sufficient sedimentation rep- resenting a hiatus which would otherwise hardly be suspected. In these various sections the Upper Stones River below and the Sinuites zone at the base of the Martinsburg above, form two datum planes which are recog- nized without difficulty. Nidulites Bed.—The Nidulites bed is the most conspicuous division of the Chambersburg in Maryland and forms the main part of the outcrops of the formation both east and west of the Martinsburg shale belt. The heaviest limestones of the formation are included in this bed which, as a rule, tends to weather in smooth, rounded outcrops like the underlying massive limestones of the Stones River and Beekmantown formations, instead of the usual cobbly layers. Cobbly layers do occur in this bed and their weathered outcrops have much the appearance of the underlying Echinospherites bed. In such cases a brief search will reveal the occur- MaryLanD GEOLOGICAL SURVEY 141 rence of the characteristic fossil of the Nidulites bed, Nidulites pyri- formis, a pear-shaped organism one to two inches long, with the surface marked by sharp ridges forming polygonal spaces a millimeter in diam- eter. This fossil does not reappear in the section until the Greencastle member is reached, but the latter has not been identified in Maryland. These NVidulttes are found throughout the 200 to 300 feet of thickness of the bed, but they are most abundant near the middle and the top. The different aspects of this fossil as seen on weathered surfaces of the lime- stone are shown on plate XLVI. Associated with the Nidulites and in equal abundance is a peculiar hemispherical or subglobular bryozoan-like organism described as Diplotrypa ? appalachia in this volume. A fauna of about 40 species has been collected and identified by Ulrich from the excellent exposures of the Nidulites bed in Pennsylvania, but the outcrops in Maryland have afforded only a portion of these. With the exception of the exposures of the bed along the bluffs overlooking Conoco- cheague Creek at Wilson, Maryland, its outcrops in the state are usually weathered edges of the highly tilted strata which do not as a rule afford good fossils. Cross-sections of the Nidulites and Diplotrypa can, however, be found in practically every exposure. So far as is known this bed and the overlying Christiania and Greencastle beds are not represented in the geological column elsewhere in North America. As the Sinuites bed at the base of the Martinsburg shales contain a fauna of early Trenton age and as the Echinospherites bed underlying the Nidulites bed contains an assemblage of species much like the upper part of the Decorah shales of the upper Black River, these three intervening divisions should be of latest Black River or earliest Trenton. In terms of the New York section these three divisions would represent an age between the top of the Black River and the base of the Trenton. The species marked with an asterisk are described in this volume. Fauna of the Nidulites Bed, Chambersburg Limestone Palaeophycus sp. *Nidulites pyriformis Bassler New genus of Amygdalocystidae New genus of Pleurocystidae Bolboporites sp. 142 Tum CaMBRIAN AND ORDOVICIAN Deposits or MaryLAND Carabocrinus sp. (plates) Porocrinus sp. *Diplotrypa appalachia Bassler Stromatotrypa sp. Mesotrypa ? sp. Stictoporella ? sp. *Prasopora contigua Ulrich Hemiphragma cf. irrasum *Corynotrypa inflata (Hall) *Corynotrypa delicatula (James) *Orthis tricenaria Conrad Plectorthis aff. P. whitfieldi Dalmanella testudinaria var. Pianodema cf. P. subaequata *Scenidium anthonense Sardeson Strophomena cf. S. filitexta Rafinesquina cf. R. incrassata Leptaena sp. Plectambonites cf. P. pisum Plectambonites sp. Triplecia (Cliftonia) simulatrix Bassler Leperditia cf. L. fabulites Ampyz cf. A. normalis Illaenus sp. Pterygometopus cf. P. callicephalus *Ceraurus pleurexanthemus Green *Onchometopus simplex Raymond and Narraway Christiania Bed.—This division of the Chambersburg limestone is best developed on the east side of the Martinsburg shale belt in southern Pennsylvania where it reaches a maximum thickness of 270 feet. West of the shale belt it is absent from the section, but going southwestward into Maryland this division reappears and gradually increases in thick- ness until northern Virginia is reached, where it is 40 feet thick. The prevailing rock of this division is thin bedded, shaly limestone and cal- careous shale sometimes quite fossiliferous. The brachiopod Christiania trentonensis is the most characteristic of the described species and speci- mens may usually be found at its outcrops. In Pennsylvania outcrops of the Christiania bed have yielded a fauna of over 40 species which indi- cates that the age of the division is latest Black River or earliest Tren- ton. The list of species, identified by Ulrich, is given below. As this bed is so poorly represented in Maryland only its more characteristic fossils are described in this volume. MARYLAND GEOLOGICAL SURVEY 143 Incomplete Faunal List of the Christiania Bed, Chambersburg Limestone Echinospherites aurantium americanum Bassler, Crinoid plates - Hemiphragma cf. H. irrasum Trematopora cf. primigenia Arthropora bifurcata Ulrich Rhinidictya cf. R. neglecta Orbiculoidea lamellosa Hall Orthis tricenaria Conrad Scenidium cf. 8. anthonense Dinorthis sp. cf. D. subquadrata Strophomena sp. Leptaena cf. L. charlottae Plectambonites sp. Plectambonites pisum Ruedemann Christiania trentonensis Ruedemann Triplesia (Cliftonia) simulatrix Bassler Triplecia cf. T. nucleus Parastrophia hemiplicata Hall Zygospira exigua (Hall) Ctenodonta sp. Lepidocoleus, 2 undet. sp. (near L. jamesi) Illaenus sp. Isotelus gigas Dekay Fragments of Cryptolithus or Tretaspis Greencastle Bed.—The thickest sections of Chambersburg limestone are in southern Pennsylvania in the vicinity of Greencastle, where 200 feet of heavy bedded, impure limestone follow the usual Christiania bed and underlie the base of the Martinsburg shales. Reference to the sec- tions on another page shows that this member can be recognized as far north as Chambersburg, but that it does not appear in any of the sections west of the Martinsburg shale belt. It appears that after the deposition of the rather widely distributed Christiania bed, a local depression in the sea, extending from about the Maryland state line northward to and beyond Chambersburg, allowed the accumulation of this considerable thickness of calcareous sediments before the inauguration of the basal Martinsburg shale. This division, for which the local name Greencastle bed is employed for convenience of reference, is interesting from a paleontological standpoint, first because it contains fossils found also 10 144 Tore CAMBRIAN AND ORDOVICIAN Deposits oF MaryLanp in the underlying Christiania zone and second because the guide fossils of still lower members of the Chambersburg limestone, Nidulites and Echinospherites, here reappear in well developed, apparently typical specimens, The number of species found in this bed is rather large but only two apparently characteristic forms, the cephalopods Orthoceras arcuoliratum and Cyrtoceras camurum, are described in the present volume. SECTIONS OF THE CHAMBERSBURG LiMESTONE.—-Extended outcrops of the Chambersburg limestone are so few in Maryland that in order to get an idea of the formation it is necessary to study the exposures in con- tiguous states. In Maryland there are only two places, namely, at Pines- burg Station and Wilson, where a detailed section of the formation can be studied, but in Pennsylvania there are numerous localities where all the members of the formation can be seen to great advantage. As noted above the formation varies considerably from east. to west and it has been found conyehient to study the divisions in sections exposed east of the Martinsburg shale belt and west of the same area. Throughout the Maryland basin the datum plane for the base of the Chambersburg is the Upper Stones River dove limestone which is every- where developed and easily recognized. The various sections quoted below were prepared by E. O. Ulrich, with whom the writer was associated in the study of this limestone. Most of them have since been published in the Chambersburg-Mercersburg folio. Sections East of Martinsburg Shale Belt in Pennsylvania.—Although the Chambersburg limestone is named from Chambersburg, Pennsyl- vania, its outcrops at this place are too few or incomplete to give a good idea of the entire section. The Christiania and Greencastle beds forming the upper part of the Chambersburg are well exposed here, the Echino- spherites bed: is well shown along the railroad, but the Nidulites bed is mostly covered and the Tetradium cellulosum bed is not seen at all. This section, which is given below, is particularly interesting in showing the development of the Greencastle bed and also in exhibiting the different faunal zones of the lower part of the Martinsburg shale. Maryianp GrotogicaL Survey 145 Section of Martinsburg Shale and Chambersburg Limestone Northwest. Corner of Chambersburg, Pennsylvania Martinsburg shale. Unfossil_ferous black fissile shale............ccceeeeees awaes oe Black shale with Corynoides fauna at base....... Bake baarekareens tae 32 Limy shales with Cryptolithus.........cccccceeccccccceceees 10 Thin blue to black limestone holding the Sinuites fauna at the DESO: ascieies soeis Since aie en ewes seine eed aitigier a ayeten a aateue Ss 10 Chambersburg limestone. Greencastle bed. Massive dark bluish limestone............ ee daceuie OR Shae sare ease 9 Yellowish limy and arenaceous shale with cobbly shaly and sandy l’mestones at base...........cccceeccecceecs arcuate 66 Christiania bed. Shaly limestone with Christiania trentonensis (lower beds of formation not exposed in this section but shown elsewhere iN: VICINITY.) oss ciaswe dae wah bie aa ae Deed 6 Mame Sarai 50-++ Nidulites bed. Compact, massive, dark gray limestone...........0.0.seeeees Echinospherites bed. Argillaceous limestone weathering cobbly.............. saeee Tetradium cellulosum bed. Massive fine grained dark limestone.............ceeeeeee eens toe Stones River limestone. South from Chambersburg along the same general line of outcrop an excellent section is exposed in the railroad cut two miles southwest of Marion. This is the most complete and continuous section of the forma- tion known in the area east of the Martinsburg shale belt. Fossils are not as abundant in some of the beds as they are elsewhere, but the lithologic characters of the different divisions are well developed and the section exposes all of the members recognized east of the shale belt. The Green- castle member, however, is not shown in this particular section’ which ends at the Martinsburg shale on the west, but east of the section along the railroad near the pike, the Sinuites bed of lower Martinsburg shale is underlain by 150 feet of dark gray massive limestone containing the fauna of the Greencastle member. 146 Tur CamBriaAN AND Orbovic1sNn Deposits or MaryLAND Section of Chambersburg Limestone Two Miles Southwest of Marion, Pa. Martinsburg shale. Chambersburg limestone. Greencastle bed. Feet Only residual shale and thin limestone seen. At the top are black carbonaceous limestone and a thin sandstone, capped by a thin, coarsely crystalline limestone bed containing Lingula, representing undoubtedly the Corynoides bed commonly found near the base of the succeeding Martins- burg shale ............. Ase auauadensr aigusutasua temapeuntes ih Ge tebe atadduoisce 150 Christiania bed. Interbedded thin calcareous shale and shaly limestone with a few fossils which indicate the Christiania fauna....... ..- 100 Nidulites bed. Dark, nodular, thin-bedded limestone; fossils rare............ 50 Dark, fine-grained, platy limestone; contains Nidulites and HSSOCALCH: LOSSIS sesicics sctoueg seanetevesd house aun ane e's Mleud.n alee ae 94 Compact, dark-gray, thick-bedded limestone; upper part very fossiliferous, containing numerous cystids and Nidulites.. 108 Echinospherites bed. Dark, argillaceous, cobbly limestone, shaly in lower part; very fossiliferous, containing a layer filled with the ball cystid Echinospherites ..... ge at apt ea Welgis a Seanad oav sar aptece pvecn avast ond . 65 Limestone like overlying bed but even darker in color and interbedded with subcrystalline limestone layers; fossils SCARCE) dows ee sive Oa Re eT ae ia 40 Tetradium cellulosum bed. Grayish to dark, dense thin-bedded limestone, containing Tet- radium cellulosum and Leperditiad........ ccc cc cecseeeeee 150+ Stones River limestone—contact not exposed. ‘ Four miles south of this section the Cumberland Valley Railroad crosses the Chambersburg limestone at Greencastle, Pennsylvania, and exposes the Nidulites, Christiania, and Greencastle beds. This section is of par- ticular interest in showing the extreme development of the Greencastle bed in the railroad cut starting at the bridge just north of the town where about 200 feet mainly of dark blue massive limestone with rather numer- ous fossils intervenes between the typical Christiania bed and the usual strata of the basal Martinsburg shale. The details of this section, as recently determined by Ulrich, are as follows: MARYLAND GEOLOGICAL SURVEY | 74% Section of Upper Divisions of Chambersburg Limestone at Greencastle, Pennsylvania Martinsburg shale. Feet Black fissile shale at top and shaly limestone below, not well OXDPOSCO. 6% snes oH Oe Sita oe Bae Mae elaaie PS WIE Ba LEMS Ee Chambersburg limestone. Greencastle member. Rather massive, dark blue fine grained limestone with gastro- pods and hemispheric bry0zoa........... cc. cece eee eee 40 Argillaceous cobbly limestone, sandy at base..............06- 8 Massive grey to dark blue fine grained fossiliferous limestone. Nidulites abundant at base......... cece cee ee ee eens 50 Massive gray to blue subcrystalline limestone................ 12 Dandy “SHALES. sciicesveenes cise evade Gerd gaa e aliens Seselh aw alee 8 Massive granular limestone......... cece cee eee eect ee eene 60 Sandy limestone and sandstone.......... ccc eee e eee cee eeee 20 Christiania bed. : Argillaceous thin bedded limestone with Christiania trento- nensis, etc. (exposed at southwest end of bridge)....... Nidulites bed. : Massive grayish limestone with Nidulites fauna. (Underlying strata mot CXPpOSed) ..... cece ccc e eee teen eee cert eee enee This eastern band of outcrop continues into Maryland, but disappears by faulting about a mile south of Cearfoss. The exposures of the Cham- bersburg in this part of Maryland are extremely poor, but the formation can be clearly recognized by the cobbly appearance of the weathered rock. No section could be made in this part of the state, nor were the rocks well enough exposed in the southern part in the big bend of the Potomac River where the formation outcrops again. Sections West of Martinsburg Shale Belt in Pennsylvania.—In south- ernmost Pennsylvania numerous belts of Chambersburg limestone are brought to the surface by the geologic structure which causes the great cove in North Mountain in which Mercersburg is situated. This low- land area affords numerous sections of the limestone and many excellently preserved fossils have been collected. ‘These sections are par- ticularly interesting because they contain beneath the Tetradium cellulo-, sum bed, which forms the base of the Chambersburg in the eastern lines, of outcrop, a subcrystalline, massive limestone reaching 100+feet in, thickness, characterized by a fauna which is related to both Chazyan.and, Black River faunas. Another interesting feature is that the Christiania. 148 Tue CaMBRIAN AND OrbOvICIAN Deposits oF MaryLAND bed which is so well developed east of the Martinsburg shale area is here entirely wanting, the Nidulites bed of the general section being succeeded immediately by the Martinsburg shale. The easternmost belt of outcrop in this western area affords the following section which is exposed south of St. Thomas. This section as described by Ulrich is interesting because it is in the most easternly belt of the trough in which the Caryocystites bed is developed. The next outcrop of the Chambersburg limestone to the east contains no representation of the 110 or more feet of the Caryocystites bed as here developed. Section of Chambersburg Limestone 24% Miles South of St. Thomas Martinsburg shale. Typical dark shale. Feet Thin calcareous shale, underlain by calcareous black shale and hard thin black limestone with the Corynoides fauna at top. 31 Coarse granular fossiliferous limestone (Sinuites fauna)...... 7 Chambersburg limestone. Nidulites bed. Black cobbly thin-bedded fossiliferous limestone................ 53 Tetradium cellulosum bed. Massive granular or finely conglomeratic gray, highly fossili- ferous limestone (Beatricea numerous).............-2000- 15 Subcrystalline, very fossiliferous gray limestone (Leperditia numerous) .......... Sea ete os are £8 aie RA aa es MESS eS 1 Granocrystalline unfossiliferous gray limestone, in part minutely CONBIOMEPAUE -wiis ev sic se see areies Sees wee ee Meee we as 18 Caryocystites bed. Bluish subcrystalline limestone containing numerous Caryocys- tites plates and Solenopora COMPACIA........ ce eee cence cee q Cobbly dark subcrystalline limestone, more massive in upper DTG shia seeks V ave ants: Fie ala erenerahale etvergnave Mare vas eit altgsin later shale Sub heeaiientay 9 ae 105 Stones River limestone. Fine even-grained pure limestone, drab to dark gray, thin bedded above, less pure DelOW... 2... cece cee ee ewe tere eee eneeees The railroad cut just north of Dickey’s station, four or five miles south- east. from Ft. Loudon, exposes a good section of the formation, particu- larly of the middle beds. The Echinospherites bed was not distinguished, but it is possible that it may be included in the cobbly limestone at the base of the Nidulites bed. As usual in these western bands of outcrop, the Christiania bed is missing. MARYLAND GroLocicaL SuRVEY 149 Section of Chambersburg Limestone One-Half Mile Northwest of Dickey, Pa. Martinsburg shale. Feet Fissile shale, limy at base...... 0.0... ccc cece cece eee eee enees Thick bed of dark-gray coarse crystalline crinoidal limestone, fossiliferous (Sinuites bed) ............ccece eee eeaees 6 Chambersburg limestone. Nidulites bed. Thin-bedded cobbly, dark, fine-grained limestone containing Diplotrypa appalachia, Plectambonites cf. P. sericeus, Leptaena sp., Pianodema cf. P. subaequata ............... 37 Rather massive gray to dove-colored fine-grained mottled lime- stone banded in part........ ccc cece ccc e eee reese cence 18 Fine-grained platy to cobbly gray limestone with few Diplo- CRY DG i585 st sw TR RG REBT Rees RE NG Se Ava co cub a8 Bode Ba we 30 Tetradium cellulosum bed. Massive fine-grained dark limestone containing Beatricea and Tetradium CelluUlosum ....ci cece ccc cence cece cncececeuce 34 Caryocystites bed. Dark compact subgranular to crystalline limestone, with Caryocystites plates ...... ccc ccc ccc eee tee eect eeee 8 Concealed, 170+ feet, of which probably at least 130 feet belongs to the Chambersburg.............ccecceeceeeeee 130+ Stones River limestone. Thin bedded pure fine even-grained drab limestone............ 257+ The railroad cut just south of Fort Loudon exposes the Tetradium cellulosum bed to advantage and here good fossils from this zone can be had. Faulting has somewhat confused this section, but the locality is of particular interest in showing an unconformable contact between the Caryocystites and the overlying Tetradium cellulosum beds. The lowest six inches of the latter consist of compact clayey limestone filling irregu- larities in the surface of the underlying bed. Evidence of a time interval is also shown by the parasitic bryozoans and the expanded bases of Cleioceinus which are attached to the eroded surface of the underlying bed. 150 Tur CaMBRIAN AND ORDOVICIAN Deposits or MARYLAND Section of Chambersburg Limestone One-Half Mile South of Fort Loudon, Pa. Martinsburg shale. Feet Fissile shale with thin, hard, dark calcareous beds on fresh ex- posure, 100 + feet, underlain by 40 feet of hard calcareous dark shale and thin limestones, weathering light gray, with graptolites at top. gy Sinuites bed. ‘ Subgranular black crinoidal limestone containing Sinwites and TYINUCIOUS: 6c cewece ness eowes 4 Shoe wantaucena jens Sia esse ea Ss 2 Chambersburg limestone. Nidulites bed. Dark fine-grained limestone weathering cobbly...... ake coapatevace 36 Echinospherites bed. Rather dark thin bedded and shaly limestone with fossils, among them fragments of Hchinospherites..........0005 15 Massive dark subgranular limestone.............ce cece recess 12 Tetradium cellulosum bed. Pure dove-covered fine even-grained limestone, containing Tetradium cellulosum and Leperditia in fine conglomerate. 8 Pure granular and subodlitic limestone, upper beds coarsely granular; contains Leperditia and other ostracoda........ 9 Irregularly bedded compact clayey limestone filling irregulari- ties in top surface of underlying bed. Contains Helicotoma planulatoides, Beatricea and other fossils............... 1 Caryocystites bed. ° Heavy-bedded gray granular to subcrystalline limestone; very fossiliferous; trilobites, brachiopods, Caryocystites plates, and Solenopora....... Wb 84 Pas T a TES ee ee 10 Dark-blue flaggy limestone, few fossils............-e ee ee ees 8 Poorly exposed dark granular limestone, estimated........... 100+ Stones River limestone. Pure dove-colored limestone with Leperditia........... eae ee 200-++ An excellent section showing the three divisions usually developed in this area is exposed on the banks of the west branch of Conococheague Creek two and one-half miles southeast of Mercersburg, just south of the Greencastle turnpike. In this section the Sinuites zone marking the base of the overlying Martinsburg shale is very fossiliferous and easily recog- nized. The fine-grained, pure limestone of the Stones River also clearly marks the base of the formation. MaryYLAND GEOLOGICAL SURVEY 151 Section of Chambersburg Limestone on West Branch of Conococheague Creek, 2%: Miles Southeast of Mercersburg, Pennsylvanta Martinsburg shale. Feet Fissile shale, overlying calcareous black shale and hard thin black carbonaceous limestone, containing graptolites and TANGUIG: 6161 ‘HOIMIA O FAT ‘AHdAVUNOADOATVd NVOIWANV HLYON 156 Tur CAMBRIAN AND ORDOVICIAN Deposits oF MaryLAND miles wide just west of Williamsport. In its course through Maryland, Conococheague Creek is confined to this belt of Martinsburg shale, and the rugged topography caused by its erosion affords many outcrops of the strata. Exceptionally fine exposures occur, however, along the Western Maryland Railway from Williamsport west to Pinesburg Station. The underlying shale rock is shown almost continuously between these two places. Perhaps nowhere else in the Appalachian Valley is there such a continuous section of this formation exposed with all its attendant fold- ing and faulting, and these railroad cuts will long remain classic ground for the study of this great syncline. This section clearly brings out two well-marked divisions in the forma- tion, the lower part consisting of a thick mass of black shale, and the upper portion for the most part of yellowish-green sandy strata. These two portions are distinct enough in the Massanutten syncline to be mapped as separate divisions, but in the North Mountain uplift to the west they grade into each other so gradually that it is impossible to map them separately. Sufficient fossil evidence has been found in Maryland, but especially in southern Pennsylvania, to show that these two lithologie divisions corre- spond to definite portions of the general time scale. The lower black shale division contains, near the base, several horizons with faunas of Trenton age. It is probable, although not yet established by paleon- tologic evidence, that the upper part of these black shales corresponds to the Utica shale of the New York section. In the area west of the Massa- nutten syncline the sandy division has furnished numerous fairly well preserved fossils of Eden age. In the North Mountain uplift this sandy Eden division is followed by gray sandstones with a maximum thickness — of 450 feet in which a considerable number of Cincinnatian (Lower Mays- ville) fossils has been found. These gray sandstones are still included in the Martinsburg shale, but the overlying soft red sandstone and red shale are so distinct that they have been separated as the Juniata formation. The Martinsburg shale as here developed, therefore, ranges in age from the Lower Trenton to at least the Lower Maysville and comprises portions of the Mohawkian and Cincinnatian series. MARYLAND GEOLOGICAL SURVEY 157 LirHotocic CHaRacTERs AND SxEctTions.—As just noted above, the Martinsburg shale consists in general of black shale forming the lower division and light-colored sandy shales the upper, but its lowest beds are of thin-bedded limestone and calcareous shale, while the uppermost beds are gray sandstone. The formation thus includes a variety of rock types, but shale is the predominating rock, so that the lithologic designation “shale” for the formation as a whole is appropriate. Depending more particularly on fossil evidence, four distinct divisions can be recognized in this shale, although all may not be present in the same section. These divisions with their approximate. thicknesses are expressed in the fol- lowing general section : General Section of the Martinsburg Shale in Southern Pennsylvania and Maryland Juniata Formation of Earliest Silurian or Highest Ordovician Age. Martinsburg shale. Upper Maysville division. Feet Unfossiliferous sandstone (Oswego sandstone). (Probably represented under cover west of North Mountain, in Mary- and): ss de¥ avaasteonameaed amlee aaeite ds ges eae od SRG Oe Me 150 Lower Maysville division. Fossiliferous gray sandstone with Orthorhynchula linneyi bed at top. (Probably present west of North Mountain under COVER) aac scars oem aees Oe aaeae btiele pusy Groneeien Gee 300 Eden division. Yellow shale and calcareous sandstone interbedded, with upper Hen LOSST1 8" joeee's ogres visa die cused ates GRY Same gee Ne eke 5002- Soft greenish to yellow shaly sandstones and shale with Eden fossils not uncommon at several horizons................ 500+ Trenton and ? Utica division. Dark-gray unfossiliferous shale breaking up into “shoe peg” fragments and often weathering into soft whitish clay... 500+ Black carbonaceous fissile unfossiliferous shale.............. 500+ Caleareous dark shale and thin limestone weathering gray containing graptolites (Corynoides fauna)............ . -20-100 Granocrystalline fossiliferous limestone and shale holding the BSIMUITES PANNA: sis pov isie a ceciens se eats 8 Ha RS Sethe BS ReES OAS He 2-10 Chambersburg LIMeStOme «sinc cig cae tease © eee ba ies wise oe a deena 158 Tuer CAMBRIAN AND ORDOVICIAN DeEposirs oF MaryLAND Although the above section applies in general to all of the Martinsburg shale areas in Maryland and adjoining states, a conspicuous exception to the development of the Eden division is to be noted in the Massanutten syncline area. Here the lower part is the usual thick mass of black carbonaceous shale with the Sinuites bed at the base and the Corynoides bed higher, but the upper portion consists of yellowish-green speckled sandstone so easily recognized that it has been mapped as a separate member. On fresh exposure this rock is found to be a greenish-gray arkose of feldspar and sand with the speckled appearance due to the weathering of the feldspar into kaolin. Small streams draining into Conococheague Creek have cut very rugged picturesque ravines in these strata. , The black carbonaceous shale becomes quite calcareous at the base and appears to grade into the underlying Chambersburg limestone. How- ever, a distinct line of unconformity separates the two formations as evidenced by the varying age of the topmost bed of the Chambersburg in different parts of the valley. Fossils are sometimes abundant in these basal calcareous beds of the shale and the frequent occurrence of the gastropod Sinuites gives its name to the bed. A fauna of almost 50 species has been recognized in the Sinuites bed of Pennsylvania and Virginia, but in Maryland the bed, although recognized, has yielded few fossils. Thirty or more feet above the base of the shale a second faunal zone ig encountered. Here the small comma-shaped graptolite Corynotdes is so abundant that it forms a convenient designation for the bed. This Cory- noides bed has been recognized in several places in Maryland particularly at Williamsport and at Pinesburg Station on the east and west sides respectively of the Massanutten syncline. This fauna is small in num- bers, but it constitutes an interesting horizon throughout this part of the Appalachians. Following the Corynoides bed are the typical black carbonaceous and dark gray unfossiliferous shales of the lower Martinsburg which are so readily recognized on surface outcrops by the “shoe peg ” fragments left “(Nadq) NVLLVNNIONIO— GZ ‘DI *(VOILA) NVILVNNIONIO ATUVA—'fZ ‘DLT 6161 HOININ OF ‘a Q uae Sy, 6161 ‘HOININ OF Ad 7 ie = ‘AHdVYDOIOOA Vd parame \ ee ‘AHdVUDOADOT TV NVOIMANV HLYON : OE, oy NVOIMANV HLYON eee, ST oS ‘ = < Bao) ( ae ‘ ee Me ae ce i ‘ 11 160 Tue CAMBRIAN AND ORDOVICIAN Deposits oF MARYLAND by weathering. In fresh exposures these beds are hard and sometimes reach several feet in thickness, but weathering brings out the intense squeezing and folding to which they have been subjected. Slaty cleavage usually obscures the original bedding, but occasionally ‘a weathered sur- face clearly shows the relation between cleavage and stratification. The rock breaks down into small fragments not unlike shoe pegs and finally weathers into soft whitish clay. With the introduction of sandy sedi- ments in the Martinsburg shale, fossils again are encountered and give a clew as to the age relations. At least three distinct fossiliferous zones have been discovered in these upper sandy shales. Two of these contain numerous species characterizing the Eden division of the Cincinnatian, whereas the third zone shows fossils of Lower Maysville age. As noted before, these fossiliferous zones are encountered only in areas west of the Massanutten syncline as the conditions for the preservation of organic remains were not favorable during the deposition of the sandy strata in the syncline itself. Because of the lack of good exposures of the upper Martinsburg in the mountainous areas of western Maryland, it has not been possible to pre- pare detailed sections showing the position of the fossiliferous beds accurately. In southern Pennsylvania, however, especially in the vicinity of McConnellsburg and Fort Loudon, there are several extensive exposures of these beds. In the Eden portion of the Martinsburg shale 42 species have been recognized. The interval between the top of the formation and the highest zone in which Eden fossils were found is occupied by gray sandstone about 450 feet thick. This is locally divisible into two unequal parts, the lower 300 feet thick, the upper 150 feet, by a fossiliferous stratum in which the brachiopod Orthorhynchula linneyi is a common fossil. Elsewhere in the Appalachian Valley and in the Ohio Valley this Orthorhynchula bed lies near the top of the Lower Maysville. This fossil zone has yielded a fauna of 18 species in southern Pennsylvania, all of which are characteristic Lower Maysville fossils. The overlying unfossiliferous gray sandstone MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXI | Fic. I1.—VIEW IN THE TABLER QUARRY JUST SOUTH OF FREDERICK, MARYLAND, SHOWING THE MASSIVE BEEKMANTOWN LIMESTONE OVERLAID BY THE THIN-BEDDED FREDERICK LIMESTONE WITH A DISTINCT LINE OF UNCONFORMITY SEPARATING THEM. Fic. 2.—FOLD IN SANDY UPPER (EDEN ) PORTION OF MARTINSBURG SHALE ALONG WESTERN MARYLAND RAILWAY, THREE-FOURTHS MILE WEST OF WILLIAMSPORT, MARYLAND, MARYLAND GEOLOGICAL SURVEY 161 bringing Martinsburg shale deposition to a close is equivalent on strati- graphic grounds to the Oswego sandstone of New York, and like it, is apparently either of continental origin or its formation is connected with some phase of sea withdrawal. It is fairly well agreed upon by geologists that the Juniata shales or Red Medina immediately following the Oswego sandstone, is a continental expression of the marine Richmond group of the Ohio Valley. Indeed the two formations have actually been traced into each other. The underlying fossiliferous Upper Maysville (Mc- Millan) formation of the Ohio Valley, which occurs between the Richmond above and the Orthorhynchula bed at or near the top of the Lower Maysville (Fairview) below, is thus almost certainly the equivalent of the un- fossiliferous Oswego sandstone which has the same boundary planes. This correlation is further indicated by the fact that in both instances the Lower Maysville strata pass into the Upper Maysville without any clear evidence of a stratigraphic break. ToPpoGRAPHIC FEATURES AND AREAL DistripuTion.—The largest area of Martinsburg shale in Maryland forms a low plateau averaging two and one-half miles in width. This crosses the state in a belt trending southwest-northeast through the central part of the Appalachian Valley. These shales resist weathering much more effectively than the subjacent limestones, the result being the low, yet topographically conspicuous plateau already mentioned. Although it is much dissected by Conoco- cheague Creek and its tributaries, the upland part of this plateau has an altitude of about 580 feet at the Mason-Dixon line, but descends to about 540 feet at the Potomac River. These upland areas are remnants of an- old peneplain that is still well preserved in the vicinity of Harrisburg, Pennsylvania, and after which it has been named. The excellent and almost continuous exposures of the Massanutten syncline belt of Martins- burg shale along the Western Maryland Railway between Williamsport and Pinesburg Station have been mentioned before. In the limestone valley west of the Massanutten syncline a narrow strip of this shale has been brought down to the surface by faulting. The only “(NVTUWo W-ODTASO) NVILVNNIONIO—')Z% “DIZ ‘(MMIAMIVI) NVILVNNIONIO—'9Z ‘DIWT 6161 ‘HOINTN “OA Nd ‘AHdVUOOIDOA TVd NVOIYVANV HLYON ‘ x \ Ne: ‘ Ne Ss. Se we aN a 6161 ‘HOININ ‘0 A A oe” \ jee ! Rela | "‘AHdVUDOINOA TV <>, NVOIWINV HLYUON poor cme o? MaRYLAND GEOLOGICAL SURVEY 163 other areas in Maryland are in the North Mountain uplift, one forming the eastern slope of Powell Mountain, a second occupying Blair Valley between Rickard and Sword Mountains, and the third and smallest being the Punchbowl area of Bear Pond Mountain. These North Mountain areas show few outcrops of rock and are generally covered by debris of the sandstone formations which form the tops of the adjacent mountains. Faunas.—Although fossils must be considered as quite rare in the Martinsburg shale, sufficient paleontologic evidence has been found to show that faunas of Trenton, Eden, and Maysville age are represented. Two zones with Trenton fossils occur near the base of the formation, the Eden fauna is found in the upper sandy portion, and the topmost sand- stones hold Maysville species. + Fauna of the Basal Martinsburg Shale (Sinuites Bed of Trenton Age.) The most prolific zone for fossils in the Martinsburg shale is a thin band of limestone near the base of the formation which locally is crowded with organic remains. This zone has been recognized at numerous places in southern Pennsylvania, Maryland, and Virginia, although exposures of it are less frequent in Maryland and its contained fossils here are quite few in comparison with the other two states. In southern Pennsylvania the 35 species described in the following pages have been found repre- sented by fairly good specimens, while an additional dozen or more forms are known from poorly preserved fragments. A still larger fauna occurs in this bed at Strasburg, Virginia, where excellent exposures for collect- ing oceurred in the past. The most striking and common fossil of this zone is the gastropod Sinuites cancellatus which has given rise to the name of the Sinuites bed. In the Chambersburg-Mercersburg folio of the U. 8. Geological Survey, this zone has been considered as a transition bed between the Black River and Trenton and placed at the top of the Chambersburg limestone. As indicated later by Ulrich in his Revision of the Paleozoic Systems, the early Trenton aspect of its fauna is more marked than that of the Black River, and the reference of the bed to the basal Martinsburg is believed to 164 Tur CAMBRIAN AND ORDOVICIAN Deposits oF MaryLAaNnD be more correct. Stratigraphic evidence also shows that the Sinuites bed follows a considerable interruption of deposition, since the thickness of strata between it and the Nidulites bed of the Chambersburg is most variable. The best localities for obtaining collections of the Sinuites fauna are just north of the Mason-Dixon line in southern Pennsylvania. East of the Martinsburg shale belt in this region the following fossils have been found: Fauna of Basal Martinsburg Shale (Sinuites Bed), Chambersburg Quadrangle Lingula riciniformis Hall Leptobolus ovalis n. sp. Conotreta rusti Walcott Strophomena sculpturata n. sp. Dalmanella testudinaria (Dalman) var. Microceras inornatum Hall Sinuites cancellatus Hall Sinuites granistriatus Ulrich Cyclora minuta Hall Cyclora parvula (Hall) Cyclora hoffmani Miller Coleolus iowensis James Conularia trentonensis Hall Orthoceras junceum Hall Trocholites ammonius Conrad Eoharpes ottawaensis (Billings) Cryptolithus tesselatus Green Triarthrus fischeri Billings Triarthrus becki Green Bumastus trentonensis Emmons Proetus latimarginatus Weller Cyphaspis matutina Ruedemann Calymene senaria Conrad West of the shale belt in the Mercersburg quadrangle a larger number of species has been identified in the Sinuites zone, but many of them are identical with those in the more eastern belt of outcrop. MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXII fae Fic. 1.—EXPOSURE OF LOWER PART OF MARTINSBURG SHALE ALONG WESTERN MARYLAND RAILWAY, ABOUT ONE-HALF MILE EAST OF PINESBURG STATION, MARYLAND. THE GENTLE DIP OF THE STRATA AND THE CLEAVAGE AT RIGHT ANGLES ARE WELL SHOWN. 4 4G. 2.—ViEW ACROSS VALLEY OF CONOCOCHEAGUE AND BEEKMANTOWN LIMESTONES, FROM A POINT TWO MILES EAST OF LITTLE GEORGETOWN, WEST VIRGINIA. CONOCOCHEAGUE CHERT STREWS THE FOREGROUND. NORTH MOUNTAIN IN THE DISTANCE CONTAINS THE JUNIATA AND TUSCARORA FORMATIONS. MaAryYLanp GEoLogiIcaL SURVEY 165 Fauna of Sinuites Bed in Mercersburg Quadrangle, Pennsylvania Hindia parva Ulrich Lingula riciniformis Hall Leptobolus ovalis n. sp. Dalmanella testudinaria (Dalman) var. Dalmanellg edsoni n. sp. Christiania lamellosa n. sp. Strophomena sculpturata n. sp. Leptaena tenuistriata Sowerby var. Triplecia (Cliftonia) simulatrixz n. sp. Scenidium ? merope (Billings) Cyrtolitina nitidula (Ulrich) Microceras inornatum (Hall) Sinuites cancellatus (Hall) Sinuites granistriatus (Ulrich) Strophostylus textilis Ulrich and Scofield Cyclora hoffmanni Miller Cyclora minuta Hall Cyclora parvula (Hall) Eccyliomphalus trentonensis (Conrad) Coleolus iowensis James Orthoceras junceum Hall Spyroceras bilineatum (Hall) Cryptolithus tesselatus Green Triarthrus becki Green Illaenus americanus Billings Cyphaspis matutina Ruedemann Amphilichas trentonensis (Conrad) The complete list of identified species in the Sinuites bed with their occurrence in the best localities for collecting in southern Pennsylvania is shown in the table on next page. ‘ Fauna of the Lower Martinsburg Shale (Corynoides Bed of Trenton Age).—Thirty feet or more of unfossiliferous black calcareous shale and thin-bedded limestone overlie the Sinuites bed and are in turn followed by a fossiliferous zone crowded with graptolites and other organisms, some of which have a Utica aspect, although the majority are known in the Tren- ton limestone. The abundant occurrence of the small, peculiar graptolite Corynoides calicularis in this zone occasions its name. A second char- 166 Tur CAMBRIAN AND ORDOVICIAN Deposits of MaryLAND FAUNA OF THE SINUITES BED hambers- 2M SSW. | 9 m., §. St. 3 m. SE. ae Pa. Pee Thomas, Pa. ne Ee. Hindia parva Ulvich......... cece cece ee eee de ve * Lingula riciniformis Hall..............00- * * % ae Leptobolus ovalis n. Sp..... sc cece cere eae * * # % Conotreta rusti Walcott................6-- m2 * is Dalmanella testudinaria (Dalman) var..... * % * Dalmanella edsoni n. 8p........ eee ee ee eee % Christiania lamellosa n. 8p.....-... 0000s a * Strophomena sculpturata n. sp..........-6- * * Leptaena tenuistriata Sowerby var......... * Triplecia (Cliftonia) simulatria u.sp...... ® Scenidium ? merope (Billings)............. % ee Cyrtolitina nitidula (Ulrich).............. “g * % Microceras inornatum (Hall)...........-.. ze * 2 ee Sinwites cancellatus (Hall).. * % % Sinuites granistriatus (Ulrich) .. . ot * % * Strophostylus textilis Ulrich and ‘Scofield. ‘ es * * Cyclora minuta Hall......... 2... cece ee eee * # Cyclora parvula (Hall).. * % Cyclora hoffmanni Miller. * * an “Eecyliomphalus trentonensis (Conrad). ‘ ns % x Coleolus iowensis James.... 0.0.06... 00 eee * # Conularia trentonensis Hall............... eg * ia Orthoceras junceum Hall...........0.0000% * % Spyroceras bilineatum (Hall).............. oe * Trocholites ammonius Conrad.............. * ae Eoharpes ottawaensis (Billings)........... Ea * be se Cryptolithus tesselatus Green.............. * * #* * Triarthrus fischeri Billings................- * - Triarthrus becki Green. 5 * x 5 Tllaenus americanus Billings... me Si % * Bumastus trentonensis Emmons. Seca Bee cosens * % Proetus latimarginatus Weller............. # * os Cyphaspis matutina Ruedemann........... * % Amphilichas trentonensis (Conrad)........ a % Calymene senaria Conrad..............0055 * MaryYLAND GEOLOGICAL SURVEY 167 acteristic fossil is the pod-shaped crustacean Caryocaris silicula, indi- viduals of which are often quite common in the shaly limestones. The Corynoides bed has been recognized in the Appalachian Valley from Pennsylvania south to Virginia. In Maryland the shale outcrops in the vicinity of Williamsport and Pinesburg Station have furnished the few fossils so far discovered in this bed. Fauna of the Corynoides Bed Climacograptus putillus (Hall) Climacograptus spinifer (Ruedemann) Corynoides calicularis Nicholson Leptobolus insignis Hall Schizocrania filosa (Hall) Cyclora minuta Hall Cryptolithus tesselatus Green Triarthrus becki Green Lepidocoleus jamesi (Hall and Whitfield) Caryocaris silicula n. sp. Fossils of the Eden Division, Martinsburg Shale—tThe splendid ex- posures of the lower Cincinnatian shales, later designated the Eden shale, in the vicinity of Cincinnati, Ohio, have afforded a wealth of excellently preserved fossils which have been so widely studied by paleontologists that a large described fauna has resulted. The occurrence of this same fauna, well enough preserved for the accurate recognition of at least 42 species, in the sandy upper portion of the Martinsburg shale of Pennsylvania, Maryland, and Virginia, is one of the interesting discoveries of recent years in Appalachian geology. . Numerous exposures of this sandy upper portion of the Martinsburg shale occur along the Western Maryland Railway between Williamsport and Pinesburg Station, but the conditions of sedimentation in this part of the valley seem to have been unfavorable for life, as no fossils could be found. The northward and southward extensions of this Martinsburg shale belt: likewise have furnished no fossils, but the shale exposures in the mountains to the west exhibit several fossiliferous zones. In Mary- land it happens that no good exposures of the upper Martinsburg occur 168 Tur CAMBRIAN AND ORDOVICIAN Deposits or MaryLAND along the roads crossing the mountains, and here the fauna is known only from sandstone debris along their lower slopes. In southern Pennsyl- vania, on the contrary, good exposures of the fossiliferous strata are found along several turnpikes crossing the mountains. The best fossils have been procured from such outcrops along Jordan Knob, one and a half miles northeast of Fort Loudon, Tuscarora Mountain, two and a half miles southeast of McConnellsburg, and Cowans Gap, five miles northeast of McConnellsburg. Two fossiliferous zones are known in the Eden portion of the Martinsburg shale, one at the top of this portion and the second 400 feet lower. The faunas, listed on next page, show that there is little difference between these two zones. Fossils of the Maysville Sandstone Division, Martinsburg Shale.—As explained on a previous page the unfossiliferous red sandstones and shales immediately overlying the Martinsburg shale have been distinguished and mapped in southern Pennsylvania as the Juniata formation. Upon stratigraphic grounds these red beds are undoubtedly the equivalent of the Lower or Red Medina (Queenston) shales of New York. Litho- logically the rocks are similar and in each area they are underlaid by strata with Cincinnatian (Maysville) fossils and followed by the White Medina (Tuscarora) sandstone. The sandstone underlying the Juniata formation and following the sandy shales of Eden age, although covering the well-defined Middle Cincinnatian (Maysville) division of geological time have not hitherto been separated from the Martinsburg shales in Pennsylvania and Maryland. As their area of occurrence in Maryland is so small and good outcrops are almost wanting, the practice of uniting these strata with the Martinsburg shale is continued in this volume. Exposures along the turnpike crossing Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Pennsylvania, have afforded fairly well-preserved specimens of the species listed below. All of these fossils occur at the top of the lower division of these sandstones in a bed characterized by Orthorhynchula linneyi. This Orthorhynchula bed everywhere marks the dividing line between the Lower Maysville (Fair- MaryLanp GEoLoGiIcaL SURVEY 169 LIST OF FOSSILS IN EDEN PORTION OF MARTINSBURG SHALE Jordan rd Tuscarora F | Ga Koh Pa. Mt. (400 feet rt | low tcp) STORY.” | /RelOne aay) oT | 2? Climacograptus bicornis (Hall) var...... | * * a . Diplograptus vespertinus (Ruedemann)... as * “- . * Cornulites flecwosus (Hall)............... % * * ae 1 Jleterocrinus heterodactylus Hall......... * % * . Merocrinus species undetermined.......... * * * . Hudsonaster clarki n. 8p...-. 06. ee eee ees ed ae * bss Berenicea vesiculosa Ulrich............... Ae % 3: os Bythopora arctipora (Nicholson)......... % te ee . + Hallopora onealli sigillarioides (Nicholson) * ae * * 1 Batostoma jamesi Nicholson.............. % a eo * 1Arthropora cleavelandi (James) .......... Re x * oe + Pholidops cincinnatiensis Hall............ % * % * + Dalmanella multisecta (Meek)............ % a * * * Plectorthis plicatella Hall var............ a we * het 18trophomena hallie (S. A. Miller) ........ ae od * ps 1 Strophomena sinuata James var.......... a ine * oo 1 Rafinesquina squamula (James)........... * as 23 i 2 Plectambonites rugosus (Meek)..........- * * * * 1 Leptaena gibbosa (James)..............0- 2g ne * .- 2 Zygospira modesta (Hall)................ ae * * * ? Ctenodonta obliqua Hall...............4+- * ise a 3 1 Ctenodonta filistriata Ulrich.............. % a an 2Clidophorus planulatus (Conrad)......... ody * ue 1 Byssonychia vera Ulrich...........002006 rr * ey + Lyrodesma conradi Ulrich................ ag * sd 2 Sinuites cancellatus (Hall)............... ah * * ar 2 Sinuites granistriatus ah clive wiiaduaes be * ee nis * Tetranota obsoleta Ulrich. A i ate * % ? Hormotoma gracilis (Hall)... % si Be ed 1 Lophospira (Ruedemannia) lirata. (Ulrich) ae oye 3 * 2 Liospira micula (Hall)............00 ee eee % Ais % Mo 1@Qrthoceras transversum Miller ........... ; a ie * % 1Cryptolithus beliulus (Ulrich)............ % * * * *Cryptolithus recurvus (Uirich) n. sp.. * % % ae 2 Triarthrus becki Green..........0. 000000 * ae 3 -s 1Jsotelus stegops Green..............0.000- S * % % 1Calymene granulosa (Foerste).:..........- * * % *% *Aparchites minutissimus (Hall).......... * es 33 2 Ceratopsis chambersi (Miller)............! * * Be 2Ulrichia bivertex (Ulrich)................ ee * fs * Bythocypris cylindrica (Hall)............ * * * ? Lepidocoleus jamesi (Hall and Whitfield) . * * * 1 Restricted to Eden. 2 Occurs in Ed_n and othet formations. 170 = TrE CAMBRIAN AND ORDOVICIAN Drposrrs or MARYLAND view) and the Upper Maysville (McMillan) divisions, the latter in the Appalachian region being an unfossiliferous, gray sandstone apparently of continental origin and equivalent to the Oswego sandstone of the New York section. List of Maysville Fossils (Orthorhynchula Bed), Southern Pennsylvania Lingula nicklesi n. sp. Plectorthis plicatella Hall Rafinesquina alternata (Emmons) Rafinesquina squamula (James) Orthorhynchula linneyi (James) Zygospira modesta (Hall) Zygospira ? erratica (Hall) Ischyrodonta unionoides (Meek) Pterinea (Caritodens) demissa (Conrad) Byssonychia radiata (Hall) Byssonychia praecursa Ulrich Allonychia ovata Ulrich Modiolopsis modiolaris (Conrad) Modiolodon truncatus (Hall) Orthodesma nasutum (Conrad) Liospira micula (Hall) Orthoceras lamellosum Hall Isotelus megistos Locke THE JUNIATA FORMATION Until quite recently American geologists have been in accord in regard- ing the boundary between the Ordovician and Silurian systems as lying at the base of the Red Medina. Indeed, by many, the base of the Silurian was placed still lower, namely, at the bottom of the Oneida conglomerate which was supposed to underlie the Medina and to be equivalent in age to the Oswego sandstone which actually does occur under the Red Medina. The Oneida conglomerate, however, has been proved to belong at the top of the Medina and may indeed represent the initial deposit of the Clinton. The Oswego sandstone therefore became a valid formation, and the name Oswegan series was coined by Clarke and Schuchert to include the Oswego MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXIII Fic. I.—vIEW oF MARTINSBURG SHALE TOPOGRAPHY, LOOKING NORTHEAST FROM A POINT ONE-HALF MILE SOUTH OF WILSON, MARYLAND. CONOCOCHEAGUE CREEK IS SEEN IN THE FOREGROUND AND THE NATIONAL HIGHWAY IN THE MIDDLE. FIG. 2.—VALLEY OF MARTINSBURG SHALE (BLAIR VALLEY, MARYLAND) VIEWED FROM ROAD, JUST WEST OF UNION BETHEL CHURCH. THE MOUNTAINS ON BOTH SIDES ARE FORMED OF THE JUNIATA AND TUSCARORA FORMATIONS. MARYLAND GEOLOGICAL SURVEY 171 sandstone and the Red and White Medina formations as the earliest major division of the Silurian. The reason for regarding the Oswego sandstone as Ordovician in age has been given on a preceding page. In the standard Ordovician-Silurian section of New York the last fauna of Ordovician age is found in the Pulaski shale where species identical with Lower Maysville fossils of the Cincinnatian section occur. Above the Pulaski shale are unfossiliferous gray sandstones (Oswego sandstone) which in turn are succeeded by the Lower (“ Red”) Medina forming the base of the Silurian, according to the New York geologists. This Lower Medina is unfossiliferous, but in the overlying Upper (“ White”) Medina a fauna of Silurian types is preserved. In Pennsylvania and Maryland practically the same section is de- veloped. The sandstones at the top of the Martinsburg shale contain the Pulaski shale representative with the Lower Maysville fauna and above this a gray unfossiliferous sandstone very similar to the Oswego sand- stone occurs, followed in turn by the typical Red Medina here termed the Juniata formation, and by the White Medina or Tuscarora sandstone. In the extremely fossiliferous Upper Ordovician, Cincinnatian rocks of the Ohio Valley, the equivalent of the Pulaski shale of New York is included in the Lower Maysville, Fairview formation. This is succeeded by the fossiliferous Upper Maysville (McMillan) formation, which in turn is followed by the equally fossiliferous Richmond group. Lately it has been proved by actual tracing that the Richmond group passes laterally into the Lower (Red) Medina of New York. Until the recent researches of Ulrich upon the paleontology and stratigraphic distribution of the Richmond and related formations, the Upper Ordovician age of the Rich- mond fauna had been taken for granted. In his paper on the Ordovician- Silurian boundary, published in the Proceedings of the Twelfth Session of the International Geological Congress, Ulrich has reviewed the faunal and physical aspects of the data rclating to the age of the Richmond group and concludes that the choice of the Medina including the Queenston- Richmond formations by the New York geologists as the base of the 172. Tue CAMBRIAN AND ORDOVICIAN Devosirs or MAaryLAND Silurian has strong evidence in its favor. The present writer has had the opportunity of studying the Richmond group over a large portion of the United States with the result that in previous publications he has classi- fied it at the base of the Silurian. His treatement of the equivalent Juniata formation in this volume under the Ordovician is not due to a change of view, but to the fact that in the Silurian volume of the Mary- land Geological Survey the base of the Silurian is placed at the Tuscarora sandstone. As the Juniata is unfossiliferous and, moreover, is very poorly exposed in Maryland, further details are believed unnecessary here, and the reader is referred to the publication by Ulrich cited above for more data as to its age. In Pennsylvania and Maryland the red sandstone and shales of the Juniata formation form the upper slope of the mountains just west of the Great Valley. These mountain slopes usually show only reddish sand- stone blocks and it is only in cliffs or in road sections that the interbedded red shales can be seen. The sandstone frequently shows cross bedding and sometimes conglomerate beds of white quartz or red jasper boulders or occasionally red shale pebbles are developed. The occurrences of the formation in Maryland consists of small areas on Bear Pond Mountain, a narrow strip on Fairview Mountain and another narrow strip along the eastern side of Sword Mountain. None of these areas shows a section of the rocks and the red shales and sandstones are known only from surface debris. The relations and general characters of the Juniata and associated formations are well shown in the following generalized section of Upper Ordovician and Early Silurian strata made by E. O. Ulrich and the writer. This section is exposed along the west slope of Tuscarora Moun- tain between McConnellsburg, Pennsylvania, and the summit of the mountain, along the Mercersburg pike starting about a mile and a half southeast of McConnellsburg and continuing southeast and south for about two and one-half miles. MARYLAND GEOLOGICAL SURVEY 173 Section Along West Slope of Tuscarora Mountain, Southeast of McConnellsburg, Pennsylvania Silurian—Tuscarora sandstone. Feet Massive granular white quartz sandstone.............. eee eeees 200-4- Ordovician or Silurian—Juniata formation. Soft red unfossiliferous sandstone and red shale, interbedded..... 400+ Ordovician-Martinsburg shale. Oswego gray sandstone member.......... ce. cece e eee eee eeeees 150 Maysville (Fairview) fossiliferous gray sandstone (Orthorhynchula bed at top) vvccrinessaicadnearnidaason essed eeawes es Baw ewes 300 Upper Eden shale and calcareous sandstone interbedded.......... 400 Middle Eden fossiliferous shale weathering yellow............... Lower Eden shales, not exposed.......... 2c. eee cece eee eens Trenton and Utica ? black fissile unfossiliferous shale with black shale at base bearing graptolites ............. 2. cs cee eens Chambersburg limestone 1%4 THe CAMBRIAN AND ORDOVICIAN Deposits or MARYLAND | ORDO- CAMBRIAN mee WavucoBaNn OZARKIAN CANADIAN | Aca- dian | Note: 1=Stonehenge Member 2=Cryptozoon steeli Bed 8—=Ceratopea Bed 4=Turritoma Bed =Greencastle Bed 6=Caryocystites Bed 7=Tetradium Bed 8=Echinospherites Bed 9=Nidulites Bed 10=Christiania Bed 11=Eden Division 12=Sinuites Bed 13=Corynoides Bed 14=Fairview Division Conococheague Limestone Antietam Sandstone Tomstown Limestone | Elbrook Limestone Beekmantown Limestone | Harpers Shale I { Waynesboro Form Chambersburg Quad. Chambersburg Quad. Eakles Mills Near Smithsburg | Near Waynesboro, Pa. Williamsport :___| Near Charlton New Mexico | Near Hagerstown { Near Funkstown Smithsburg Huyett UW. side Blue Ridge | Little Antietam Cr. | Near Waynesboro, Pa. | Near Waynesboro, Pa. | Sharpsburg | Near Antietam Station | Near Funkstown | Chambersburg Quad. |New York | Virginia |'W. side Blue Ridge | Utah [Eakles Mills | Eakles Mills | Colorado THALLOPHYTA, Algae Cryptozoon proliferum Hall ........cccceeeeeeuee! sual salle [esate [alle Cryptozoon undulatum Bassler n. i Cryptozoon steeli Seely .... ce. cece eee Paleophycus tubulare Hall ....... weve we ‘ sels Solenopora compacta (Billings) ........... Saad oe a fs a Nidulites pyriformis Bassler ..........4. estes ial el cca Receptaculites occidentalis Salter SPECIES | | * * * OF * NOMA WH PoriIFERA. Spongiae Rhabdaria fragilis (Billings) Camarocladia rugosa Ulrich Hindia parva Ulrich ............... wo hoH CoELENTERATA. Anthozoa Columnaria (?) hallt Nicholson ....... Streptelasma profundum (Conrad) Tetradium ? simplex Bassler n. sp.... Tetradium syringoporoides Ulrich Tetradium columnare (Hall) ....... wee eefeefe Tetradium cellulosum (Hall) ........ce eee e cease wealeiate talline 2: OomLrwrr CoELENTERATA. Pe Climacograptus putillus (Hall) ..... Climacograptus spinifer (Ruedemann) * Peer | Climacograptus bicornis (Hall) ........ wee de elespeedee a: i Diplograptus vespertinus (Ruedemann). Corynoides calicularis Nicholson .......... He HOO wA~I ECHINODERMATA. Cystoidea Echinosphaerites aurantium americanum Bassler n, var,||-+|+-J--je0 eejecjeefeclee cel feel eel clon ee ce eefeeleele effi leefeelate CORVOCYSECTES® ABP s5 ts stein AS tana Asana se es aomraete wiaronanserena te sara Pah bee | eae | en eee ae a) Ua Sale eo EcHINODERMATA. Crinoidea ! : | | Reteocrinus ? sp... Carabocrinus sp - Heterocrinus heterodactylus Hall ...... MerOCTINUS SP ite aoe ain eie id ae eeicee tailed gs evoots lal fe.cpavel aiff erry ace eval so) isl aval led ECHINODERMATA. Stelleroidea | Hudsonaster clarki Bassler n. sp..... sisvanae 4 Resparius MoLuuscoIpEA. Bryozoa Corynotrypa inflata (Hall) ............ee eee Corynotrypa delicatula_(James) Berenicea vesiculosa Ulrich .... Orbignyella wetherbyi (Ulrich) Prasopora insularis Ulrich ..... Prasopora contigua Ulrich ...... Dianulites petropolitanus Dybowski Hemiphragma irrasum (Ulrich) ........ceeeeeeuee . Diplotrypa ? appalachia Bassler n. sp....... Batostoma jamest Nicholson .......-..++.00- Bythopora arctipora (Nicholson) ...... llopora onealli. sigillaroides (Nicholson) ” 13] Escharopora confluens Ulrich ..........45 we Qo oo ~ H SCOONAMTAWHYH Be Noe 175 MARYLAND GEOLOGICAL SURVEY ORDOVICIAN NNATIAN MOHAWKIAN AND CINCI AN CHazy. i CANADIAN Martinsburg Shale epeuey | ejosouuryy | UISUODSI AK | Linosstyq | sassouuay, | _ Ayonquayy | _ OFYO | _ vruysara | YIOX MON | __ “peng Singsiaquivy, | ri podsureritAy | aI MOLE | =< FW pavyory | Ayun0g u0zBurysv Ay | ‘pend Bingsssosa7y | or IB [este ela: eo] el oe Lynn] 11 11)..|.- Ohambersburg Limestone auoysaully JaATY su0}g auoysautyT uMOJURUTYIag Bismy ‘eruoyys| | eptury | vyosouur yy | ursuoost M | BMoy | aassauuay, | ~Ayonguey | _ oo | | BIUTSITA | BIULSITA 489A, YOK MAN Aaslae MAN “peng sinqsssd19]4 _ ‘peng Simqsiaqureyo ! wos | Uorye}g singqsaurg | OK MON | epeurg ‘pend dinqsiaqueyo OTITASULSNV_ Ivan UOSTIAL Leuopsewry yoreperg | Uuolzeyg Sinqseurg Yolepaig jo yseq BIUIBITA Aasiae MAN YOK MON quowse A | “Bpeueg | “pend sinqsiadieaqy | 176 Tue CAMBRIAN AND ORDOVICIAN Deposits oF MARYLAND ORDO- , CAMBRIAN VICIAN ice Wavconan 8 5 OzaRKIAN CANADIAN g Ee | te Note: 8 3 E 5 1=Stonehenge Member G = | doje 2=Cryptozoon steeli Bed 2 g = |els s 3=Ceratopea Bed 3 a |of.E|| Conococheague Ze 4=Turritoma Bed a se |i Limestone Bs 5=Greencastle Bed p E Ealied ‘ 8% 6=Caryocystites Bed @ 3 2 é g Ee 7=Tetradium Bed e 3 EB las $35 8=Echinospherites Bed a mi é& |tla a 9=Nidulites Bed 10=Christiania Bed Ald. | 11=Eden Division | 4 iS sts 3 : beg 12=Sinuites Bed Y jax |S ee Bl is ‘y 13=Corynoides Bed =] (3S?) (SI lalsists) IS] _8 e ie 14=Fairview Division 3 Fle Ss 58 ss ka EIS E E algae] |Belaelefs| |siSie zisle'8) B® FASS 2) a SIS\4 late Z| 2 SElelsie] |8 Riles S|MSERISIEI SIE | ee la). Z{sl4/s'e| 2 Al l=] |S) 2) Ste 1S) S)8 18/8) 5/251) of Rle|s/ai8) £ als] efs! 21S) 22 EEL Pa 8 me Shc | O42 8 | “le|°3 & Slels|s als/Esle.e clelcle BgEls/58 * * oe Vio! OF vo el ojo | oO SPECIES SF Seaaoezalzalaee Oa e SSletaz ears MoLuiuscoipEa. Bryozoa.—Continued | 14|Arthropora bifurcata Ulrich .......ccceecceweewee| tp fecde cs elects ef asfeale spe cle cfececleefen 15|Arthropora cleavelandi (James) ....... wee eee e wee tte epeclecietles . ei ara lh an 16|Chasmatopora reticulata (Hall) ........ een ewe eeefetfeafe cles cele cle eter afore elie 2 17|Chasmatopora sublaza (Ulrich) ...........4. seeeedecfeedes sft sefeede feet 18|Helopora divaricata Ulrich...... wide ale ecaise ctv a aMecaiecas a ste spesfee cele ele alee oof sefe rte rte 19|Helopora spiniformis (Ulrich) ....... dsseibie ws Boe seseudie ls seleafeale cle cfe spe peefecde ae ape apse i 20|Rhinidictya neglecta Ulrich ..........eeeeeee ewaelfecferfeclestee - i: MoLLuscoIpEA. Brachiopoda. 21 Lingulella BD ced ated of Syecanaiats ates ser tauelicsde Ratoeotee Ato velecdeclecdecfecle Peete cle ad # ‘ safes 22 Leptobolus ? ovalis Bassler n. sp aceyerdsa rere es ney me ese [siduselans iy alates] = ey] . 23|Leptobolus insignis Hall ... wihive. iehdebsjuanevasenelaviys peewee wea Peet fente ee eteele sfeeleele slteeds ecte sla slealsctesimelestooteclestes|eslon 24)Lingula riciniformis Hall ........... win fe tee fee |e eet le Rete se aia [A aie pik] oie nin Salsa la a Saal aow |e | aac 25|Lingula nicklesi Bassler n. sp. 26|Obolella minor (Walcott) .. 27|Orbiculoidea lamellosa (Hall) 28|Conotreta rusti Walcott .. 29|Schizocrania_ filosa (Hall) 30|Pholtdops cincinnatiensis Hall . 31|Eoorthis cf. desmopleura (Meek) | ed aibasa Aree eleG 32|MHebertella borealis (Billings) 33|Hebertella vulgaris Raymond os 34|Hebertella bellarugosa (Conrad) ...........000005 seed B5|Orthis tricendreg Conrad .vsavc+n Gaeaxa dhiawnawes rele Peepectenys sleee fe effe cde ele c}eels ole 36|Plectorthis plicatella Hall .............020005 ewe lieefeepeefe cde cle ele Peele els ele Peele cle eleclecleclesleslecfeePeeleeleeleelecles 87|Plectorthis plicatella Hall var............0.0e0e0s sefeafee 38| Dalmanella testudinaria (Dalman) var... sree eee eadeeledes 39| Dalmanella edsoni Bassler n. sp........-- Ssvaleat sted vellecte epee 40| Dalmanella multisecta (Meek) 41|Dalmanella electra (Billings) 42|Dalmanella_wemplei Cleland ainlsalls e iasslfers [ae sells [ell ace sell ara'|s.9l|svatecs le 43] Dinorthts (Plaesiomys) platys (Billings) .........00jeslecfeefee ecpeeleepe efecto ede Peedecfeclee[eclealeclecleeleeDes 44|Dinorthis pectinella (Emmons) .........e.0cee008 wefeaPeafe ete efeefe fe ole fe off. 4 45|Pianodema subaequata (Conrad) ..........00% issasateall aco ltdcel oss levserece Lie ves] ween ch Scho a cael aoa os eves ee erat a 46| Strophomena stosei Bassler n. SP.....s.eeeeeeee sella lave nel ela ce | reece el eel [sells leaders 3 é 47| Strophomena sculpturata Bassler n. sp........0+-205 cope ope cle cde steals Peete fe alls Pe ole ela cde elects afer 5 48| Strophomena hallie (S. A. Miller) ............000- cel Soe Sse] a23'| alles aie [psathaa vel call svelll ess[-a]lacsll eng | woes 49|Strophomena sinuata James ......... oe aide ye acai erars an ais|s ofa ois esleefospecd|s a] ssl ecafoelas[ox|esllsalaatsn)aatnate se eles |ealeefee|es 50|Plectambonites pisum Ruedemann........ a ela ehsess sal esas 6] evel ral| aca Scand | a0 evalls's [lee eis @ aifece 61|Plectambonites rugosus (Meek).......,.0.seeeeeee ria 52| Christiania trentonensis Ruedemann 53] Christiania lamellosa Bassler n. sp 64|Leptaena charlottae Winchell & Seance 55|Leptaena gibbosa (James) ...... 56| Leptaena tenuistriata Sowerby var... 57| Rafinesquina champlainensis Raymond . beats facilis lsvsilassx fare rol tete face [aid ere ana eve | Seaol acalines [acsiecals aif s 58| Rafinesquina minnesotensis (Winchell) ..........45 svallnvel sca hoes fo laces igzal eile: agg [Htaself a4 || aol ens | a olf aves s4f Soe | atten orf s 59| Rafinesquina minnesotensis inquassa (Sardeson) ....|l../..Jicfeclee{ecle Peele ale alfe fe elects fee[e cle cle cle cle sleep cleslecleclesles 60| Rafinesquina squamula (James)........2.ee008 oie. aveloalespep|ee|os[eclers aldallesfes 61| Rafinesquina alternata (Emmons).............0005 ial ecaloul eal a] raion 17? MarYLAND GEOLOGICAL SURVEY ORDOVICIAN MOHAWKIAN AND CINCINNATIAN epeueg | vyosouUly, UISUODSI M Linosst aassouua Martinsburg Shale Ayonquay | oryo | BIUIBITA | yIoxX MeN “peng sZingssequivyo “peng dingsisd1eW qiodswertit “FA MOTAIIC “FA Plexo Ayunog uo0psZuryse . 113/13 |. - 112)/12|12). Bissny ‘eIu0Ysg | epeury BOSOUULL UISUODSI M @mol aessouuay, AYonquey orgo BIUTSITA BIUIBITA 989M Chambersburg Limestone HIOX MAN Aasiae MeN “peng singsisd1ey] ‘pend sZinqsiequreyo OSTA __woryyg Binqsourd | 2 CHaAzyan CANADIAN au0}saully JaATY S807 “YIOX MON epeuty ‘pend sinqsisquevyp aT[TASUUSNLIY IeaN | suoseMT] Yorepeig | auoyseull'yT UMOJUBUTHVI — uoyE}g Banqsautd youepalg jo ystq | “ ByUTSu A Aasiae MON ao ~ “yiox MON juOULIa A peut ‘peng sinqsis010}¢ 178 Tuer CAMBRIAN AND ORDOVICIAN Deposits or MaryLAND be Bee WON COBNANRWNH 14 15 16 17 19 20 21 22 23 25 26 27 28 30 31 Note: 1=Stonehenge Member 2=Cryptozoon steeli Bed 3=Ceratopea Bed 4=Turritoma Bed 5=Greencastle Bed 6=Caryocystites Bed 7=Tetradium Bed 8=Echinospherites Bed 9=Nidulites Bed , 10=Christiania Bed ; 11=Eden Division : 2=Sinuites Bed 18 =Corynoides Bed 4=Fairview Division SPECIES MouLuscoiEa. Brachiopoda.—Continued Triplecia (Cliftonia) simulatriz Bassler n. sp. Syntrophia lateralis (Whitfield) ......... Scenidiwm anthonense Sardeson.......... WEA tare no's Scenidium ? merope (Billings) ........... Cees ee Parastrophia hemiplicata Hall...........e eee eee Camarotoechia plena (Hall) ..........4 Orthorhynchula linneyi (James) ....... Zygospira recurvirostris (Hall) .......eeeeee VerMES. Tubicola Cornulites flecuosus (Hall) ...........45 Mouuvusca. Pelecypoda Ctenodonta gibberula Salter .......... Ctenodonta filistriata Ulrich ..... sigece Mystateresaesnenh Clidophorus planulatus (Conrad) ....... Ischyrodonta untonotdes (Meek) ......... Byssonychta Mera COMIC): sociace is ioa wacentaciew ae Allonychia ovata Ulrich .............4. * Pterinea (Caritodens) demissa (Conrad) Lyrodesma conradi Ulrich ........... Modtolopsis modiolaris ae Modiolodon truncatus (Hall) Mo.uuusca. Gastropoda Turritoma acrea a Lophospira bicincta (H. Lophospira eae lirata (Ulrich) Maclurites affinis (Billings) .......... Maclurites sordidus (Hall) ........... Maclurites oceanus (Billings) .. Ceratopea keitht Ulrich ........ ce eeeeee Helicotoma planulatoides Ulrich . ‘fe Helicotoma verticalis Ulrich ..... fot Zygospira exigua (Hall) ........cee cece eee eee tees Zygospira modesta (Hall) ...... ccc cee c eee eeeee eves 5 =| xsi [| svar Sill azel cca ea ost Zygospira ? erratica (Hall) ........ eee eeeeeeeee sefecfeneelecle deep efee oofie fe eff Scolithus linearis (Haldemann) ............e0005 Ctenodonta obliqua (Hall) tsb cA ates eS Geter asta selene Byssonychia radiata (Hall) .........0-eeee eee Yh ie Byssonychia praecursa Ulrich ..........0 eevee eeee anai's Orthodesma nasutum (Conrad) sen Abeta akeactis, selec a leaelotacel sen baler vbealasliaute Hormotoma gracilens (Whitfield) ............0.05 aatondie Liospira micula (Hall) .........000--. cee eee pebble Maclurites magnus Lesueur .........cc cece ee eeeee < ORDO- VICIAN 4 Ss OZARKIAN CANADIAN a0 vo a g & e 6 8 2 a & EIs e| = E lets i 3 a || /El| Conococheague Eo a e | Limestone Ss z 5 g eis ay ze) 2 | 2 IEE gE Gi g 6 ato gH x < eB |Fla fa Alla le 8] es] 8 o | 2 ol jol,e! |r Au ANTAa|) je : eg y Se] (3) |Jsleel EE j 3 sl |: ms s |2 me Ele a B 5|5/5 A BIO} Ble 3 oe on) = O| to to 2)8la 213] | s]alg s/si8) Js 2s ofzigie 8) [8 SRE Rees SEeNseale | | eleelea| |e Sel se a SEZ | |e BNE es oles ese EER eR se 4 (eae |eoels Sal 8 SoS E18 Bele || Sie gifal*|s 2 Slely sll a giggle Balsiels al siS/B a2 BE Slals 3|8]S|818)¢ 2/5 -|S\c\o)8 | 8 31 Fle FA) Olale alielaliala|4 0) & | O ala 2 |e a imo Pleurotomaria ? canadensis Billings .............4+ sia sca |p al seal ces |=-3 calf avs focal] sca asa Bevel le atte d: Bs aye fora otal hedge asere'l asa Pleurotomaria ? gregaria Billings............. eee losleafecleatals alenfasloales|tftallesle x 25 Pleurotomaria ? floridensis Cleland.............+- ci oa Hormotoma artemesia (Billings) .............45 acellealeaten Hormotoma gracilis (Hall) .........s.0-00- siareelfeailee one rN PING OD 6 ‘ MARYLAND GEOLOGICAL SURVEY ORDOVICIAN epeurp BZOSIUUL IT UISsuoas! A, Limosstjq Sassouud, 4yonquey | oryo | BIUTSILA | YIOK MAN | ‘peng sinqsisqureyo | ‘pend sinqsiaod1eyq | qrodsurertt A “VAL MOTAICT “WA Pleyry ‘syunog uo0zsuryse A, = BISSNY BIUOyIs a | epeurg BPOSOUULT UISUODST AA BMOT eassauua J, Ayonquay orgo BLULsIT A SLUTSITA 489A, yIOX MAN Aaslae MAN “peng sinqsiediay ‘pend sinqsiequieyo UOSTTM UOT}LIG Binqseulg Martinsburg Shale MOHAWKIAN AND CINCINNATIAN Limestone Chambersburg YIOX MON epeurp UO SOUT] ‘pend singsraquieyqo JATY S9U0IS a[[TASUBSNV]_ IvIaN uosTTM | uolzB1g sdinqsourg | auojsoullyT YoLepaiy | YoLlepeig Jo qseq | _ i —_____ BTUTBITA | Aasiae MAN CHAZzYAN < eu0ysawl'y ytOK MON UMOPUBUTYVAT QuOULIO A epturp “pend sinqsiso.1aj¥ | CANADIAN 180 THE CAMBRIAN AND ORDOVICIAN Deposrrts or MaryLaND 87 60 61 62 63 64 65 66 67 68 69 70 71 72 OU De CAMBRIAN ORDO- VICIAN WaucoBAN Aca- dian OZARKIAN CANADIAN Note: 1=Stonehenge Member 2=Cryptozoon steeli Bed 8=Ceratopea Bed 4=Turritoma Bed 5= Greencastle Bed 6=Caryocystites Bed 7=Tetradium Bed 8=Echinospherites Bed 9=Nidulites Bed 10=Christiania Bed 11=Eden Division 12=Sinuites Bed 13=Corynoides Bed 14=Fairview Division SPECIES | Eakles Mills | Harpers Shale |W. side Blue Ridge Antietam Sandstone Tomstown Limestone | Waynesboro Form | Elbrook Limestone Conococheague Limestone Beekmantown Limestone Eakles Mills W. side Blue Ridge Little Antietam Cr. Smithsburg Chambersburg Quad. Eakles Mills Near Smithsburg | Near Waynesboro, Pa. Mouuusca. Gastropoda. —Continued Raphistoma obtusum Cleland Raphistoma ? columbianum Weller Raphistomina laurentina (Billings) Omospira alexandra (Billings) Bucania sulcatina (Emmons) Tetranota obsoleta Ulrich .... Cyrtolitina nitidula (Ulrich) Sinuites granistriatus (Ulrich) Cyclora minuta Mou.usca. Cameroceras sp...... Orthoceras lamellosum Hall .........eeeeeeeeee Spyroceras bilineatum (Hall) Trocholites internistriatus (Whitfield) ........... Trocholites ammonius Conrad ........... Gonioceras chaziense Ruedemann ... Ooceras kirbyi (Whitfield) Cyrtoceras gracile Cleland .. Cyrtoceras beekmanense Whitfield Cyrtoceras camurum Hall ..... ARTHROPODA. Crustacea Strophostylus fees Ulrich & Scofield ............ teroceras inornatum (Hall) Bina aiatvan ong iain Acne lly wie |sve] sce fecal acevo ans lave selfs of sapere |aielace]|s = loves oles) eaters [oo] eau Sinuites cancellatus (Hall) ...1.......cce scene eee cafe ofe cla sls ele cde fe cle ele elle ede offs cle ale cle eleefecleole ele ope clee[eelecle clon Cyclora parvula (Hall) ...... cee cece eee eee eee ee te ale sl aes Cyclora hoffmanni Miller.............0 2 cee ee cess soi] a Pb.ai| sal avellasafio afoie Hyolithes communis Billings .............0.0000. eee[ ef Fol epee] efe s ISQLECK ELLA “SDistoveite aos Fs tasg WS CED WEST Siete 39 wie jevegdaeesy safe epe cle cfe ete afe ope cleo! Mie oP. oll. fe ele ele efe efecto cle cte spe cjecleeieefea]ee Coleolus towensis JAMES «01... cece cece eee eee n eee wafe Pe cde ele cle cfa ofa ope ete elle af Conularia trentonensis Hall ........eec eee e ese enae sjalias bea selena exe Cyrtocerina mercurius Billings .................. rasleauclealealaeleabes|asles Cyelostomiceras cassinense (Whitfield) ? | reece meee lect ede le cle cleo obo ole Eoharpes ottawaensis (Billings) .......... eons ex ase l ers [erelae| sal] aialfoca elec Cryptolithus bellulus (Ulrich) ...........020e0ee oe icale afeafcca]so[siclccef estar Cryptolithus recurvus (Ulrich) Bassler n. sp. 029: 6 Maca avs fevellare sar sie Beate Cryptolithus tesselatus Green ...........e00- aes llialeg|oolestes|eoliefes aah ede. Ampyx (Lonchodomas) normalis (Billings)........ eKeialaafalica| ss 4are|aades aa cr fliecel ella | Near Waynesboro, Pa. Eccyliopterus disjunctus (Billings) ............ de: alee Sl eaillees ea] gellecs les lex fiecls Eccyliopterus triangulus (Whitfield) ......... 5 ene ll esdles|s alas, oisfors [-s]ee|\« feeds al ielece| nai] gels alae [a aliegs Ophileta complanata Vanuxem ......-..-.202-000- Kifeial's o|ccallee|s elsallars|azallos|ta epaeile-c] srctavs| stalk eles tae s vlec 5|Ophileta levata Vanuxem ........ee cree cece e cece atl sia 91 ssope|s al eeefe Ophileta compacta Salter .......c.seseeeeeee eens wafePesfecfeale ole Eccyliomphalus multiseptarius Cleland ........... wise asia e-s]avntove Eccyliomphalus trentonensis ponent) sueythatisa fe Sas Shale Jas saa ae bee lace | Near Waynesboro, Pa. | Sharosburg | Near Antietam Station | Near Funkstown | Chambersburg Quad. | New York | Virginia [Titah | Colorado | New Mexico Orthoceras primigenium Vanuxeml 6 vases cove ee 6:01] 324 [ovellivef are |aefese ose] 876 Orthoceras arcuoliratum Hall .........0e0ese eevee cesfoiefoaleisleelecteiefes Orthoceras junceum Hall ............. sieielesscdsa eal cates yal eeles| saline Orthoceras transversum Miller ...........eeeeeees asa asa [s aio) avs faa | Near Hagerstown | Near Funkstown ! Williamsport Pe eee Deepest Near Charlton Huyett Chambersburg Quad. aes MARYLAND GEOLOGICAL SURVEY 181 ORDOVICIAN MOHAWKIAN AND CINCINNATIAN ? CHAZYAN | \ CANADIAN Bpeueg | vyosauUlyg | UISUODSI AA. Martinsburg Shale ‘peng dinqsiaquivyD LInossi jy vassouuaL, Ayonqyuey ory | VIULaITA | YOX MAN | “peng § sdinqsisd10e;¢ Hodsweitit A FN MOLAITe Ty VAL prey _Aqunog uorsuyyse ay | BIssny ‘BruoyysT epeury vjoseuUlyT UISUODSI AA BAO] | vassauuay, | Ayonqusyy 140 Limestone BIULSITA BIUIBITA 982A, Chambersburg au0}saul] AAA S9U0}g [_suoyseury yoTapasa | auoysewly : uMOJUBUIyaeg yIOx MAN Aesiae MAN ‘pend singsiaosayy “peng singsisquivyy MOSTEM. | uoye4g dinqseurg | YOK MAN | epeury ‘pend sinqsiaqureyo aTAsucsnvy 1vay UOSTEM _uolyeg Binqseutg WHpeiT jo yseq | “BLUTAIT A | Aasioe Man | YOK MON quouLia A tpeury ‘peng sinqssiad1ay 182 THE CAMBRIAN AND ORDOVICIAN Deposits oF MARYLAND ORDO- | CAMBRIAN VICIAN i .e | Waucosan | gs OzarkiaN CANADIAN \ a | 2 2 il. Note: " 6 s £ 1=Stonehenge Member | % g EE 2=Cryptozoon steeli Bed 1 @ & RLS | 3=Ceratopea Bed | 3 a A o}&|| Conococheague zB e 4=Turritoma Bed az) « |[5/5 Limestone 3 § 5= Greencastle Bed | Z 5 Zz She § B 6=Caryocystites Bed | 2 2 aig 5 EB 7=Tetradium Bed |. Ee 3 B BE oC, 8=Echinospherites Bed I 3 5 & ise 2 9=Nidulites Bed oo es 10=Christiania Bed : | do! le 11=Eden Division | | | : alse is! |. : 12=Sinuites Bed is Bae TS i Sig Tc 13=Corynoides Bed S| is al 2} lwsi sts] Bi |S fs S 14=Fairview Division ro «| a | 5 8 8 Is : EC z g i : be alla 82. slaa 3/3]8] is g|2 ofzaigs| |P Erle aS MSIE EEE MS a5). 2] 8 2/Sie) |B A lA) oS SI SAE SIMs sia loelae zal 2 allele. Zela“PleeP Er elec a ciee spnoms aca sage dalseale BSc Bale eis e3 BPRP RR aOlala4 ello 20 ZF Old alla labs nas id a fee eee ARTHROPODA. Crustacea.—Continued 6|Ampyx (Lonehodomas) halli Billings ..........000 sede 7|Dolichometopus SPp........-. cece ‘ 1 8| Olenellus thompsoni CHa) sie sits oa csisenectnaveie ace wexea vaca 9|Hystricurus conicus (Billings) ......cesseceveeees 10|Goniurus caudatus (Billings) ..........ceceeeeeee 11)Triarthrus fischeri Billings .... sav wias 12|Triarthrus becki Green ....... 13|Isotelus stegops Green ......... sae 14|Isotelus megistos Locke ........ccceeeecececeeee 15|Isotelus gigas DeKay ........... oie G[Tsotelus SPic wc ccccsccececvececces 17| Asaphellus gyracanthus Raymond 18] Hemigyraspis collieana Raymond . 19|Symphysurus converus (Cleland) .......... 20|Onchometopus simplex Raymond & Narraway. 21|Illaenus americanus Billings .............040- 22|Bumastus trentonensts Emmons 23|Saukia stosei Walcott ........... iia 24) Proetus latimarginatus Weller ... wee fes 25|Cyphaspis matutina Ruedemann as 26|Amphilichas trentonensis (Conrad) ....... 27|Acidaspis ulricht Bassler n. sp.......e000 28|Calymene granulosa (Foerste) 29|Calymene senaria (Conrad) ......... 80|Ceraurus pleureranthemus Green . 4 31|Pliomerops salteri (Billings) ........ ay fee 32|Pterygometopus callicephalus (Hall) ...........005 : ArTHRopopa. Branchiopoda 33| Ribeiria ? nuculitiformis Cleland ............. ea fee eefecleeleeteafe ef el ARTHROPODA. Ostracoda | 34|Isochilina gregaria (Whitfield) ..... Sern Stade atin tacts Weil's & stl lons. ae ellos [valley eed [el avellevay va. | sean aie xan nats 35|Isochilina seelyi (Whitfield) ....... wide ie 36|Leperditia fabulites (Conrad) ....... 37|Leperditella tumida (Ulrich) ....... 38| Aparchites minutissimus (Hall) . 89|Drepanella macra Ulrich:........ 40|Macronotella ulrichi Ruedemann 41|Ceratopsis chambersi_ (Miller) 42| Ulrichia bivertex (Ulrich) 43| Bythocypris cylindrica (Hall) ........ 44| Lepidocoleus jamesi- (Hall & Whitfield) MALACOSTRACA 45|Caryocaris silicula Bassler n. sp....... Sibviend eteheranes. 34 183 MARYLAND GEOLOGICAL SURVEY ORDOVICIAN MOHAWKIAN AND CINCINNATIAN Martinsburg © Shale epeury | BIOSOUUL HA | UISUODSI AA | Linosstq | aassouuay, | ‘peng § sinqsiso.1ayq | Ayonquay | oryo | BIUTBILA | . OA MEN | “peng Singsraquivyy | “podsuviitas | A MOTAIIR GT | “WA pavyory | Ayn woysuryseAy | : Bisse, SBTUOY Is ||. es he ee ec iy neha omar eee ee ear tpeurg | vyosouuryy Limestone UISUODSI MA BMOT aassauuay, Ayonquay org BIULBITA BIUIBITA 9S9AA Ohambersburg YIoOX MAN Sasiae MAN ‘pend sinqsiad1ayy ‘pend Sinqsisquieyo UOSTEAL uolye}g siInqsaulg CHAZYAN auoysowl'y JOATY satiogg YOR MON epeueg ‘peng sinqsiaquirvyD OT[TASUBSNVT 1eaNy uosTIM uolzeyg Jinqsautg ? CaNaDIAN | aucjseumpy YoLleperd | 3 ENE eal oh Yyoepelg jo seq BIULSITA au0}SoUl'T Aasial MAN YIoX MAN UMOPUBULYVO quouLia A epeurp “peng dinqsied1ayy SYSTEMATIC PALEONTOLOGY OF THE CAMBRIAN AND ORDOVICIAN DEPOSITS OF MARYLAND BY R. S. BASSLER SYSTEMATIC PALEONTOLOGY CAMBRIAN AND ORDOVICIAN THALLOPHYTA, se .carsaca ere tioe en wins GRIT ee R. 8. Bassier. PORIFHRA: 3.252600 tenders dans eo vanes ata tuawews R. S. BassLer. COHRBENTBRRATA. oidsaceueeg eased daean eaten R. 8. Basser. ECHINODERMATAS acowicd Sys kGleeGalcenen en ae R. S. Bassuer. NEB RALES: onc. gog phate Peaks eee tae eae R. S. BAssier. MOLLUSCOIDEA ......... a aie eri Te ae See dees R. S. Basser. MOLDLUSGA. ova acon sere ees eH eas R. S. Basser. ARTHROPODA: sasoc2uiiw nies thease baeaed aus ...R. S. Basser. THALLOPHYTA CLASS ALGAE Cenus GRYPTOZOON Hall CRYPTOZOON PROLIFERUM Tall * Plate XXVIII, Figs. 1, 2; Plate NNIN, Fig. 1 Cryptozoon proliferum Hall, 1884, 36th Rept. New York State Mus. Nat. Hist., pl. vi. Cryptozoon proliferum Walcott, 1912, Smithsonian Misc. Coll. 57, p. 258, pl. xxxvii, figs. 1-3. Description.—< These bodies are made up of irregular, concentric laminae of greater or less density and of very unequal thickness. The substance between the concentric ‘lines, in well-preserved specimens, is traversed by numerous, minute, irregular canaliculi which branch and anastomose without regularity. The central portions of the masses are usually filled with crystalline, granular, and odlitic material and many specimens show the intrusion of these extraneous and inorganic sub- stances between the concentric laminae. That these are intrusions, and not inclusions, is shown from the fact that they can ba traced to a vertical fissure or break leading to the exterior of the fossil and which allowed the crystalline matter to enter.”—Hall, 1884. As noted under the following species, Cryptozoon proliferum is char- acterized by its growth from a widely expanded, almost flat, series of lamellae into confluent heads of a size varying from four or more inches in diameter at the center of a growth to small, concentric areas an inch or less wide on the edge. *In the specific bibliography throughout this volume only the original and the more important subsequent references are cited. The complete bibli- ography for the Post-Cambrian forms may be consulted in the Bibliographic Index of American Ordovician and Silurian fossils published as Bulletin 92, U. S. National Museum. 190 SYSTEMATIC PALEONTOLOGY Occurrence.—ConococHEAGUE LimEsToNnE.—In Pennsylvania, Mary- land, and Virginia this is a characteristic fossil at the hase of the Conoco- cheague limestone. Specimens may be found at practically all of the normal contacts between the Elbrook and Conococheague limestones. The species is particularly abundant in the viciuity of Sharpsburg, Maryland, and also in a cut of the Norfolk and Western Railroad, one mile south- west of Antietam Station where a reef of these algae is exposed. The original types came from the Ozarkian (Hoyt) limestone of Sara- toga County, New York. Collections.—Maryland Geological Survey, U. 8. National Museum. CRYPTOZOON UNDULATUM 0. sp. Plate NXIX, Figs. 2, 3; Plate XXX Description.—The Conococheague limestone in the Appalachian Valley from Virginia to northeastern Pennsylvania and the corresponding strata in New York State afford a second well-defined species of Cryptozodn which occurs in association with C. proliferum. Comparison of the two species will bring out the essential characters of the present new one. Cryptozoon proliferum grows from a widely expanded almost flat series of lamellae into numerous confluent heads of unequal size. In C. undu- latum the laminae are at first evenly undulating, forming in edge view, a pseudo-columnar structure, the columns averaging 20 mm. in width. A cross-section through this part of the fossil shows these column-like areas to be of equal size and totally unlike the corresponding portion of C. proliferum. Following the undulating zone in C. undulatum the laminae go through a stage in which the distinct lamination disappears. Then, with a new growth, the characteristic undulations of the species reappear. Occurrence.—CoNococHEAGUE LimxstonE. Associated with Crypto- zoon proliferum. The types are from a locality two and one-half miles southeast of Funkstown, Maryland, where examples were humerous. Sharpsburg and. vicinity also show numerous specimens, particularly in the stone fences. This species and C. proliferum have also been found MaryLAND GEOLOGICAL SURVEY 191 in the Conococheague limestone as far north as the Reading area of Pennsylvania. They both occur in the Hoyt limestone near Saratoga Springs, New York. Collections.—Maryland Geological Survey, U. S. National Museum. CRYPTOZOON STEELI Seely Plate XXXIV, Fig. 1 Cryptozoon steeli Seely, 1906, Rept. State Geol. Vermont, vol. v, p. 161, pls. xxxiv, xxxvi, xliii, fig. 1. Description.—The Beekmantown rocks of New York, Vermont, and northward into Canada contain a species of Cryptozoon several inches to a foot in diameter which differs from the other species of the genus in that the organism is usually made up of a single globular or hemispherical mass of lamellae. The successive layers are quite parallel and arranged concentrically even in the largest specimens. These layers are composed of a dense material apparently without definite organic structure. In the Cumberland Valley this particular form of Cryptozoon is apparently restricted to a definite zone in the Lower Beekmantown. As the fossil weathers out in large, silicified masses accompanied by much platy chert, this zone is generally easily recognized. Cryptozoon steeli therefore forms an excellent guide fossil in mapping, as it not only assists in the recognition of the strata, but the chert masses accompanying it indicate the outcrops of this zone. These, if plotted, help to decipher the geological structure. The Cryptozoon steelt zone of chert has been a most valuable aid in determining the structure of the Beekmantown in the Valley west of the Martinsburg shale belt where frequently lack of rock outcrops has caused great difficulty in mapping. Occurrence.—BEEKMANTOWN LimESTONE (Cryptozoon steeli zone). In the Appalachian Valley of Maryland and southern Pennsylvania this is a common fossil about 800 feet above the base of the Beekmantown. Numerous specimens may be found among the residual cherts of this zone at practically every outcrop both east and west of the Martinsburg shale belt of Maryland, particularly in the vicinity of Hagerstown. Collections.—Maryland Geological Survey, U. 8. National Museum. 13 192 SYSTEMATIC PALEONTOLOGY Genus PALAOPHYCUS Hall PALHOPHYCUS TUBULARE Hall Plate XXXI, Fig. 1 Paleophycus tubulare Hall, 1847, Pal. New York, vol. i, p. 7, pl. ii, figs. 1, 2, 4, 5. Description.—Although formerly considered as seaweeds, the fossil remains described under this name, and related so-called genera and species, are of very doubtful origin. The particular form here illustrated is interesting because it occurs in such widely separated areas, although the two formations in which it is found are believed to he of the same age. The specimens as observed on weathered surfaces consist of un- evenly bent or flexuose cylindrical stems sometimes gradually tapering to a point, irregularly branched and often bifurcated. In Maryland, as in New York, these stems when weathered appear as if hollow. The stems and branches are usually much compressed, smooth, and preserve no traces of structure. Occurrence: —BEEKMANTOWN LimEsTonr (Stonehenge member). Sev- eral localities in the vicinity of Hagerstown, Maryland. Tribes Hill Limestone. Amsterdam, Canajoharie, etc., New York. Collection.—U. S. National Museum. Genus SOLENOPORA Dybowski SoLENopora compacta (Billings) Plate XLI, Figs. 1-3 Stromatopora compacta Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, pp. 55, 212. Tetradium peachii Nicholson and Etheridge, 1877, Ann. and Mag. Nat. Hist., 4th ser., vel. xx, p. 166, text figs. d-g. Solenopora spongioides Dybowski, 1877, Die Chaetetiden der ostbaltischen Silur. Formation, p. 124, pl. ii, figs. 1la-b. Tetradium peachii var. canadense Foord, 18838, Cont. Micro-Pal., Geol. Surv. Canada, p. 24, pl. vi, figs. 1-1f. Solenopora compacta trentonensis Brown, 1894, Geol. Mag. London, dec. 4, vol. i, p. 146, text fig. 2. Solenopora compacta Winchell and Schuchert, 1895, Geol. Minnesota, Pal., vol. 3, pt. i, p. 80, pl. F, figs. 21-23. Actinostroma trentonensis Weller, 1893, Geol. Surv. New Jersey, Pal., vol. 3, p. 189, pl. vi, fig. 8; pl. vii, figs. 3, 4. MARYLAND GEOLOGICAL SURVEY 193 Description.—This species forms small, sub-globular masses, from one to two inches in diameter. The concentric lamellae are thin and closely packed together, there being in some specimens from 6 to 12 layers in the thickness of two lines. The internal structure is described by Dr. Nicholson as follows: “Composed of radiating capillary tubes, arranged in concentric strata. The tubes vary from 1/12 to 1/20 mm. in size, and are in direct contact throughout, no interstitial tissue of any kind being developed. The tubes are irregular in form, with thin often undulated walls, which are not pierced by any apertures or pores, but are often crossed by more or fewer transverse partitions of ‘tabulae.? Very commonly the tubes exhibit more or fewer inwardly directed partitions, which extend to a greater or less distance into the cavity of the tube, and are the result of the cleavage or ‘ fission ’ of the tubes.” An intensive study of this wide-spread and long-ranged fossil will in all probability reveal the fact that a number of distinct species are included under the name Solenopora compacta. Occurrence.—CHAMBERSBURG LIMESTONE (Caryocystites bed). Fort Loudon and localities south to Blue Spring, Franklin County, Pennsyl- vania. A wide-spread and abundant fossil in almost all of the divisions of the Middle and Upper Ordovician in North America. Collections.—Maryland Geological Survey, U. S. National Museum. SPONGIAE ? (CALCAREOUS ALGAE ?) Genus NIDU_ITES Salter NIDULITES PYRIFORMIS Bassler. Plate XLVI, Figs. 1-5 Nidulites sp. Bassler, 1909, Bull. Virginia Geol. Surv., vol. iia, pl. vii; fig. 11. Nidulites pyriformis Bassler, 1915, Bull. U. S. Nat. Mus., no. xcii, p. 855. Description—tThe body of this interesting organism, which is such an abundant fossil at certain horizons in the Chambersburg limestone of the Appalachian Valley, is pyriform and pedunculate, with an outer 194 SYSTEMATIC PALEONTOLOGY covering of hexagonal, cuplike plates fused or articulated by their edges. On the exterior each plate is deeply concave and marked off at the surface by a sharp wall. The plates are smallest at the narrow end of the organ- ism, but increase in size in the more swollen part where an average diameter for them of one millimeter is the rule. The interior of the organism is hollow (pl. XLVI, fig. 5) and is frequently filled with crystal- line calcite (pl. XLVI, fig. 3). Specimens about 35 mm. in length are the rule, but some individuals attain a length of 50 mm. Small fragments of Nidulites, especially where partly imbedded in the rock, much resemble a massive bryozoan with large zooecia, but examina- tion with a lens reveals the very different nature of the hexagonal plates or cups. The systematic position of Nidulites is still quite uncertain. These bodies were supposed by Salter to be the egg-ribbons of marine gastropods. Later paleontologists placed them among the Protozoa, but to-day the prevalent opinion is that they are allied to Receptaculites, Cerionites, Ischadites and related genera, and are either sponges or calcareous algae. Occurrence —CHAMBERSBURG LIMESTONE (Nidulites bed). Pennsyl- vania, Maryland, and Virginia. Wilson, Pinesburg Station, and other localities in Maryland furnish numerous specimens of the species, em- bedded in the rather massive strata of the Nidulites bed. Collection.—Maryland Geological Survey, U. S. National Museum. Genus RECEPTACULITES Defrance RECEPTACULITES OCCIDENTALIS Salter Plate XLV, Fig. 7 Receptaculites occidentalis Salter, 1859, Canadian Org. Remains, dec. i, p. 45, pl. x, figs. 1-7. Receptaculites occidentalis Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 381, text figs. 354-356. Receptaculites occidentalis Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 135, pl. vi, figs. 2-4. Description.—“ Sponge forming discoid or flattened, saucer-like ex- pansions ; attaining a diameter of 200 mm., and having a thickness vary- ing from 4 mm. at the center of the disk to 12 mm. at the margin. The MaryLanp GroLogicaL SURVEY 195 disk itself composed of vertical rods or spicules, with their extremities expanded and more or less flattened to form the two surfaces of the disk. The shafts of the spicules are cylindrical, about 1 mm. or slightly more in thickness, and separated from each other by interspaces about equal to their own thickness. The arrangement of the terminations of the spicules upon the surface of the disk is in curved, radiating lines, crossing after the manner of the engine-turned ornamentation of a watch. The ex- panded outer extremities of the spicules are rhomboidal in outline, leaving narrow, linear interstices on each side between adjoining spicules. A short distance above the flattened, rhomboidal extremity there are four connecting processes, which join the spicule with each of the adjoining ones. The inner extremities of the spicules are also expanded and joined together to form the inner surface of the disk.”—Weller, 1903. Occurrence-—CHAMBERSBURG LIMESTONE (LHchinospherites bed). Southern Pennsylvania and at Pinesburg Station, Maryland. Black River group of Canada, New Jersey, Kentucky, and Arctic America. Collection.—U. 8. National Museum. PORIFERA crass SPONGIAE Genus RHABDARIA Billings RHABDARIA FRAGILIS (Billings) Rhabdaria fragilis Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 357. Rhabddaria fragilis Rauff, 1894, Paleontographica, vol. xl, p. 245. Description.—*“ Small cylindrical stems, with a rough exterior, and 2 central perforation or canal. At first these were thought to be silicified specimens of Stenopora fibrosa, but when others were procured showing the central canal, it became evident that they could not be thus referred. They have the form of crinoidal columns, but are not jointed. No structure can be made out in thin slices under the microscope.”—Billings, 1865. 196 SYSTEMATIC PALEONTOLOGY Specimens of a ramose bryozoan-like fossil with a central canal have been found at several localities in the Beekmantown of the Appalachian Valley in Maryland and Pennsylvania. These agree in all respects with the species described above by Billings, which’ unfortunately has never been figured. In order to establish the species the original types or speci- mens from the type locality must be further investigated and illustrated. Until this has been done the identification of the species in the Appa- lachian Valley must be considered as provisional. ‘The type specimens are from the Romaine division of the Canadian, Mingan Islands, Quebec. Occurrence.—BEEKMANTOWN Limestone. Lower part above the Stone- henge horizon, just east of Hagerstown, Maryland. Also at the same zone in the Chambersburg quadrangle of Pennsylvania. Collection.—U. S. National Museum. Cenus CAMAROCLADIA Ulrich and Everett CAMAROCLADIA RUGOSA Ulrich Plate XLII, Fig. 6 Camarocladia rugosa Ulrich, 1897, Geol. Minnesota, vol. iii, pt. 2, p. xev, foot note. ' Description.—The fucoid-like remains upon which this species is based appear to be the cast of a branching sponge, although the specimens seldom show structure and appear most frequently as flattened, stony branches with more or less obscure oblique and transverse furrows. These compressed flexuous branches bifurcate sometimes close together and other times far apart. The branches vary from 5 to over 12 mm. in width and are sometimes so crowded in the rock as to form a regular network or matting. In the best preserved examples, the surface is covered with an irregular network of coarse, nodulose threads often arranged longitudinally and generally on one side of the branch only. When removed from the rock the stems are found to be composed of two fairly well-defined portions, (1) a siphuncle-like, subcylindrical rod, with annulations and constrictions 3 to 6 mm. apart, and (2) a series of oblique septa-like partitions, generally two to each annulation, clasp- Marytanp GroLogicaL SuRVEY 197 ing the annulated rod so as to leave about one-third of its circumference exposed to view. Sometimes the rod changes suddenly from one side of the branch to the other. Occurrence. —CHAMBERSBURG LIMESTONE (Tetradium cellulosum bed). Fort Loudon, Franklin County, Pennsylvania. An abundant species in the Decorah shales division of the Black River in Goodhue County, Minnesota, and at the same horizon in Mercer County, Kentucky. Collecttons—Maryland Geological Survey, U. 8. National Museum. Order TETRACTINELLIDA Family HINDIIDAE Genus HINDIA Duncan Hinpra parva Ulrich Plate L, Figs. 11-13 Hindia parva Ulrich, 1889, Amer. Geol., vol. iii, p. 244. Hindia parva Winchell and Schuchert, 1895, Geol. Minnesota, vol. iii, pt. 1, p. 79, pl. G, figs. 7-9. i Hindia parva Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 135, pl. vi, fig. 1. Description.—This small sponge forms free, rounded masses with a smooth surface. Most of the specimens are about 7 mm. in diameter, although this dimension varies between 5 and 10 mm. The internal structure is very similar to the common Hindia sphaeroidalis Duncan of the Silurian and Early Devonian, but the radiating canals of H. parva are somewhat smaller, being not over 0.27 mm. in diameter. More refined methods of study of these sponges will no doubt reveal other important differences. Occurrence.—MartTINsBURG SHALE' (Sinuites bed). Chambersburg, Pennsylvania, and Strasburg, Virginia. Black River of Minnesota and Wisconsin, Trenton of Kentucky, Tennessee, New Jersey and other states. Collections.—Maryland Geological Survey, U. S. National Museum. 198 SYSTEMATIC PALEONTOLOGY COELENTERATA Crass ANTHOZOA Subclass TETRACORALLA Family CYATHOPHYLLIDAE Genus GOLUMNARIA Goldfuss CoLUMNARIA (?) HaLLI Nicholson Plate XUI, Fig. 5 Columnaria alveolata Hall, 1847, Pal. New York, vol. i, p. 47, pl. xii, figs. la-1c. (not Goldfuss). Columnaria (?) halli Nicholson, 1879, Tab. Corals Pal. Period, p. 198, text figs. 28, 2; p. 200, text fig. 29; pl. x, figs. 3, 3a. Columnaria (?) halli Winchell and Schuchert, 1895, Geol. Minnesota, Pal., vol. ili, pt. 1, p. 85, pl. G, figs. 14-16. Description.—“ Corallum forming large massive colonies which vary from a few inches to several feet in diameter, and which are composed of various sized polygonal: corallites, in close contact with one another throughout their entire length. The walls of the corallites are not excessively thickened, and they are so completely amalgamated in con- tiguous tubes that even under the microscope the original lines of demarcation between the tubes can be made out with difficulty or not at all. The large tubes are usually from two to three lines in diameter, though occasionally considerably more than this, and the smaller corallites are of all sizes. Septa marginal, in the form of obtuse longi- tudinal ridges which vary in number from 20 to 40, do not extend to any distance into the visceral chambers, and are not divisible into an alternating longer or short series. Tabulae strong, horizontal and com- plete, about half a line apart or sometimes closer. Mural pores not recognized with certainty.”—Winchell & Schuchert, 1895. Occurrence —CHAMBERSBURG LIMESTONE (Caryocystites bed). From Fort Loudon south to Blue Spring, Franklin County, Pennsylvania. Generally an abundant fossil in the Mohawkian rocks of Canada and the United States. Collections —Maryland Geological Survey, U. 8. National Museum. MARYLAND GEOLOGICAL SURVEY 199 Family ZAPHRENTIDAE Genus STREPTELAS «A Hall STREPTELASMA PROFUNDUM (Conrad) Plate XLII, Figs. 1, 2 Cyathophyllum profundum Conrad, 1848, Proc. Acad. Nat. Sci., Philadelphia, p. 335. Streptelasma profunda Hall, 1847, Pal. New York, vol. i, p. 49, pl. xii, figs. 4a-d. Streptelasma profundum Winchell and Schuchert, 1895, Geol. Minnesota, Pal., vol. iii, pt. i, p. 88, pl. G, figs. 17-19. Description.—* Obliquely turbinate, often slightly curved near the base, expanding above more or less abruptly; cell profoundly deep, ex- tending nearly to the base of the coral; margin of the cup reflexed ; sur- face scarcely marked by transverse rugae; lamellae from 36 to 60, strong, nearly equal to the margin, but distinctly alternating in length within; no transverse dissepiments or celluliferous structure.”—Hall, 1847. This well-marked form can readily be separated from other species of the genus by its deep, visceral cavity, by its sharply defined lateral fos- sulae and great development of the primary septum, and by its septa which are never twisted in approaching the center. Occurrence. CHAMBERSBURG LIMESTONE (Tetradium cellulosum bed). Fort Loudon, Franklin County, Pennsylvania. A characteristic and abundant Black River fossil of the United States and Canada. Collections—Maryland Geological Survey, U. 8S. National Museum. Suborder TABULATA Family CHAETETIDAE Genus TETRADIUM Dana TETRADIUM ? SIMPLEX 2. sp. Plate XXXIII, Figs. 13-15 Description.—The discovery of a coral in the Beekmantown limestone is of especial interest since hitherto no typical representative of the corals has been recorded from strata of this age. The species here noted occurs 200 SYSTEMATIC PALEONTOLOGY abundantly in the lower Beekmantown just above the top of the Stone- henge member, where it appears in lamellose masses on the weathered rock surfaces. Unfortunately all trace of the structure is lost in the solid rock and the generic determination cannot therefore be confirmed by thin sections. The corallites are polygonal, with rather thick walls which sometimes show a distinct line of separation. Three corallites occur on an average in 2 mm. No septa are seen, but their apparent absence may be due to the poor preservation of the specimens. The vertical sections exposed by weathering show no tabulae. If this species should prove to be an early representative of Tetradium it will be readily distinguished from the other species of that genus by its small corallites. Occurrence.—BEEKMANTOWN LimEsTonE. Just above the Stonehenge member. The best specimens were found in the old brick yard on the eastern edge of Hagerstown. Collections.—Maryland Geological Survey, U. 8. National Museum. TETRADIUM SYRINGOPOROIDES Ulrich Plate XX XVIII, Figs. 13-15 Tetradium sp. Bassler, 1909, Va. Geol. Surv., Bull., vol. iia, pl. iv, fig. 2. Tetradium syringoporoides Ulrich, 1910, in Stose, Folio U. S. Geol. Surv., 170, p. 58. Description.—This species, which is very characteristic of the Stones River group, has been known for a number of years by the students of Appalachian geology as the “ single-tubed. Tetradium.” Certain beds of the Stones River limestone are so charged with these tubes that they give the rock a coarse, spongy appearance. Upon weathering the individual tubes stand out in relief like pieces of cord, but in fractured fragments of limestone the tubes are equally distinct, although here appearing as stringers of calcite. Upon close examination the coral nature of this organism becomes evident, for the tubes divide, giving rise to.either two or four individual tubes which, after adhering together for a short dis- tance, separate and in turn subdivide as before. No tabulae are visible MarYLAND GEOLOGICAL SURVEY 201 nor are any signs of septa to be observed until just before a tube divides when the characteristic four septa of Tetradium are developed. A normal corallite is quadrangular and about two-thirds of a millimeter across. Occurrence.—SToNES River Limestone. Abundant especially in the upper division, in the Appalachian Valley. In Maryland exposures along the line of outcrop from Pinesburg Station north through Wilson to the state line exhibit numerous examples. | Collections—Maryland Geological Survey, U. 8. National Museum. TETRADIUM COLUMNARE (Hall) Plate XLI, Fig. 4 Chaetetes columnaris Hall, 1847, Pal. New York, vol. i, p. 68, pl. xxiii, figs. 4, 4a. Tetradium columnare Safford, 1856, Amer. Jour. Sci. and Arts, 2d ser., vol. xxii, p. 237. Description.“ Coral massive, hemispherical or subglobose, consisting of a series of parallel or diverging polygonal tubes; tubes four- or five- sided, simple, without visible transverse dissepiments or connecting pores ; interior of the cells apparently rugose or denticulate. “ The rugose structure within the cell probably indicates the existence of diaphragms which have disappeared. The fossil, in its general form and structure, has the appearance of a Favosites, from which a cursory examination would not induce us to separate it. A closer examination proves that the tubes are usually four-sided, and that there are no con- necting pores in the walls of the cells. These characters had decided me to separate it from the genus Favosites, before knowing fully the char- acters on which the genus Chaetetes is founded. It appears referable to the latter genus from its general similarity to some of the species, the character of quadrangular cells probably being unimportant and not constant. The apparent absence of diaphragms, or transverse dissepi- ments, is perhaps due to their subsequent destruction, or solution and removal.”—Hall, 1847. Occurrence.-—CHAMBERSBURG LIMESTONE (Caryocystites bed). Fort Loudon, Pennsylvania. ' 202 SysteMATIC PALEONTOLOGY Not uncommon in the Trenton rocks of New York, Kentucky, and Tennessee. Similar forms occur in the Black River and Stones River formations of the United States and Canada. Collections.—Maryland Geological Survey, U. 8. National Museum. TETRADIUM CELLULOSUM (Hall) Plate XLII, Figs. 3-5 Phytopsis cellulosum Hall, 1847, Pal. New York, vol. i, pp. 39, 315, pl. ix, figs. la-d. Description.—The principal features of this index fossil of the Low- ville limestone are well shown in Hall’s original illustrations reproduced in the present volume. As is well known, the main specific character of the fossil is the occurrence of the corallites in small bunches which, in the course of growth, form elongated, subcylindrical or compressed stems. These stems sometimes anastomose, forming a network. In transverse sections the generic character of the coral, the quadrangular corallites with four regularly placed septa, is well brought out. This most char- acteristic coral of the Lowville limestone has a wide distribution in New York and Canada and the Appalachian and Ohio valleys. Occurrence.—CHAMBERSBURG LimEsToNE (Tetradium cellulosum bed). Fort Loudon and the railroad cut two miles southwest of Marion, Franklin County, Pennsylvania. Collections.—Maryland Geological Survey, U. 8. National Museum. crass GRAPTOLITOIDEA Order G RAPTOLOIDEA Family DIPLOGRAPTIDAE Genus CLIMACOGRA' TUS Hall CLIMACOGRAPTUS PUTILLUS (Hall) Plate LIT, Figs. 5-7 Graptolithus putillus Hall, 1865, Geol. Surv. Canada, Org. Rem., dec. 2, pp. 27, 44, pl. A, figs. 10-12a. . Climacograptus putillus Ruedemann, 1908, Mem. New York State Mus., vol. xi, pt. 2, pp. 415-419, pl. xxviii, figs. 14, 15, text figs. 368-374, 376, 377. MARYLAND GEOLOGICAL SURVEY 203 Description.—* Rhabdosome very small (9 mm. mostly less) and slender (1-1.3 mm. wide), elliptic in section, widening gradually, possess- ing a gently wavy median furrow on each lateral face. Sicula small (1.3 mm.) and very slender, provided with a short apertural spine; its slender virgella protruding from the rhabdosome. Thecae tubular, little inclined to the axis of the rhabdosome in the proximal half and sub- parallel to it in the distal free half; closely arranged (12-14 in the space of 10 mm. or 32 in 1 inch) ; apertures straight, at right angles to longer axes of thecae. Nemacaulus thin.”—Ruedemann, 1908. A common species of the Ohio and Mississippi valleys, New York, Canada, etc., ranging from the Trenton to the Richmond. Occurrence.—MAanRTINSBURG SHALE (Corynoides bed). Chambers- burg, Pennsylvania, and Williamsport, Maryland. Collections —Maryland Geological Survey, U. 8. National Museum. CLIMACOGRAPTUS SPINIFER (Ruedemann) Plate LIT, Figs. 3, 4 Climacograptus typicalis mut. spinifer Ruedemann, 1908, New York State Mus. Mem., vol. xi, pt. 2, pp. 411, 412, pl. xxviii, figs. 8, 9, text fig. 236. Climacograptus spiniferus Ruedemann, 1912, New York State Mus., Bull. 162, p. 84. Description.—This species is distinguished from the well-known Cli- macograptus typicalis Hall, which it most closely resembles, in the presence of two straight, thin spaces and in the closer arrangement of the thecae, the majority of the specimens having 14 thecae in 10 mm. In the presence of the two spines this species resembles Climacograptus bicorms Hall, but in the latter species these spines grew from the first two thecae and are not prolongations of the sicular spines as in C. spinifer. Occurrence.—MartinsBurG SHALE (Corynoides bed). Chambers- burg, Pennsylvania, and Williamsport, Maryland. ‘Trenton shale of eastern New York. Collections—Maryland Geological Survey, U. S. National Museum. 204 SYSTEMATIC PALEONTOLOGY CLIMACOGRAPTUS BICORNIS (Hall) Plate LIII, Fig. 1 Graptolithus bicornis Hall, 1847, Pal. New York, vol. i, p. 268, pl. Ixxiii, figs. 2a-s, Climacograptus bicornis Elles and Wood, 1906, Mon. British Grapt., pt. 5, pp. 193, 194, fig. 125, pl. 26, figs. 8a-f. Climacograptus bicornis Ruedemann, 1908, Mem. New York State Mus., vol. xi, pt. 2, pp. 433-437, pl. xxviii, figs. 24-26, figs. 404, 405. Description.—*‘ Synrhabdosome not observed. Rhabdosome linear in the middle and antisicular portions; attaining great length (10 cm. and more) ; gradually widening from the sicular extremity to a width of 2.6+mm., attained in about 30 mm. and maintained close to the anti- sicular extremity. The former extremity is always armed with two diverging lateral spines, which grow from the first two thecae, and the’ virgella which greatly varies in length. The sicula is 1 mm. long, its greater portion embedded. ‘The thecae number 12 in the sicular region and ‘seven in the mature part and overlap about one-third their length; their proximal walls are curved, the free distal wall straight and parallel. to the axis of the rhabdosome. The apertural margins are horizontal, the apertural excavations wide (one-third length of theca) and attaining in depth one-fourth the width of the rhabdosome in mature part, and one-third in the earlier part. Nemacaulus not observed.”—Ruedemann, 1908. The typical form of this wide-spread species has been recognized in North America only in the Chazyan, but varieties or very closely related species occur in younger formations of the Ordovician. In southern Pennsylvania and Washington County, Maryland, the upper beds (Eden) of the Martinsburg shale furnish a species of Climacograptus exhibiting the diverging points at the base characteristic of C. bicornis. Occurrence—Martinspurc SHALE (Eden division). Washington County, Maryland. Collections.—Maryland Geological Survey, U.S. National Museum. MARYLAND GroLoagicaL SURVEY 205 Genus DIPLOGRAPTUS McCoy DIPLOGRAPTUS VESPERTINUS (Ruedemann) Plate LILI, Figs. 2-4 Diplograptus pristis (parte) Hall, 1847, Pal. New York, vol. i, pl. 1xxii, figs. 1, la, 1b, 1k, 11. Diplograptus foliaceus mut. vespertinus Ruedemann, 1908, Mem. New York State Mus., vol. xi, pt. 2, pp. 352-354, pl. xxv, figs. 4, 5, 18, text figs. 296-298. Description. Synrhabdosome not observed. Rhabdosomes as a rule short (15 mm., greatest length observed 42 mm.), widening gradually from an initial width of 1 mm. to a maximum width of 2.5 which is attained in a distance of 15 mm. from the sicular extremity and then maintained. Sicula not observed. Sicular extremity furnished with a short blunt virgella (about .4 mm. long) and two equally short straight lateral spines. Thecae numbering 11 to 13 in 10 mm. (30-32 in 1 inch), inclined at an angle of 30°-40°, overlapping a little more than one-third, the outer margin distinctly convex, the proximal part frequently slightly concave. The aperture horizontal, concave, the interthecal excavation about one-fourth the width. Nemacaulus very thin and inconspicuous within the rhabdosome and not seen protruding beyond the antisicular end.”—Ruedemann, 1908. The types are from the Normanskill (Chazyan) shales of New York and the species has been identified also from the Trenton shales of the same state. Occurrence.—MartinsBurG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, ‘Pennsylvania, and in the same horizon on the west slope of Rickard “Mountain, _ Maryland. Collection.—U. 8S. National Mase, 1 206 SYSTEMATIC PALEONTOLOGY POSITION UNCERTAIN Genus CORYNOIDES Nicholson CoRYNOIDES CALICULARIS Nicholson Plate LII, Figs. 1, 2 Graptolite germs Hall, 1859, Pal. New York, vol. iii, p. 508, fig. 7. Corynoides calicularis Nicholson, 1867, Geol. Magazine, vol. iv, p. 108, pl. vii, figs. 9-11. Corynoides calicularis Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, pp. 52, 214, pl. xvi, figs. 12, 13. Corynoides calicularis Ruedemann, 1908, New York State Museum, Mem., vol. xi, pt. 2, pp. 234-237, pl. xiii, figs. 1, 6-8, text figs. 122-132. Description.— Rhabdosome short (6-8 mm.) and relatively broad (about 1 mm.), of uniform width, consisting of a sicula and three thecae. Sicula small: (2 mm.), conical, without apertural processes, in mature specimens slightly recurving, suspended from a long and slender nema. Thecae slender tubes of uniform width, all originating close to the sicula, arranged in a bundle which forms an angle of 50° with the sicula. Apertures straight, normal to the axes of the thecae, all adjoining at the distal extremity of the rhabdosome, each provided with a pair of usually curved strong spines, which often appear to be raised upon a tonguc- like process. Nema thin and filiform.”—-Ruedemann, 1908. This curious little graptolite is so small and usually so poorly preserved in the shales that its presence is often not detected without careful search. Weathered shale fragments in which the color of the fossil has been changed to reddish brown or even white, show specimens to the best advantage. Occurrence.—MartiInspura SHALE (Corynoides bed). Chambers- burg, Pennsylvania, Williamsport, Maryland, and in other outcrops to the south. Chazyan (Normanskill) shales, New York, and south in the Appalachian Valley to Tennessee. Collection.—U. 8. National Museum. MARYLAND GEOLOGICAL SURVEY 207 ECHINODERMATA crass CYSTOIDEA Family ECHINOSPHAERITIDAE Genus ECHINOSPHAERIIES Wahlenberg ECHINOSPHAERITES AURANTIUM AMERICANUM Ni. var. Plate XLV, Figs. 15-20 Compare Echinus aurantium Gyllenhal, 1772, Kongl. Vet. Akad. Handl., vol. xxxiii, p. 245, pl. viii, figs. 4, 5; pl. 9, figs. 6-9. Description.—One of the most interesting paleontological discoveries in the Ordovician limestone of the Appalachian Valley of Pennsylvania and Maryland was that of numerous large globular cystids belonging to the genus Hchinospherites, which had heretofore not been recognized in America. One division of the Chambersburg limestone is so crowded with these cystids that the name Echinospherites bed has been applied toit. At first sight these cystids appear as so many boulders in the rock, and indeed in the past the strata containing them have doubtless been considered as conglomerates. Unweathered specimens show no definite structure to these organisms other than that they appear to be globular masses with a thick, smooth outer covering. When weathered, however, they are seen to be composed of irregularly arranged plates with the numerous canals forming the pore rhombs especially visible. The various species of Hchinospherites seem to have been distinguished by European paleontologists mainly by their differences in shape. Com- paring the figures on pl. XLV with typical L’. awrantium from the Middle Ordovician of Esthonia, Russia, it will be noted that the American form is larger and more ovate. For this reason it has been thought best to distinguish it as a variety pending a thorough study of the group by some specialist. The common name of “ crystal apple” applied to species of Echinospherites in Europe is very appropriate, first because of their shape and second because the interior of the cystid is often a mass of calcite crystals. American specimens are often found with a crystalline interior. 14 208 SysTEMATIC PALEONTOLOGY This large globular cystid, as noted above, is so abundant in a lower division of the Chambersburg limestone that it has received the name of the Echinospherites bed. The reappearance of the species in the Chris- tiania bed was noted only in southern Pennsylvania where a few speci- mens were found at the higher horizon. Occurrence. CHAMBERSBURG LimESTONE (Echinospherites bed). Appalachian Valley of Pennsylvania, Maryland, West Virginia, and Virginia. In Maryland specimens have been found at-Pinesburg Station and northward along the line of outcrop through Wilson to the state line. The same form reappears, although rarely, in the Christiania bed of the Chambersburg limestone in southern Pennsylvania. Collections.—Maryland Geological Survey, U. S. National Museum. Genus CARYOCYSTITES Von Buch CARYOCYSTITES sp. Plate XLI, Fig. 7 Description.—The strata of the Chambersburg limestone underlying the Lowville division contain plates of a species of the cystid genus Caryocystites so abundantly that the name Caryocystites bed has been applied to them. The calyx of this cystid has not yet been found, but the plates are easily recognized by the elevated, prominent pore rhombs on their external surface. When weathered the plates also show the pores or canals connecting with the pore rhombs and passing vertically through the plate. Occurrence.—CHAMBERSBURG LIMESTONE (Caryocystites bed). Fort Loudon and south to Blue Spring, Franklin County, Pennsylvania. Collections—Maryland Geological Survey, U. S. National Museum. MARYLAND GEOLOGICAL SURVEY 209 Crass CRINOIDEA Order CAMERATA Family RETEOCRINIDAE | Genus RETEOCRINUS Billings RETEOCRINUS ? sp. Plate XXXVII, Fig. 5 Description.—Small plates showing six or seven rays are not uncommon on the surface of the thin-bedded Frederick limestone. These are of echinoderm nature, but whether cystid or crinoid cannot be determined. They appear most like the minute pieces forming the pliant integument of the interbrachial areas in such crinoidal genera as Reteocrinus. Occurrence.—FREDERICK Limestone. In the vicinity of Frederick, Maryland. , Collections—Marvland Geological Survey, U. S. National Museum. Order INADUNATA Family CYATHOCRINIDAE Genus GCARABOCRINUS Billings CARABOCRINUS sp. Plate XLI, Fig. 10 Description.—Associated with the small plates of the cystid Caryo- cystites in the lowest bed of the Chambersburg limestone are larger, strongly marked plates of a crinoid. These bear the characteristic mark- ‘ings of the genus Carabocrinus, and as such plates are known only from this division of the Chambersburg limestone an illustration of one has been given on pl. XLI as a characteristic, although unnamed fossil. Occurrence-—CHAMBERSBURG LimESTONE (Caryocystites bed). Fort Loudon south to Blue Spring, Franklin County, Pennsylvania. Collections.—Maryland Geological Survey, U. 8. National Museum. 210 SYSTEMATIC PALEONTOLOGY Family HETEROCRINIDAE Genus HETEROGRINUS Hall HETEROCRINUS HETERODACTYLUS Hall Plate LIII, Figs. 6, 7 Heterocrinus heterodactylus Hall, 1847, Pal. New York, vol. i, p. 279, pl. Ixxvi, figs. la-o. Heterocrinus heterodactylus Meek, 1873, Geol. Surv. Ohio, Pal., vol. i, p. 12, pl. i, figs. la-b. Description.—* Body short, rounded, subcylindrical, tapering above and below; pelvis composed of five small pentagonal plates, which are succeeded by the same number of larger costal plates, and these again by five scapulars ; arms irregularly subdivided ; column pentagonal, composed of thick joints, which are nodulose at the angles; joints alternating in size as they approach the pelvis. “This is a peculiar species, remarkable for the small size of the body when compared with the column. The irregularity of the arrangement of the plates in the arms and fingers is likewise a striking characteristic of the species, which is constant in two specimens from different localities. In one of the arms, the scapular plate supports a regular series of six or . more plates of similar form without division. The arms at the right and left of this one are again unlike each other. The one on the left has three regular and gradually diminishing joints above the scapular, and of the same form; the last one supports the cuneiform joint, which again supports a double row of joints (or a pair of fingers). The arm on the right of the first mentioned consists of a pair of quadrangular joints, each of which supports a cuneiform joint. In the remaining two arms, no plates have been traced beyond the scapulars, and consequently the entire form of the species cannot be determined. Sufficient is visible, however, to show the irregular character of the arms, from which its name is given.”—Hall, 1847. Occurrence-—Martinspura SHALE (Eden division). Pennsylvania and Maryland. A splendid mold of a well-preserved, entire calyx with a considerable column attached was found at Jordans Knob, one and one- MARYLAND GEOLOGICAL SURVEY 211 half miles northeast of Fort Loudon, Pennsylvania. Eden shale of New York and the Ohio Valley. Collections.—Maryland Geological Survey, U. 8. National Museum. Family DENDROCRINIDAE Genus MEROCRINUS Walcott MEROCRINUS sp. Plate LITI, Fig. 5 Description.—Only stem segments of this crinoid have been found in the upper Martinsburg shale, but the genus itself is so characteristic of the Trenton and Eden formations that it was thought advisable to figure an example as a characteristic fossil. It is possible that the segments here illustrated will be found to belong to the only known Eden species, M. curtus Ulrich, from the Cincinnati region. Occurrence.—MaRTINSBURG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, and other localities in southern Pennsylvania, and in the sandy debris on the west slope of Rickard Mountain, Washington County, Maryland. Collections.—U. 8. National Museum. CLASS STELLEROIDEA Family HUDSONASTERIDAE Genus HUDSONASTER Stiirtz HUDSONASTER CLARKI 0. sp. Plate LIII, Fig. 8 Description.—This new species is based upon two specimens preserved as a mold in sandy shale and exhibiting the actinal side. The species is closely related to H. matutinus (Hall) from the Trenton, and is indeed probably descended from it, but the Eden form differs in having coarse tuberculations on the axillary plates and more slender and mote regu- larly tapering arms. Further differences will no doubt be detected when better specimens are found, but the above seem sufficient to discriminate the species. 212 SYSTEMATIC PALEONTOLOGY The specific name is in honor of the late Professor William Bullock Clark in appreciation of his work upon fossil echinoderms. Occurrence-—MartTInsBurG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania. Collection.—U. S. National Museum. MOLLUSCOIDEA crass BRYOZOA Order CY CLOSTOMATA Family DIASTOPORIDAE Genus CORYNOTRYPA Bassler CoRYNOTRYPA INFLATA (Hall) Plate XLVII, Figs. 15-17 Alecto inflata Hall, 1847, Pal. New York, vol. i, p. 77, pl. xxvi, figs. 7a, b. Stomatopora inflata Ulrich, 1893, Geol. Minnesota, vol. iii, p. 117, pl. i, figs. 13-21. Corynotrypa inflata Bassler, 1911, Proc. U. S. Nat. Mus., vol. xxxix, p. 515, text figs. 12-14. Description.— Zocecia resembling those of Hippothoa, short and wide, pyriform, the proximal end contracted and springing from the under side of the anterior end of the cell beneath ; eight or ninein 5mm. Apertures circular, direct, with a peristome, about 0.09 mm. in diameter, situated near the anterior end. Mural perforations minute and but rarely preserved. “Tn the Trenton or typical form of this species the zocecia, as a rule, are less swollen and the adnate zoarium divides less frequently than in the better known Cincinnati form. In the latter, therefore, the network is closer, and occasionally the growth is so luxuriant that the rows cross each other to such an extent that but little space is left between the cells. No distinction, however, can be based upon these characters since, when good series of specimens are studied, it is found that among those from MARYLAND GEOLOGICAL SURVEY 213 Trenton localities some have more than commonly swollen and crowded cells, while in some of those from the geologically higher localities the erowth is lax and the zocecia comparatively narrow.”—Ulrich, 1893. Occurrence —CHAMBERSBURG LIMESTONE (Nidulites bed). Wilson, Maryland. Found in the Black River-Richmond at many localities in the United States and Canada. Collections——Maryland Geological Survey, U. 8. National Museum. CoRYNOTRYPA DELICATULA (James) Plate XLVII, Figs. 12-14 Hippothoa delicatula James, 1878, The Paleontologist, No. 1, p. 6. Stomatopora tenuissima Ulrich, 1893, Geol. Minnesota, vol. iii, pt. 1, p. 116, pl. i, figs. 16, 17. Stomatopora proutana Ulrich, 1898, Geol. Minnesota, vol. iii, pt. 1, p. 117, pl. i, figs. 8-12. Corynotrypa delicatula Bassler, 1911, Proc. U. S. Nat. Mus., vol. xxxix, p. 506, text figs. 3a, 4-7. Description.—This neat incrusting fossil is extremely abundant in America where it is known in most of the Ordovician formations, begin- ning with the Stones River. The zocecia vary considerably in size in the different forms of the species, but maintain the same relative proportions. In both the large and small forms the zoarium is incrusting and con- sists of uniserially arranged, slender, club-shaped zocecia, increasing gradually in size from the narrow proximal end to the rounded anterior portion. The aperture is small, subterminal, with a slightly elevated border, and about one-third the diameter of the anterior third of the zocecia. The measurements for the two forms are as follows: Typical specimens have zocecia 0.04 mm. in diameter at the proximal end, increas- ing to 0.12 to 0.15 mm. at the widest part of the rounded anterior por- tion. The zocecia vary from 0.6 to 0.8 mm. in length, and 8 to 10 occur in 5 mm. The larger form varies from 0.8 to 1.1 mm. in length and from 0.2 to 0.8 mm. in diameter at the anterior portion. The stolon is of variable length. The angle of divergence in both large and small zocecia is about 15°. 214 SYSTEMATIC PALEONTOLOGY Occurrence CHAMBERSBURG LIMESTONE (Nidulites bed). Wilson, Maryland. Stones River-Richmond at many localities in the United States and Canada. Collections—Maryland Geological Survey, U. 8. National Museum. Genus BERENICEA Lamouroux BERENICEA VESICULOSA Ulrich Plate LITI, Fig. 9 Berenicea vesiculosa Ulrich, 1882, Jour. Cincinnati Soc. Nat. Hist., vol. v, p. 158, pl. vi, fig. 5. Description.—“ Zoarium adnate, very delicate, growing usually upon smooth crinoid columns. Cells showing distinctly upon the surface as elliptical convex spaces, with the circular aperture situated upon the forward slope of the same. The cells are closely arranged in rather irregularly alternating series; measured along the length of the cells, about eight may be counted in the space of one inch; and across their width 11 or 12 occupy the same space.”—Ulrich, 1882. Occurrence.-—MartinsBurG SuALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania. Eden shale of the Ohio Valley. Collections.—Maryland Geological Survey, U. S. National Museum. Order TREPOSTOMATA Family MONTICULIPORIDAE Genus ORBIGNYELLA Ulrich and Bassler ORBIGNYELLA WETHERBYI (Ulrich) Plate XLII, Figs. 7, 8 Monticulipora wetherbyi Ulrich, 1882, Jour. Cincinnati Soc. Nat. Hist., vol. v, p. 239, pl. 10, figs. 4-4b. Monticulipora wetherbyi Ulrich, 1898, Geol. Minnesota, vol. iii, p. 218; pl. xv, figs. 7, 8. Description.—Zoarium attached, forming thin crusts or small de- pressed conical masses with slightly monticulose, or smooth surfaces. Zocecia polygonal, with very thin walls, those of the ordinary size with a MARYLAND GEOLOGICAL SURVEY 215 diameter of 0.25 mm. Clusters of larger zocecia form the monticules, or are scattered over the surface of the smooth zocecia at intervals of about 2.5 mm., measuring from center to center. These zocecia measure from 0.30 to 0.38 mm. in diameter. At the center of the monticules a few mesopores, or more probably young zoccia, are present. Acanthopores rather large and numerous. In longitudinal sections the zocecial tubes exhibit thin walls with the characteristic granulose structure. The diaphragms are curved and occur at intervals of a tube-diameter or more in the lower half of the tubes and about one-third that distance apart near the surface. In tangential sec- tions the zocecial walls are angular and thin with a strong acanthopore at most of the angles. The method of growth, small, angular, thin-walled zocecia, large acanthopores, granulose wall structure and the presence of curved diaphragms are the important features of this characteristic and wide-spread Lowville fossil. Occurrence—CHAMBERSBURG LimESTONE (Tetradium cellulosum bed). Several localities south of Chambersburg in Franklin County, Pennsylvania. Lowville limestone of the Ohio Valley, etc. Collections.—Maryland Geological Survey, U. S. National Museum. Genus PRASOPORA Nicholson and Etheridge, Jr PRASOPORA INSULARIS Ulrich Plate XLIV, Figs. 15-17 Prasopora insularis Ulrich, 1898, Geol. Minnesota, vol. iii, p. 251, pl. 16, figs. 18-23. Description.—* Zoarium small, discoid, plano- or concavo-convex, com- monly from 15-20 mm. in diameter and 5 or 6 mm. in height. In a very large example these dimensions are respectively 28 and 12 mm., while in the smallest seen they are 1.5 and 0.5 mm. Under surface with a central sear, and beyond it delicate radiating lines, fine concentric striae, and, at intervals indicating stages of growth, stronger wrinkles. Very often the zoaria are evidently made up of distinct superimposed layers, but these are not usually distinguishable internally. Upper or convex surface with- out monticules, but exhibiting, at intervals of about 4 mm., distinct 216 SYSTEMATIC PALEONTOLOGY clusters of large zocecia. Generally, at the center of each of these clusters, the mesopores which are small and in nearly all cases just about numerous enough to isolate the zocecia, are gathered into groups of varying size. Zocecial apertures circular, those in the clusters attaining a diameter of 0.4 mm., while those of the smaller size in the inter-macular spaces average about 0.22 mm., with 11 or 12 in 3 mm. “Internal Characters: The first peculiarity to be noticed in tan- gential sections is the relatively great abundance of the mesopores. In most specimens they form a complete ring around the zocecia, and it is chiefly the large cells in the clusters that are occasionally in contact at limited points. The zocecial walls are thin. The cystiphragms are more numerous and extend to a less distance from the walls than in any other American species. The opening left by them is of various shapes, gen- erally subangular, and often removed from the walls. True acanthopores have not been detected. “In vertical sections the abundance of the mesopores, the narrowness of the cystiphragms, and the unusual crowding of the tabulation in both sets of tubes, are the distinctive features. In the mesopores the average number of diaphragms in 1 mm. is over 25, while the cystiphrams may number as high as 20 in 1 mm., though the average is not likely to be over 15 in that space.”—Ulrich, 1893. Occurrence-—CHAMBERSBURG LimEestonE (Echinospherites bed). Pinesburg Station, Maryland. This species has hitherto been known only from the lower Trenton (Prosser limestone) of Minnesota. Collections.—Maryland Geological Survey, U. 8. National Museum. PRASOPORA CONTIGUA Ulrich Plate XLVII, Figs. 7, 8 Prasopora contigua Ulrich, 1886, Fourteenth Ann. Rept. Geol. Nat. Hist. Surv. Minnesota, p. 87. , Prasopora contigua Ulrich, 1893, Geol. Minnesota, vol. iii, p. 249, pl. xvi, figs. 24-26. Description.—“ Zoarium hemispheric, base flat or slightly concave, usually less than 30 mm. in diameter. Zocecia with very thin walls and MaryYLAND GEOLOGICAL SURVEY 217 polygonal apertures, 10 or 11 of the average size in 3 mm. Clusters of zocecia, some of them attaining a diameter of 0.37 mm., occur at interva!s of less than 4mm. Mesopores comparatively few, often difficult to detect at the surface. “Internal Structure: Tangential sections show that the zoccial walls are polygonal and very thin, with neighboring cells in contact, except at many of the angles of junction, these being occupied by one or two small mesopores. The latter often form very inconspicuous clusters at the center of the groups of large zocecia, but in the intermediate spaces not over half of the angles of junction between the ordinary zocecia are occupied by mesopores. A few very small acanthopores are developed. The opening left by the cystiphragms is generally of ovate form and more often eccentric than central in its position within the tube cavity. “Vertical sections are peculiar chiefly because they exhibit a marked decrease in the number of mesopores when compared with other species of the genus.”—Ulrich, 1893. Occurrence.—CHAMBERSBURG LIMESTONE (Nidulites bed). Pennsyl- vania, Maryland, and Virginia. The cliffs along Conococheague Creek at Wilson, Maryland, exhibit specimens of this bryozoan. A not uncom- mon fossil of the Decorah shale division of the Black River group of Minnesota. Collections.—Maryland Geological Survey, U. S. National Museum. Family CONSTELLARIIDAE Genus DIANULITES Eichwald DIANULITES PETROPOLITANUS Dybowski Plate XLIV, Figs. 6, 7 Dianulites petropolitanus Dybowski, 1877, Die Chaetetiden der Ostbaltischen Silurform., p. 24, pl. 1, figs. 4, 5. Dianulites petropolitana Bassler, 1911, Bull. U. S. Nat. Mus. No. 77, pp. 232, 237, pl. ii, figs. 4-6a; pl. x, figs. 7-11; text figs. 129-132. Monotrypa (Chaetetes ?) cumulata Ulrich, 1893, Geol. Minnesota, vol. iii, pt. 1, p. 307, pl. xxvii, figs. 26, 27. Description.—Zoarium massive, usually hemispheric with a slightly concave, epithecated base, and about 2.5 em. wide, but ranging from this 218 SYSTEMATIC PALEONTOLOGY to large expansions 10 or more centimeters across. Some specimens are of irregular shape, but almost always show their origin from the usual hemispheric forms. Celluliferous side usually smooth, but sometimes divided into polygonal, usually hexagonal, areas bounded by crestlike elevations formed of mesopores. At the center of these areas is a similarly elevated cluster of mesopores forming the macula. Zocecia thin-walled, polygonal, averaging four in 2mm. Mesopores few, restricted usually to the macula and to the edges of the polygonal areas noted above. Acan- thopores absent. Diaphragms placed at irregular intervals in the zocecial tubes, but usually at distances varying between one and two tube diam- eters. In the mesopores three diaphragms occur in a distance of their own diameter. Walls exhibiting the minute granules seen in the typical species of Dianulites. Occurrence—CHAMBERSBURG LIMESTONE (LEchinospherites bed). Pinesburg Station, Maryland. Middle Ordovician of Esthonia, Russia, and Goodhue County, Minnesota (Prosser limestone). Collections.—Maryland Geological Survey, U. 8. National Museum. Family TREMATOPORIDAE Genus HEMIPHRAGMA Ulrich HEMIPHRAGMA IRRASUM (Ulrich) Plate XLIV, Figs. 1-5 Batostoma irrasa Ulrich, 1886, Fourteenth Ann. Rept. Geol. Nat. Hist. Surv. Minnesota, p. 94. Hemiphragma irrasum Ulrich, 1893, Geol. Minnesota, vol. iii, p. 299, pl. xxiv, figs. 5-19. Hemiphragma irrasum Bassler, 1911, Bull. U. S. Nat. Mus., No. 77, pp. 284- 286, text figs. 172, 173. Description.—“ Zoarium consisting of small, subcylindrical, frequently and rather irregularly dividing branches, commonly 5 or 6 mm. in diam- eter, but varying from 4 to 8 mm., the latter extreme probably only when an extra layer of tubes has grown over the original branch. Monticules wanting, but under fully matured conditions the surface is abundantly spinulose. Zocecia with subangular apertures and thin walls when young, MarybLanp GEOLOGICAL SURVEY 219 and with smaller, subcircular or oval apertures and more or less thick walls in fully matured examples ; arrangement of apertures rather regular in rows about small solid spots, in the immediate vicinity of which the zocecia may be of larger size than elsewhere; seven to nine in 3 mm. Interspaces apparently solid and generally with shallow irregular depres- sions in most specimens, but in very young stages a variable number of irregular mesopores may be recognized. Acanthopores numerous, two or more to each zocecium, situated in the angles of junction and inter- spaces, and increasing in size with age. They are large and a conspicuous external feature of well-preserved mature examples. “ Internal Characters: In the axial region of vertical sections the tubes have thin and irregularly fluctuating walls, and few or no diaphragms. The latter are complete here and the proximal end of the tube expands to full size with unusual rapidity. In the peripheral region, which is narrow and abruptly distinguished from the axial, the walls are more or Jess thickened, and the tubes intersected by semi-diaphragms, about four in 0.56 mm. I have satisfied myself that all the transverse partitions in this outer part of the zocecial tubes are really incomplete. That many may appear entire in sections is only because their inner edge happens to be vertical instead of horizontal. Mesopores are difficult to make out in these sections, being short and usually filled, in part at least, with solid tissue. In the axial part of transverse sections the tubes are un- usually irregular and their walls comparatively thick.”—Ulrich, 1893. Occurrence.—_CHAMBERSBURG LIMESTONE (Echinospherites bed). Sev- eral localities in southern Pennsylvania and at Pinesburg Station, Mary- land. Black River and Early Trenton of the Upper Mississippi Valley. Collections.—Maryland Geological Survey, U. 8. National Museum. Genus DIPLOTRYPA Nicholson DIPLOTRYPA ? APPALACHIA 0. sp. Plate XLVII, Figs. 9-11 Description.—Zoarium a small hemisphere or subconical mass averag- ing 20 mm. in width and 10 to 15 mm. high. The under surface exhibits 220 SYSTEMATIC PALEONTOLOGY extremely small tubes which indicate that the reference of the fossil to the Bryozoa may be incorrect. The upper surface shows extremely large openings for a bryozoan, averaging 1 mm. in diameter, with thin walls. In thin sections these cells are seen to be separated by small, irregular mesopore-like structures. Vertical sections are particularly interesting because here the rapid increase in diameter of the tubes from the minute pores of the base to the wide openings of the outer part is well shown. The walls in such sections are seen to be thin and slightly undulating. No diaphragms are developed in either the larger or smaller tubes. It is possible that more extended study of this organism will show it to be a coral related to Lichenaria, but most of the evidence at present seems to indicate its relationship to the Bryozoa. Occurrence—CHAMBERSBURG Limxstone. This fossil and Nidulites pyriformis are the two most abundant and characteristic species ot the Nidulites bed of the Chambersburg formation. The comparatively large tubes of this bryozoan may be seen in weathered cross-sections wherever the more massive layers of the Nidulites beds are exposed. Pinesburg and Wilson, Maryland, afford numerous specimens. Collections.—Maryland Geological Survey, U. S. National Museum. Genus BATOSTOMA Ulrich Batostoma sJAmMEs1 Nicholson Plate LIV, Figs. 1, 2 Chaetetes jamesi Nicholson, 1874, Quart. Jour. Geol. Soc. London, vol. xxx, p. 506, pl. xxix, figs. 10, 10b. Chaetetes jamesi Nicholson, 1875, Pal. Ohio, vol. ii, p. 200, pl. xxi, figs. 11, lla. Monticulipora (Heterotrypa) jamesi Nicholson, 1881, Genus Monticulipora, p. 147, figs. 25, 26. + Batostoma jamesi Cumings, 1908, 32d Ann. Rep. Dep. Geol. Nat. Res. Indiana, p. 775, pl. vii, figs. 8, 8a; pl. viii, fig. 1; pl. xxvii, figs. 6, 6a. Description.—Zoarium of small, rounded, solid stems marked at the surface by large oval zocecia, rather conspicuous acanthopores and numer- ous mesopores. In tangential sections the walls in the mature region consist of thick, dark rings of dense tissue usually widely separated from MARYLAND GEOLOGICAL SURVEY 221 each other by angular, irregularly shaped mesopores. Embedded in these walls numerous acanthopores may be noticed. In longitudinal sections the zocecia are provided with rather infrequent complete diaphragms and mesopores with partitions which are four or five times as numerous. Occurrence.—MartTInsBuRG SHALE (Eden division). Abundant and characteristic in the Eden shale of the Ohio Valley. Impressions of 2 ramose bryozoan in the upper part (Eden) of the Martinsburg shale at Jordans Knob, one and one-half miles northeast from Fort Loudon, Pennsylvania, and Cowans Gap, five miles northeast of McConnellsburg, Pennsylvania, have the external features of this species. Collections.—Maryland Geological Survey, U. 8S. National Museum. Family BATOSTOMELLIDAE Genus BYTHOPORA Miller and Dyer Byrwopora arctipora (Nicholson) Plate LIT, Figs. 11-13 Ptilodictya ? arctipora Nicholson, 1875, Ann. Mag. Nat. Hist., 4th ser., vol. xv, p. 180, pl. xiv, figs. 4-4b. Ptilodictya ? arctipora Nicholson, 1875, Pal. Ohio, vol. ii, p. 262, pl. xxv, figs. 9-9b. Bythopora arctipora Bassler, 1906, Proc. U. S. Nat. Mus., vol. xxx, p. 90, pl. ii, figs. 1, 2. Description.—This, minute species is characterized by its long, slender, cylindrical branches, a millimeter or less in diameter, made up of zocecial tubes which open at the surface in elongate, often attenuate, orifices. The internal structure is that of the genus Bythopora, that is, the zoccial walls are fused in the mature region, diaphragms are practically absent, the apertures are oblique and narrowed above, and the interspaces are canaliculate. Mesopores are present but small, and on account of the small size and little development of the zocecia in this species, they are - inconspicuous. Occurrence.—MARTINSBURG SHALE (Eden division). An abundant and characteristic Eden fossil of the Ohio Valley. Not so abundant in 222 SYSTEMATIC PALEONTOLOGY the upper part (Eden) of the Martinsburg shale at Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania, and west slope of Rickard Mountain, Washington County, Maryland. Collections.—Maryland Geological Survey, U.S. National Museum. Family HALLOPORIDAE Genus HALLOPORA Bassler HALLOPORA ONEALLI SIGILLARIOIDES (Nicholson) } Plate LITI, Fig. 10 Chaetetes sigillarioides Nicholson, 1875, Pal. Ohio, vol. ii, p. 203, pl. xxii, figs. 9, 9a. Callopora sigillarioides Nickles, 1905, Kentucky Geol. Surv., Bull. v, p. 50, pl. ii, figs. 10, 11. Callopora onealli sigillaroides Bassler, 1906, Proc. U. S. Nat. Mus., vol. xxx, pl. vi, figs. 3, 4. Description.—Zoarium ramose, consisting of narrow, dichotomously dividing branches from 2 to 4 mm. in diameter. Surface of branches usually smooth, although occasionally the clusters of larger cells (maculae) are slightly elevated. Apertures of zocecia oval, about six in 2 mm. measuring along the length of the branch, and eight in the same space transversely with their longer diameter in the direction of the branch. Mesopores numerous. Diaphragms few in the axial region of the tubes, but rather numerous in the mature zone. In the mesopores the diaphragms are closely spaced throughout their length. Occurrence.—MartinsBurG SHALE (Eden division). Very abundant and characteristic of the Eden shale in the Ohio Valley. Upper part (Eden) of Martinsburg shale at Jordans Knob, one and one-half miles northeast of Fort Loudon; Cowan’s Gap, five miles northeast of McCon- nellsburg, and Tuscarora Mountain, two and one-half miles southeast of McConnellsburg, Pennsylvania. The corresponding horizon in Maryland on Rickard Mountain, Washington County, also furnishes specimens. In all of the eastern localities the species occurs as molds in the sandy matrix, but the preservation is so good that gutta percha squeezes readily show all of the specific characters of the surface. Collections.—Maryland Geological Survey, U. S. National Museum. MARYLAND GEOLOGICAL SURVEY 223 Order CRYPTOSTOMATA Family PTILODICTYONIDAE Genus ESCHAROPORA Hall EScHAROPORA CONFLUENS Ulrich Plate XL, Figs. 11-14 Escharopora confluens Ulrich, 1893, Geol. Minnesota, vol. iii, p. 171, pl. xiii, figs. 1-11. Description.—* Zoarium branching, the smallest seen less than 25 mm. high, with the branches averaging about 2.5 mm. in width; the largest fragments indicate a hight of from 80 to 120 mm., and in these the width of the branches varies from 4 to 8 mm. The two surfaces of the branches are generally obtusely ridge-shaped, and in the largest a row of monti- cules, or simply clusters of large cells, occurs on the summit of the ridge. Edges thin and sharp, commonly with a coarsely striated or pitted narrow border. Through all stages, though less distinct in the oldest, the zocecial apertures are narrow and appear to be drawn out at the ends so as to connect by means of a narrow channel. This confluent character of the zocecial apertures is better shown and more regular in the central rows, where they are also narrower and on the whole considerably smaller than toward the margins. In the central rows, 10 in 5 mm. lengthwise ; 18 or 19 in 5 mm. diagonally, and five and one-half in 1 mm., and 10 in 2 mm., transversely; of longitudinal rows there are 19 or 20 in 2 mm. “ Tangential sections show that the base of the zocecia, excepting those in the marginal rows, is bounded by very thin, straight, longitudinal wall, and equally thin transverse partitions. This portion of the zocecium therefore may be described as a parallelogram, with the length and breadth respectively as four is to one. At about the middle of the hight of the primitive cell its sides have spread a little and the ends contracted in a corresponding degree. Just as the posterior half is about to be roofed over two projections from the side walls, at a. point a little behind the middle, gradually converge until they meet and thereby cut off and 15 224 SYSTEMATIC PALEONTOLOGY enclose the elliptical primitive aperture. In the succeeding stages the principal change is a reduction in the size of the apertures, caused by an internal deposit.”—Ulrich, 1893. Occurrence.—CHAMBERSBURG LIMESTONE (Caryocystites bed). Blue Spring, Franklin County, Pennsylvania. The type specimens of this species were found in the Decorah shales division of the Black Rivér at Minneapolis, Minnesota. Collections —Maryland Geological Survey, U. 8. National Museum. Genus ARTHROPORA Ulrich ARTHROPORA BIFURCATA Ulrich Plate XLVITI, Figs. 13-15 Arthropora bifurcata Ulrich, 1893, Geol. Minnesota, vol. iii, p. 178, pl. xiv, figs. 22-25, Description —“ Segments small, thin, with sharp edges and rather wide nonporiferous border, the lower ones bifurcating, usually only once; so far as observed not over 8 mm. long, and from 1.2 to 1.8 mm. wide; the upper joints shorter, their length occasionally less than 5 mm., bifurcat- ing or with a single lobe-like projection on one or both sides. Young segments with comparatively large, ovate zocecial apertures, not very regularly arranged in longitudinal and diagonally intersecting series, with about nine in 3 mm. lengthwise, and five in 1 mm. diagonally. Apertures enclosed in distinct granulose rims, connecting longitudinally. Interspaces depressed, sometimes with a few indistinct striae. With age the zocecial apertures become more circular and smaller, and the peri. stomes and connecting ridges thicker.”—Ulrich, 1893. . Occurrence —CHAMBERSBURG LIMESTONE (Christiania bed). Green- castle and other localities in southern Pennsylvania. Black River and early Trenton of Minnesota, Kentucky, Tennessee, and Canada. Collections.—Maryland Geological Survey, U. 8S. National Museum. MARYLAND GEOLOGICAL SURVEY 225 ARTHROPORA CLEAVELANDI (James) Plate LITT, Figs. 14, 15 Ptilodictya cleavelandi James, 1881, Paleontologist, No. 5, p. 38. Arthropora cleavelandi Bassler, 1906, Proc. U. S. Nat. Mus., vol. xxx, p. xiv, pl. 3, figs. 13-16; pl. 4, fig. 6. Description.—Ptilodictya cleavelandt James, as shown by the type, is founded upon segments of a rather well-marked species of Arthropora occurring abundantly throughout the various subdivisions of the Eden shale. The species is characterized by slender, generally nonbifureating segments (in consequence of which the complete zoarium must have con- sisted of comparatively only a few rigid branches) and by the numerous and small lateral branchlets springing out at nearly right angles from the main stem. The segments are usually found separated, specimens retain- ing more than a sequence of two or three being extremely rare. Ir length they vary but little from the average of Ymm. The basal seg- ment is bifurcated and drawn out acuminately below. The zocecial apertures are as usual in this genus, elliptical, surrounded by a delicate peristome. The interspaces have one or more thread-like ridges, variously disposed and with a row of minute papillae. , Occurrence.—MAarTINsBURG SitaALE (Hiden division). Pennsylvania and Maryland. Jordans Knob, one and one-half miles northeast of Fort -Loudon and Tuscarora Mountain, two and one-half miles southeast of McConnellsburg, in Pennsylvania, and the western slopes of Fairview and Rickard Mountains, Washington County, Maryland, are localities where the species may be found. A characteristic and abundant species of the Eden shale at Cincinnati, Ohio, and vicinity. Collections.—Maryland Geological Survey, U. 8. National Museum. 226 SYSTEMATIC PALEONTOLOGY Family PHYLLOPORINIDAE Genus CHASMATOPORA Eichwald CHASMATOPORA RETICULATA (Hall) Plate XL, Figs. 4-6 Intricaria ? reticulata Hall, 1847, Pal. New York, vol. i, p. 77, pl. xxvi, figs. 8a-c. Phylloporina reticulata Ulrich, 1890, Geol. Surv. Illinois, vol. viii, pp. 332, 639, pl. liii, figs. 2, 2a. Phylloporina reticulata Ulrich, 1893, Geol. Minnesota, vol. viii, p. 210, pl. iv, figs. 8-15. Chasmatopora reticulata Bassler, 1911, Bull. U. S. Nat. Mus., No. 77, pp. 170, 171, text fig. 86. Description.m“ Specimens as seen, consisting of small, flat or undulat- ing, reticulate expansions, being in each case evidently fragments of a depressed, funnel-shaped zoarium, probably not exceeding 5 cm. in diameter. Branches rounded in section, 0.2 to 0.3 mm. in diameter, inosculating at unusually frequent and regular intervals. Fenestrules somewhat elongate, about ax wide as the branches, subrhomboidai in shape in the more regularly constructed fragments; their number in a given space is fairly constant, the extremes noticed in 1 cm. being 10 and 12. Reverse of branches convex finely striated lengthwise. “ Obverse strongly convex, with three rather irregular rows of zocecia, their apertures subcircular, with a distinct peristome, about 0.1 mm. in, diameter, eight or nine in 2 mm. Acanthopores abundant, irregularly distributed, rather large, especially so in the earliest forms of the species. Interspaces slightly concave, occasionally faintly pitted and striated. “In tangential sections the zocecia are rather short, with a row on each side directed obliquely outward, and one series between them. The latter are wedge-shaped, and in deep sections appear as a more or less narrow central space. Diaphragms, one in each tube, have been observed.” Ulrich, 1893. Occurrence.—CHAMBERSBURG LIMESTONE (Caryocystites bed). Fort Loudon and Blue Spring, Franklin County, Pennsylvania. The original types are from the Trenton limestone of New York, but the species has a wide distribution in both the Black River and Trenton rocks. Collections.—Maryland Geological Survey, U. S. National Museum. MARYLAND GEOLOGICAL SURVEY 227 CHASMATOPORA SUBLAXA (Ulrich) Plate XL, Figs. 7-10 Phylloporina sublaxa Ulrich, 1890, Journ. Cincinnati Soc. Nat. Hist., vol. xii, p. 179, fig. 6. Phylloporina sublaxa Ulrich, 1893, Geol. Minnesota, vol. iii, p. 209, pl. iv, figs. 1-7. Description.—* Zoarium an undulating flabelliform expansion, attain- ing a diameter of 5 cm. or more, consisting of irregularly inosculating slender subcylindrical branches, varying in width from 0.3 to 0.6 mm., but averaging about 0.45 mm. Fenestrules large, subacutely elliptical, varying considerably in shape and size, generally two or three times longer than wide; measuring longitudinally, the average number in 1 cm is between five and six; transversely, nine or ten in the same space. These measurements apply to the Tennessee specimens. In the Minnesota form of this species the fenestrules are smaller, averaging between six and seven in 1 cm. lengthwise. “ Reverse of the Tennessee specimens strongly rounded, nearly smooth, or with faint longitudinal striae. In very young examples the latter would probably be more distinct.”—Ulrich, 1893. Occurrence. CHAMBERSBURG LIMESTONE (Caryocystites bed). Fort . Loudon and Blue Spring, Franklin County, Pennsylvania. Specimens from the Stones River, Black River, and Chazyan rocks have been identified with the types of this species which were found in the Upper Stones River limestone of Central Tennessee. Collections —Maryland Geological Survey, U. S. National Museum. Family ARTHROSTYLIDAE Genus HELOPORA Hall HELOPORA DIVARICATA Ulrich Plate XL, Figs. 1-3 Helopora divaricata Ulrich, 1886, Fourteenth Ann. Rept. Geol. Surv. Min- nesota, p. 59. Helopora divaricata Ulrich, 1898, Geol. Minnesota, vol. iii, p. 191, pl. iii, figs. 1-3. Helopora divaricata Bassler, 1911, Bull. U. S. Nat. Mus., No. 77, pp. 149-150, text fig. 72. 228 SYSTEMATIC PALEONTOLOGY Description.—“ Zoarium jointed ; segments about 7.0 mm. long, obtuse at both extremities, subcylindrical, polygonal in cross-section, the number of the angles and corresponding rows of zocecial apertures six, seven or eight. Their diameter varies with age and according to the number of zocecia contained from 0.5 to 0.9 mm. Zoccial apertures comparatively large, oblique, ovate, seeming to widen anteriorly, arranged in troughs between strong longitudinal ridges, 12 in 5 mm. lengthwise and generally in regular transverse rows. Posterior border of apertures thick, promi- nent, sloping backward into the aperture next below. This border is continued upon the sides of the zowcial aperture as two diverging ridges which extend on each side to the summit of the longitudinal keels where they meet with similar ridges from the adjoining rows. These divaricat- ing ridges cause the strong vertical keels to appear as being marked by a succession of narrow A-shaped furrows and ridges. Occasionally, and this is true more espe¢ially of the young and slender segments, the rounded posterior slope is divided by a central furrow into two small ridges.”—Ulrich, 1893. Occurrence.—CHAMBERSBURG LIMESTONE (Caryocystites bed). Fort Loudon, Franklin County, Pennsylvania. This species has heretofore been recorded from the Decorah shales of the Black River group of Minne- sota and the Kuckers shales of Esthonia, Russia. Collections.—Maryland Geological Survey, U. 8. National Museum. HELOPORA SPINIFORMIS (Ulrich) Plate XLIV, Figs. 8-10 Arthroclema spiniformis Ulrich, 1882, Jour. Cincinnati Soc. Nat. Hist., vol. v, p. 161, pl. vi, figs. 10, 10a. Helopora spiniformis Ulrich, 1893, Geol. Minnesota, vol. iii, pl. iii, figs. 4-6. Description.—“ Zoarium composed of numerous segments, which are cylindrical, poriferous on all sides, and pointed more or less obtusely at each end; their length varies from two- to four-tenths of an inch, their diameter from .015 inch to .04 inch. Cell apertures oblique, arranged between slightly elevated longitudinal lines, and in transverse rows around the stem. On account of their obliquity, well-preserved examples MARYLAND GEOLOGICAL SURVEY 229 have the lower margin of the aperture prominently elevated. There are from 8 to 16 longitudinal series of cell-apertures around the segments; seven of the transverse series occupy the space of .1 inch. Longitudinal sections show that the cells radiate from a central axis, that their walls are thin near the axis, and become much thickened as they approach the surface. No diaphragms. In transverse sections the cells radiate from the central axis, and appear as so many wedges arranged around a central point.”—Ulrich, 18938. Occurrence.—CHAMBERSBURG LIMESTONE (Echinospherites bed). Pinesburg Station, Maryland. Lebanon limestone division of the Stones River group at Lebanon and other localities in Central Tennessee. Collections —Maryland Geological Survey, U. S. National Museum. Family RHINIDICTYONIDAE Genus RHINIDICTYA Ulrich RHINIDICTYA NEGLECTA Ulrich Plate XLIV, Figs. 11-14 Stictopora paupera (in part) Ulrich, 1886, Fourteenth Ann. Rept. Geol. Nat. Hist. Surv. Minnesota, p. 69. Rhinidictya neglecta Ulrich, 1893, Geol. Minnesota, vol. iii, p. 130, pl. v, figs. 22-25. Description.—* Zoarium small, branches dividing dichotomously at intervals of from + to 7 mm., rather convex, the margins parallel, not very sharp, and with non-celluliferous border variable. Width of branches rather constant at about 1.5 mm. Zoccia in 8 to 11 ranges, the usual number nine, with rather small, elliptical, oblique apertures, about 17 in 5 mm. lengthwise, and six in 1-mm. transversely. In most cases all the apertures are directed longitudinally or parallel with the edges of the branches; in others, however, those forming the marginal row on each side may be turned slightly outward. Interspaces comparatively thick, less ridge-shaped than usual, often slightly zigzag, with the range of granules well developed. “ Internal structure chiefly diagnostic in vertical sections. These show that the primitive or prostrate cell is comparatively elongate, and that at 230 SYSTEMATIC PALEONTOLOGY the turn into the ‘ vestibule’ the wall is merely sharply curved and not angular, as in R. mutabilis.’—Ulrich, 1893. Occurrence—CHAMBERSBURG LIMESTONE (Echinospherites bed). Southern Pennsylvania and Pinesburg Station, Maryland. Lower Tren- ton of Kentucky, Tennessee, and Minnesota. Collections—Maryland Geological Survey, U. 8. National Museum. BRACHIOPODA Order ATREMATA Family OBOLIDAE Genus LINGULELLA Salter LINGULELLA sp. Description.—No fossils have been found in the Waynesboro formation in Maryland, but Stose records the discovery of a few poorly preserved shells in the sandy shales at the top, just each of Waynesboro in Pennsyl- vania. These were identified as an undetermined species of Lingulella suggesting Middle Cambrian age. Better preserved material is necessary before any stratigraphic use can be made of this species, and for that reason it has not been figured. Occurrence.—WAYNESBORO FoRMATION. Just east of Waynesboro, Pennsylvania. Collection.—U. 8S. National Museum. Genus LEPTOBOLUS Hall LEPTOBOLUS ? OVALIS 0. sp. Plate XLIX, Figs. 14-16 Description.—This interesting little brachiopod is associated with the quite similar Lingula riciniformis Hall from which it can be distin- guished externally by its more rounded beak. Internally the valves of this new Leptobolus show the two or three diverging, slightly elevated septa characteristic of the genus, but these are so faintly developed that MARYLAND GEOLOGICAL SURVEY 231 the species cannot be considered typical. Paterula, which differs from Leptobolus in having the inner margins of the valves thickened, must also be considered in determinating its final generic position. Compared with other species of Leptobolus, L. ovalis is distinguished at once by its larger size, more elongated, oval shape, more rounded beak and less clearly marked interior. Occurrence.—MARTINSBURG SHALE (Sinuites bed). Many localities in the Chambersburg and Mercersburg quadrangles of Pennsylvania and in the southern extension of the same strata into Maryland. The figured specimens are from the locality two miles northeast of Kauffman, Penn- sylvania. Collecttions—Maryland Geological Survey, U. 8. National Museum. LEPTOBOLUS INSIGNIS Hall Plate LI, Fig. 13 Leptobolus insignis Hall, 1871, Fossils from Hudson River Group, p. 3, pl. iii, fig. 17 (Twenty-fourth Rept. New York State Cab. Nat. Hist., p. 227, pl. vii, fig. 17). Leptobolus insignis Hall and Clarke, 1892, Pal. New York, vol. viii, pt. i, p. 74, pl. iii, figs. 1-6. Description.—Shell semiphosphatic, minute, 1.50-2.00 mm. in length, fragile, orbicular, with a scarcely pointed beak. Valves subcircular, regularly convex and marked with concentric lines of growth on the exterior surface. Ventral valve with a distinct pedicle groove and an elevated subquadrate muscular area on its interior. The dorsal valve is somewhat thickened on the cardinal margin and bears slightly elevated, trifid muscular impressions. The internal surface with radiating striae separates this species from other forms of the genus. Occurrence.—MARTINSBURG SHALE (Corynoides bed). Chambers- burg, Pennsylvania, and Williamsport, Maryland. Utica shale of New York, Canada, and the Ohio Valley. Collections.—Maryland Geological Survey, U. 8. National Museum. 232 SYSTEMATIC PALEONTOLOGY Family LINGULIDAE Genus LINGULA Bruguiere LINGULA RICINIFORMIS Hall Plate L, Figs. 6-8 Lingula riciniformis Hall, 1847, Pal. New York, vol. i, p. 95, pl. xxx, fig. 2. Lingula (Glossina) riciniformis Hall and Clarke, 1892, Pal. New York, vol. viii, pt. i, pl. i, fig: 3. Lingula riciniformis Winchell and Schuchert, 1893, Minnesota Geol. Surv. pt. iii, p. 343, fig. 24; pl. xxix, fig. 9. : Lingula riciniformis Weller, 1903, Geol. Surv. New Jersey, Pal. 3, p. 144, pl. ix, fig. 8. Description.—Shell oval to subelliptical in outline with the two valves equally convex; an average specimen is 8 mm. long and 4 mm. wide. Anterior margin regularly rounded, lateral margins slightly convex, sub- parallel; postero-lateral margins rounded and apex rather blunt. Sur face nearly smooth or marked by very fine concentric lines of growth Fine radiating striae are sometimes visible. As pointed out by Winchell and Schuchert in 1893 this shell is of particular interest in showing the three stages of development very clearly. The first shelled condition or “ protegulum” is very small; second comes a sharply defined circular stage, termed the Obolella stage, distinguished furthermore by its lighter color, and third arises the stage in which the shell begins to assume its specific form. Through the addition of shell substance posterior to the protegulum the apex at maturity is no longer marginal as in the Obolella stage, but has become submarginate. Occurrence.—MartInsBurG SHALE (Sinutes bed). Chambersburg, Pennsylvania, and Strasburg, Virginia. Trenton limestone of New York, Canada, Minnesota, and New Jersey. Collections.—Maryland Geological Survey, U. 8S. National Museum. LiInGULA NICKLESI n. sp. Plate LVIT, Figs. 1-3 Description.—The sandstones of Lower Maysville age in the Appa- lachiaus contain specimens of a Lingula which upon close comparison prove to be identical with a species from the upper part of the Fairview MaryLanp GEOLOGICAL SURVEY 233 division of the Maysville at Cincinnati, Ohio, and vicinity. This species has the subquadrangular outline of Lingula elderi Whitfield from the Black River group of Minnesota and Wisconsin, but its anterior end is more drawn out. It is also closely related to L. rectilateralis Emmons from the Utica shales of New York, but lacks the fine radiating striae of that species, is more elongate and less quadrate. Occurrence. —MarvINsBURG SHALE (Orthorhynchula bed at the top of the Fairview division). Head of Raver’s Run, three and one-half miles southwest of Saxton, Pennsylvania. The figured specimens are from the upper part of the Fairview forma- tion at Cincinnati, Ohio. Collection.—U. S. National Museum. Order NEOTREMATA Family OBOLELLIDAE Cenus OBOLELLA Billings OBOLELLA MINOR (Walcott) Plate XXV, Figs. 1-4 Camarella minor Walcott, 1890, Proc. U. S. Nat. Mus. for 1889, vol. 12, pp. 36-37. ; Camarella ? minor Walcott, 1891, Tenth Ann. Rept. U. S. Geol. Survey, p. 614, pl. Ixxii, figs. 4, 4a-d. * Camarella minor Hall and Clarke, 1894, Nat. Hist. New York, Paleontology, vol. 8, pt. 2, p. 221. Obolella minor Clark and Mathews, 1906, Maryland Geol. Survey, vol. 6, pt. 1, p. 252, pl. xvi, figs. 13 and 14. Description —* General form ovate, biconvex. Surface smooth or marked by concentric lines and varices of growth. Ventral valve suba- cuminate, moderately convex, with the most elevated portion at the umbo, which curves toward the small apex; the posterior or nmbonal third of the valve is usually more or less tumid, a ridge of growth separating it from the anterior portion of the shell; area nearly on the plane of the margins of the valve and divided midway by narrow, deep, pedicle furrow; casts of the interior show that the area formed a shelf on each side of the pedicle furrow. Dorsal valve transversely ovate; a narrow, short area and a slight median ridge are indicated on a cast of the interior. 234 SyYsTEMATIC PALEONTOLOGY ~ “This shell is small. A large ventral valve measures, length 7 mm.; width, 6 mm.; a dorsal valve, length 6 mm.; width, 6.5 mm.”—Walecott. Occurrence—ANTIETAM SANDSTONE. Mouth of Little Antietam Creek near Eakles Mills, one mile east-southeast of Smithsburg and other localities in Washington County, Maryland. Collections.—Maryland Geological Survey, U. S. National Museum. Family DISCINIDAE Genus ORBICULOIDEA D’Orbigny ORBICULOIDEA LAMELLOSA (Hall) Plate XLVIII, Fig. 12 Orbicula lamellosa Hall, 1847, Pal. New York, vol. i, p. 99, pl. xxx, fig. 10 (not Broderip, 1833). Orbiculoidea lamellosa Hall and Clarku, 1892, Pal. New York, vol. viii, pt. 1, pl. 4H, fig. 12. Orbiculoidea lamellosa Weller, 1903, Geol. Surv. New. Jersey, Pal., vol. iii, p. 147, pl. ix, figs. 1, 2. Description.—< Shell depressed-conical, nearly circular in outline, the apex of the brachial valve situated about one-third of the breadth of the shell from the margin. Surface marked by rather irregular, elevated, more or less lamellose, concentric lines, the grooves between the lines being rather wider than the ridges themselves. “The dimensions of a nearly perfect brachial valve are: Length, 9.5 mm.; width, 8.75 mm.; convexity, 2.5 mm.”—Weller, 1903. Occurrence—_CHAMBERSBURG LimMEsTOoNE (Christiania bed). Penn- sylvania and Virginia. Trenton limestone of Middleville, etc., New York, New Jersey, and Ontario. Collection.—U. 8. National Museum. Family ACROTRETIDAE Genus CONOTRETA Walcott CoNOTRETA RUSTI Walcott Plate L, Figs. 1-5 Conotreta rusti Walcott, 1890, Proc. U. S. Nat. Mus., vol. xii, p. 365, figs. 1-4. Conotreta rusti Hall and Clarke, 1892, Pal. New York, vol. viii, pt. i, p. 104, pl. 4K, figs. 16-21. MARYLAND GEOLOGICAL SURVEY 235 Description.—Shell small, calcareo-corneous, circular in outline and cone-shaped in form; 2 to 3mm. in height. Pedicle valve conical with the height greater than the length. Apex usually broken, but showing evi- dence of the external opening of the sipho. Extending from the apex to the posterior margin is a shallow furrow increasing in width downward. The posterior wall of the shell conforms to the curvature of the rest of the surface in small specimens, but this area becomes distinctly flattened in larger examples, as in Acrotreta. “Surface covered with sharp con- centric striae curving slightly upward as they cross the foraminal groove. In casts of the interior a strong apical callosity marking the probable position of the foramen is produced anteriorly into a short, sharp ridge, on either side of which lie two other ridges, with evidence of a third on the lateral slopes. The highly conical form of this calcareo-corneous shell and the numer- ous radiating ridges on the ventral interior readily distinguish this ‘interesting brachiopod. Occurrence.—MaRTINSBURG SHALE (Sinuites bed). Chambersburg, Pennsylvania, and Strasburg, Virginia. Trenton limestone, Trenton Falls, New York. Collection.—U. S. National Museum. Family TREMATIDAE Genus SGHIZOGRANIA Hall and Whitfield ScHIZOCRANIA FILOSA (Hall) Plate LII, Figs. 8, 9 Orbicula ? filosa Hall, 1847, Pal. New York, vol. i, p. 99, pl. xxx, fig. 9. Schizocrania filosa Hall and Whitfield, 1875, Pal. Ohio, vol. ii, p. 73, pl. i, figs. 12-15. Schizocrania filosa Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 146, pl. ix, figs. 3, 4. Description.—< Shell orbicular or subovate, the beak of the free or brachial valve projecting slightly beyond the limits of the circle, giving a somewhat greater diameter along the median line than in a transverse direction. Pedicle or attached valve discoid, very thin, deeply and broadly 236 SYSTEMATIC PALEONTOLOGY notched on the posterior side; the notch occupying nearly one-quarter of the circumference of the valve on the outer margin and extending nearly to the center of the valve, its border thickened, especially at the base, which is rounded, with the center marked by a slightly projecting point, marked by strong, irregular, concentric undulations parallel to the margin, but interrupted by the border of the notch. Brachial or free valve moderately convex, most prominent near the center, its surface marked by fine, even, thread-like, radiating striae, which increase both bv bifurcation and intercalation, and become stronger toward the border of the shell.”—Weller, 1903. This interesting brachiopod ranges in age from the Trenton to the Richmond, the best localities, however, being in the Trenton of New York and the Maysville of the Ohio Valley. In the Cumberland Valley the species is known only in the lower part (Corynoides bed) of the Martins- burg shale. Occurrence.—MARTINSBURG SHALE (Corynoides bed). Williamsport, Maryland. Collections.—Maryland Geological Survey, U. 8. National Museum. Family CRANIIDAE Genus PHOLIDOPS Hall PHOLIDOPS CINCINNATIENSIS Hall Plate LIV, Figs. 23, 24 Pholidops cincinnatiensis Hall, 1872, 24th Rept. New York State Cab. Nat. Hist., pl. vii, fig. 10. Pholidops cincinnatiensis Meek, 1873, Pal. Ohio, vol. i, p. 130, pl. v, fig. 2. Description.— Shell small, ovate in outline. Larger valve about onc- fifth longer than wide, with height one-third to one-fourth the breadth. Apex obtuse, near half way between the middle and the larger end. Anterior end narrowly rounded, posterior end somewhat more broadly rounded, or almost sub-truncate. Surface ornamented by six or seven sub-imbricating marks of growth. Smaller valve unknown. “ Length, 0.14 inch, 0.12 inch; height of larger valve, 0.04 inch.”— Meek, 1873. Manrytanp GroLogicaL SURVEY 237 Occurrence —ManrtINsBuRG SHALB (Eden division). Molds and casts showing the specific characters quite plainly are found at Jordans Knob one and one-half miles northeast of Fort Loudon, Cowans Gap, five miles northeast McConnellsburg, and Tuscarora Mountain two and one-half miles southeast McConnellsburg, Pennsylvania. In Maryland the same horizon on Rickard Mountain, Washington County, has afforded specimens. Not uncommon in the Eden and Maysville strata of the Ohio Valley. Collections.—Maryland Geological Survey, U. 8. National Museum. Order PROTREMATA Superfamily ORTHACEA Family BILLINGSELLIDAE Genus EOORTHIS Walcott EoorTHIS DESMOPLEURA (Meek) Plate XXVII, Figs. 1-5 Orthis desmopleura Meek, 1872, Hayden’s U. S. Geol. Surv. Wyoming, p. 295. Orthis (Plectorthis) desmopleura Walcott, 1905, Proc. U. S. Nat. Mus., vol. xxviii, p. 261. Eoorthis desmopleura Walcott, 1912, Mon. U.S. Geol. Surv., vol. li, p. 777, pl. xevi, figs. 1, la-r. Description.—“ This shell has the general form and external characters of FE. wichitaensis (Walcott). It differs in being less convex and in the details of the radiating ribs. Hoorthis desmopleura differs from EH. rem- nicha (N. H. Winchell) in its uniformly smaller size, less convexity, and in the details of the radiating ribs. The ribs have a wide range of varia- tion, but when from the same character of matrix they are all of the same type and the shells grade from one to the other. The ventral valves of young shells 2 to 3 mm. long are highly convex and usually appear to be a little longer than wide; if in such shells the surface striae are in sharply elevated fasiculae, the result is to all appearances a rhynchonelloid shell. 238 SYSTEMATIC PALEONTOLOGY “The interior of the ventral valve shows a narrow area, broad delthy- rium, spondylium almost free from the bottom of the valve, and a median septum that may have supported the front end of the spondyhium. In young and strongly convex shells the spondylium is narrow and very strongly defined. The narrow area of the dorsal valve is divided by a broad delthyrium, in the center of which is a very slightly developed cardinal process.”—Walcott, 1912. Occurrence.—CONOCOCHEAGUE LIMESTONE. Near Scotland, Franklin County, Pennsylvania, and the same horizon near Funkstown, Maryland, furnish fragments apparently of this species. Upper Canadian and lowest Ordovician of Utah, New Mexico and Colorado. Collections.—Maryland Geological Survey, U. S. National Museum. Family ORTHIDAE Genus HEBERTELLA Hall and Clarke TTEBERTELLA BOREALIS (Billings) Plate NNXVIII, Figs. 9-12; Plate NLI, Fig. i7 Orthis borealis Billings, 1859, Canadian Nat. Geol., vol. iv, p. 436, fig. 14. Orthis borealis Billings, 1863, Geol. Canada, p. 129, fig. 56, p. 167, fig. 148. Hebertella borealis Raymond, 1911, Ann. Carnegie Mus., vol. vii, No. 2, p. 241, text figs. 13, 14. Description Shell transversely oval, width at hinge considerably less than the width below. Sides rounded, front straight or slightly rounded. There is a low, broad depression in both valves. The pedicle valve is the more convex of the two in young specimens, but in mature shells the brachial valve is slightly the larger. The cardinal area of the pedicle valve is high and incurved, with a narrow delthyrium. The sur- face is marked by from 20 to 30 broad, simple plications, separated by very narrow grooves.”—Raymond, 1911. Occurrence-—Stones River Limestone (Middle division). Near Maugansville, Maryland; Chambersburg, Pennsylvania. CHAMBERSBURG LIMESTONE (Caryocystites bed). Fort Loudon and Blue Spring, Pennsylvania. A not uncommon Chazyan fossil in Canada and New York. In east Tennessee the species occurs in the Lenoir °( Middle Chazyan) limestone. Collections.—Maryland Geological Survey, U. S. National Museum. MARYLAND GEOLOGICAL SURVEY 239 HEBERTELLA VULGARIS Raymond Plate XX XVIII, Figs. 1-5; Plate XLI, Fig. 18 Hebertella vulgaris Raymond, 1911, Ann. Carnegie Mus., vol. vii, No. 2, p. 242, pl. xxxvi, figs. 2-5, text figs. 15-18, 22. Description. Valves nearly equally convex, outline transversely oval, hinge of variable length, but always less than the greatest width. Sides and front rounded. Some specimens have a broad shallow sinus in the pedicle valve, while others have that valve evenly convex, or merely flattened toward the front. The brachial valve usually shows a narrow but not deep sinus, which extends from the beak nearly or quite to the front. The line in which the two valves meet is usually straight, but in those specimens which have a sinus in the pedicle valve and not in the brachial, the front is sinuate. Mature specimens usually have from 60 to 90 fine striae on each valve. The striae increase both by bifurcation and implantation. The cardinal area of the pedicle valve is high and slightly incurved, the delthyrium apparently open. The teeth are supported by thin lamellae, between which are the scars of the muscles. In the brachial valve there is a low median septum which expands at the posterior end, forming a platform, in the middle of which is the small linear cardinal process. In front of this platform are two pairs of deep adductor scars. The dental sockets are narrow and deep.”—Raymond, 1911. Occurrence—StTones River LIMESTONE (Middle division). Cham- bersburg, Pennsylvania. CHAMBERSEURG LIMESTONE (Caryocystites bed). Fort Loudon and near Blue Spring, Pennsylvania. An abundant fossil in the Chazyan rocks of New York, Canada, and Tennessee. Collections.—Maryland Geological Survey, U. 8. National Museum. HEBERTELLA BELLARUGOSA (Conrad) Plate XLI, Fig. 6; Plate XLV, Figs. 10-12 Orthis bellarugosa Conrad, 18438, Proc. Acad. Nat. Sci., Phila., vol. i, p. 333. Orthis bellarugosa Hall, 1847, Pal., New York, vol. i, p. 118, pl. xxxii, fig. 3. Orthis (Hebertella ?) bellarugosa Winchell and Schuchert, 1893, Geol. Min- nesota, vol. ili, p. 434, pl. xxxiii, figs. 1-4. Hevertella bellarugosa Raymond, 1911, Ann. Carnegie Mus., vol. vii, No. 2, p. 245, pl. xxxvi, figs. 8, 9, text figs. 19, 20. 16 240 SYSTEMATIC PALEONTOLOGY Description.— Shell usually nearly circular in outline, valves about equally convex. Surface marked by from 30 to 40 coarse striae which increase by implantation and bifurcation. The radial striae are crossed by sharp concentric lamellae, producing the rugose appearance which suggested the specific name. From 10 to 15 of the radial striae are stronger than the others, and between each pair of strong striae is a single weaker one, except in the sinus of the brachial valve, where there are two. The pedicle valve is evenly convex, somewhat flattened toward the front, but without a sinus.. Hinge line less than the greatest width. Cardinal area not high, nor much incurved. The bachial valve has a narrow median sinus. “The shells vary in outline ; some are wider than long, while in others the width and length are about equal. The sides are rounded, and the front is nearly straight in some speciméns and rounded in others.”— Raymond, 1911. Occurrence—CHAMBERSBURG Limestone (Caryocystites and Echino spherites beds). Pinesburg and Wilson, Maryland; Fort Loudon and Blue Spring, Pennsylvania. The original types of this wide-spread species were obtained in the Black River rocks of Wisconsin. Collections.—Maryland Geological Survey, U. S. National Museum. Genus ORTHIS Dalman ORTHIS TRICENARIA Conrad Plate XLVII, Figs. 4-6 Orthis tricenaria Conrad, 1843, Proc. Acad. Nat. Sci. Philadelphia, vol. i, p. 333. Orthis tricenaria Hall, 1847, Pal. New York, vol. i, p. 121, pl. xxxii, fig. 8. Orthis tricenaria Hall and Clarke, 1892, Pal. New York, vol. viii, pt. 1, pp. 191, 193, 221, 228, pl. v, figs. 9-14. Orthis tricenaria Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 151, pl. ix, figs. 18-21. Description.—“ Shell plano-convex, longitudinally semi-elliptical in outline ; hinge-line equal to the greatest width of the shell, rarely shorter. Cardinal area well developed on each valve. Surface marked by 30 to 36 MaryLanp GEOLOGICAL SURVEY 241 usually nearly equal, simple, subangular, radiating costae, which are crossed by exceedingly delicete, concentric lines of growth. Pedicle valve strongly convex, subangular along the median line, with the greatest elevation on the umbo. Cardinal area very high, more or less concave, striated longitudinally and transversely, divided by a very narrow delthy- rium, whose apical third is occupied by a flat, concave or convex deltidium. Brachial valve nearly flat, slightly elevated at the beak, from which point the surface slopes gradually into a broad, scarcely perceptible, rarely well- defined, median sinus. Cardinal area nearly one-third as wide as that of the pedicle valve, flat, divided by a triangular delthyrium, which is as broad as long and more or less covered by a convex chilidium, the anterior margin of which is concave. The dimensions of a rather large specimen are: Length, 19 mm.; width, 20 mm.; thickness, 10.5 mm.”—Weller, 1903. | A characteristic fossil of the Black River group of the Mississippi and Appalachian valleys. Occurrence.—CHAMBERSBURG LimesToNE (Nidulites bed). Wilson and Pinesburg, Maryland. Collections.—Maryland Geological Survey, U. 8S. National Museum. Genus PLECTORTHIS Hall and Clarke PLECTORTHIS PLICATELLA Hall Plate LVII, Figs. 4-7 Orthis plicatella Hall, 1847, Pal. New York, vol. i, p. 122, pl. xxxii, fig. 9. Orthis plicatella Meek, 1873, Pal. Ohio, vol. i, p. 108, pl. viii, fig. 7. Plectorthis plicatella Hall and Clarke, 1892, Pal. New York, vol. viii, pt. i, p. 22, pl. v, figs. 18-20. Description.— Broadly semioval, nearly equivalve, length and breadth about as 3 to 4; surface marked by strong radiating plicae, which are usually simple, about 20 to 28 on each valve, crossed by simple elevated concentric lines, which are more distinct in the depressions between the costae, and often obscure or obsolete upon their exposed surfaces; valves nearly equally convex, without sensible depression or elevation on either one, meeting at the edges in a straight line; cardinal line not extending 242 SYSTEMATIC PALEONTOLOGY beyond the width of the shell; area narrow, dorsal foramen extending to the beak.”—Hall, 1847. Occurrence—MartiInsBuRrG SHALE (Orthorhynchula bed at the top of the Fairview division). Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Pennsylvania. The types of this species were obtained in the upper part of the Fairview formation at Cincinnati, Ohio. Collections.—Maryland Geological Survey, U. 8S. National Museum. PLECTORTHIS PLICATELLA Hall var. Plate LIV, Figs. 15-16 Description.—The typical form of this species occurs in the lower part of the Maysville group at Cincinnati, Ohio, and vicinity. The upper part of the Martinsburg shale in Pennsylvania has afforded brachiopod so close to P. plicatella that it cannot be considered more than a variety. Unfortunately the preservation of these specimens is not good enough to allow this variety to be distinguished. A description of Plectorthis plicatella is given above. Occurrence.—MARTINSBURG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania, has fur- nished the Eden form here regarded as a variety. Collections.—Maryland Geological Survey, U. 8. National Museum. Genus DALMANELLA Hall and Clarke DALMANELLA TESTUDINARIA (Dalman) var. Plate L, Figs. 9, 10 Orthis testudinaria Dalman, 1828, Kong]. Svenska Vet.-Akad. Handl., p. 115, pl. ii, fig. 4. Fi Dalmanella testudinaria Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 155, pl. x, figs. 1, 2; p. 216, pl. xvi, figs. 4, 5. Description.—* Adult shells subcircular and the younger’ ones trans- versely subelliptical in outline; hinge-line less than the greatest width; cardinal angles rounded, lateral and anterior margins broadly rounded, though the extreme front of the shell is sometimes straight for a short MaryLAND GEoLogicaL SURVEY 243 distance, Surface of both valves marked by unequal, angular, radiating costae, about 10 or 12 of the largest ones having their origin at the beak, the remainder being lateral branches from these. In some of the larger individuals as many as 60 or more costae are present along the margin of the shell. The branches from the main costae are small at first, but increase in size towards the margin of the shell, and themselves give off additional branches. In many individuals this manner of branching gives, to the costae a more or less fasciculate appearance, each fascicle having one large rib in the center, with smaller ones on either side. In those specimens having the shell well preserved the bottoms of the grooves between the costae exhibit a series of fine, transverse crenulations. Pedicle valve convex, subcarinate along the median line, the lateral slopes nearly straight, the greatest convexity of the valve about one-third the distance from the beak. Cardinal area moderately concave, forming an angle of about 45° with the plane of the valve, about five or six times as high. Delthyrium a little higher than wide. Brachial valve nearly flat, with a sinus beginning close to the beak and expanding in a broad, shallow depression towards the front. “The dimensicns of an average-sized specimen are: Length, 8 mm.; width, 8.25 mm.; convexity of pedicle valve, 2.5 mm.”—Weller, 1903. The particular variety of Dalmanella testudinaria described above by Weller from the Trenton limestone of New Jersey is represented in the Sinuites bed at the base of the Martinsburg shale. Occurrence.—Marrinspurc SHALE (Sinuites bed). The Trenton variety here figured occurs at Chambersburg, Pennsylvania, and Stras- burg, Virginia. Shells identified as this species occurs in most of the Middle and Upper Ordovician strata of Kurope and America. Collections —Maryland Geological Survey, U. S. National Museum. DALMANELLA EDSONI 0. sp. Plate XLIX, Figs. 17-21 Description —This well-marked new species is distinguished by its large size and by its sharply folded plications, arranged in bundles. The length and breadth of average specimens from southern Pennsylvania is 244 SYSTEMATIC PALEONTOLOGY as 3 is to 4 mm., that is, the length is 18 mm. and the breadth 24 mm. Other specimens from the same area attain as great a breadth as 35 mm. The Vermont specimens are even more robust, an average specimen here being 80 mm. long and almost 40 mm. broad. The arrangement of the plications in bundles, each bundle being marked off by a stronger plica- tion, is also a striking specific feature. The specific name is in honor of the late George E. Edson, who discovered the species in the Trenton rocks of Vermont. Occurrence.—MartinsBurG SHALE (Sinuites bed). Two miles south of St. Thomas, Pennsylvania. Lower Trenton at Highgate Springs, Ver- mont. Collection.—U. 8. National Museum. DALMANELLA MULTISECTA (Meek) Plate LIV, Figs. 5, 6 Orthis emacerata var. multisecta (James MSS.) Meek, 1873, Pal. Ohio, vol. i, p. 112, pl. viii, fig. 3. Orthis emacerata var. multisecta Miller, 1875, Cincinnati Quart. Jour. Sci., vol. ii, p. 22. Orthis multisecta Sardeson, 1897, American Geologist, vol. xix, p. 97, pl. iv, figs. 20-23. ; Dalmanella testudinaria var. multisecta Cumings, 1908, 32d Ann. Rept. Dept. Geol. and Nat. Res. Indiana, p. 901, pl. xxxiii, figs. 4, 4c. Description.—* Shell small, subcircular, plano-convex, or sometimes concavo-convex, hinge line shorter than the greatest breadth of the valves ; valves thin. Dorsal valve nearly flat, or having a concentric depression through the middle; mesial sinus undefined or indistinct; beak, small, not incurved ; area low at the middle, and narrowing off to nothing at the lateral extremities; foramen very small and filled by the cardinal process. Interior flat; mesial ridge extending to about the middle of the shell, without any well-defined termination; scars of posterior pair of adductor muscles a little smaller than the anterior pair, from which they are separated by a very fine line, or, more generally, not distinctly sepa- rated; cardinal process very small, conical, obscurely trifid on the pos- * MaryYLAND GEOLOGICAL SURVEY 245 terior side; brachial processes slender, prominent, and directed obliquely forward ; surface granular and showing the radiating striae. * Ventral valve convex, with elevated mesial ridge, greatest convexity just behind the middle; beak arched, projecting slightly; area moderate, narrowing laterally; foramen an equilateral triangle, partly occupied by the cardinal process of the other valve. Interior strongly concave, show- ing moderately prominent teeth; dental laminae extend from the base of the teeth forward, gradually becoming more indistinct as they fade away in a circular line to the mesial depression, forming a heart-shaped cavity for the muscular scars; surface granular and showing the radiating striae. “Surface of both valves ornamented by fine radiating striae, that increase by bifurcation; lateral striae curved so that a few of them run out on the hinge line; concentric striae plainly visible with the aid of a magnifier, and sometimes visible to the unaided eye; imbricating marks of growth usual. Length of an average full-grown specimen, 0.50 inch; breadth, 0.58 inch; convexity, 0.20 inch. They vary, however, from one- fourth this size to one-half larger.”—Miller, 1875. This is probably the most abundant fossil of the Eden shale wherever exposed. In the Appalachian Valley of Pennsylvania and Maryland it occurs in the upper sandy layers of the Martinsburg. Occurrence.—MarTINSBURG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, in Pennsylvania, and the west slope of Rickard Mountain in Maryland furnish specimens. Collections—Maryland Geological Survey, U. S. National Museum. DALMANELLA ELECTRA (Billings) Plate XXXV, Fig. 6 Orthis electra Billings, 1865, Pal. Foss., vol. i, p. 79, fig. 72. Dalmanella electra Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 125, pl. iv, fig. 13. Description.—Shell wider than long, the usual dimensions being about 6 mm. in length and 7 mm. in width, with the hinge-line a little shorter than the greatest width, and the cardinal extremities angular. Pedicle 246 SYSTEMATIC PALEONTOLOGY valve moderately convex on the umbo, but more flattened towards the cardinal extremities; cardinal area narrow, concave above; beak project- ing slightly beyond the cardinal margin. Surface marked by about 50 fine, subequal, radiating costae, increasing by bifurcation. The numerous fine radiating costae distinguish this shell from the closely allied Dalmanella wemplei Cleland, which differs in having larger costae at regular intervals. Occurrence—BEEKMANTOWN LimEsToNE (Ceratopea zone). West of Hagerstown, near Halfway, and east of Williamsport, Maryland. Canadian at Point Levis, Quebec, Newfoundland, New Brunswick, New Jersey and Pennsylvania. Collections —Maryland Geological Survey, U. 8. National Museum. DALMANELLA WEMPLEL Cleland Plate XX XI, Figs. 7-12 Dalmanella (Orthis) wemplei Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 129 (257), pl. xvii, figs. 10-13. / Dalmanella wemplei Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 124, pl. iv, figs. 10-12. Dalmanella wemplei Cleland, 1903, Bull. Amer. Pal., vol. iv, p. 19. Description.—Shell small, the average being about 5 mm. long and 6 mm. wide, subquadrangular to subcircular in outline, with the hinge- line slightly shorter than the width; cardinal extremities usually quite angular. Pedicle valve strongly convex, highest posterior to the middle; beak elevated, projecting beyond the hinge-line; cardinal area high, slightly arched. Brachial valve much less convex than the pedicle, with a mesial depression which may become a shallow sinus towards the front. Surface of each valve marked by from 10 to 16 stronger, radiating costae, alternating with from two to four finer ones. This species differs from the closely related Dalmanella electra (Bill- ings) which occurs in the higher beds of the Beekmantown, especially in its coarser striae which alternate with from two to four finer ones. The original types were collected in the Tribes Hill limestone at Fort Hunter, New York. The species has been identified by Weller in the MARYLAND GEOLOGICAL SURVEY 247 corresponding horizon in the Canadian part of the Kittatinny limestone at Columbia, New Jersey. Specimens fairly well preserved are not uncommon in the Stonehenge limestone, particularly the upper part, at many localities in Maryland. The outcrops around Hagerstown and Funkstown have shown some layers fairly crowded with this brachiopod. Occurrence.--BEEKMANTOWN LIMESTONE (Stonehenge member). Numerous localities in Maryland, especially around Hagerstown and Funkstown. Tribes Hill limestone at Fort Hunter, New York, and Kit- tatinny limestone, Columbia, New Jersey. Collections —Maryland Geological Survey, U. S. National Museum. Family RHIPIDOMELLIDAE Genus DINORTHIS Hall and Glarke DinortHis (PiLarsiomys) piatys (Billings) Plate XX XVIII, Figs. 6-8 Orthis platys Billings, 1859, Canadian Nat. and Geol., vol. iv, p. 438, fig. 15. Dinorthis platys Schuchert, 1897, Bull. U. S. Geol. Surv., 87, p. 216. Plaesiomys platys Raymond, 1911, Ann. Carnegie Mus., vol. vii, No. 2, p. 238, pl. xxxv, figs. 13, 14. Description.—< Pedicle valve fairly high and convex on the umbo, flat or only slightly convex in front. Brachial valve nearly flat, usually showing a shallow sinus on the umbo. Surface marked by fairly coarse striae, which increase by implantation. There are usually three or four in the space of 2 mm. on the front of the shell. The interior of the pedicle valve shows a small muscle area under the beak, composed of two strong diductor scars, and between them two very narrow adductor scars. Delthyrium narrow. No specimen has been seen which was so preserved as to retain the deltidium. In the brachial valve there is a low median septum. Other details could not be made out.”—Raymond, 1911. Occurrence-—SToNES River LimEsToNE (Middle division). Maugans- ville, Maryland. The types occurred in the Chazyan at Montreal, Canada. In the Lake Champlain area this fossil occurs in the Crown Point or middle division 248 SYSTEMATIC PALEONTOLOGY of the Chazyan. In east Tennessee it is found in the supposedly equiva- lent horizon—the Lenoir limestone. Collections.—Maryland Geological Survey, U. S. National Museum. DINORTHIS PECTINELLA (Emmons) Plate XLV, Figs. 8, 9 Orthis pectinella Emmons, 1842, Geol. New York, Rep. 2d Dist., p. 394, fig. 2. Dinorthis pectinella Hall and Clarke, 1892, Pal. New York, vol. viii, pt. 1, pp. 195, 222, 228, pl. v, figs. 27-33. Orthis (Dinorthis) pectinella Winchell and Schuchert, 1893, Geol. Minne- sota, vol. iii, p. 424, pl. xxxii, figs. 31-34. Dinorthis pectinella Weller, 1908, Geol. Surv. New Jersey, Pal., vol. iii, p. 154, pl. ix, figs. 29, 30. Description.—“ Shell resupinate, transversely subelliptical in outline, wider than long, in about the proportion of four to three; cardinal line is usually less than the greatest width of the shell, the cardinal extremities rounded; surface of each valve marked by from 22 to 30 prominent, rounded, simple costae, which are equal in width to the spaces between, and are crossed by fine, closely crowded elevated, concentric lines of growth. Pedicle valve slightly convex near the beak, flattened on the sides, with a broad, shallow, ill-defined depression along the center, usually most distinct in front, but frequently nearly obsolete. Cardinal area moderately large and well defined, flat, lying nearly at right angles to the plane of the shell. Brachial valve regularly convex, most prominent in the center, flattened and slightly deflected near the cardinal extremi- ties. Cardinal area much narrower than that of the opposite valve, lying nearly in the plane of the shell. “The dimensions of the nearly perfect pedicle valve are: Length, 21 mm.; width, 27.5 mm.”—Weller, 1903. Occurrence.—CHAMBERSBURG LimESTONE (Hchinospherites bed). Wilson and Pinesburg, Maryland. This species occurs in the Upper Black River and Early Trenton of New York and Canada, and the Ohio and Mississippi valleys. Collections—Maryland Geological Survey, U. S. National Museum. MARYLAND GEOLOGICAL SURVEY 249 Genus PIANODEMA Foerste PIANODEMA SUBAEQUATA (Conrad) Plate XLV, Figs. 1-3 Orthis subaequata Conrad, 1843, Proc. Acad. Nat. Sci. Philadelphia, vol. i, Dp. 333. Dalmanella subaequata Hall and Clarke, 1892, Pal. New York, vol. viii, pt. 1, pp. 194, 207, 224, pls. 5c, figs. 6-11. Orthis (Dalmanella) subaequata Winchell and Schuchert, 1893, Geol. Min- nesota, vol. iii, p. 446, pl. xxxiii, figs. 30-36. Dalmanella subequata Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 156, pl. x, figs. 3, 4. Description.—< Shell subequally biconvex, usually wider than long; the hinge-line shorter than the greatest width of the shell, except some- times in young individuals; cardinal extremities angular or rounded. Surface of each valve marked by numerous, fine, tubulose striae, which bifurcate about twice in passing from the beak to the anterior margin. Pedicle valve strongly and evenly convex, the greatest elevation posterior to the middle of the shell; near the beak and upon the umbo no medial depression exists, but near the middle of the valve a broad, shallow and indistinct sinus begins and becomes deeper toward the anterior margin. The cardinal area is well defined, broadly triangular, elevated and only moderately concave; the delthyrium, with slightly curved sides, is about twice as high as wide. Brachial valve more evenly, but a little less convex than the pedicle, the greatest elevation near the middle. Near the beak the mesial portion of the shell is usually flattened or slightly depressed, but near the middle of the shell this flattening gradually changes into a low, broad, ill-defined elevation, corresponding with the sinus of the pedicle valve. The cardinal area is narrow and concave, with a delthy- rium as broad or broader than high. The dimensions of an average speci- men are: Breadth, 16 mm., and length, 14 mm.”—Weller, 1903. Occurrence.—CHAMBERSBURG LimMEsTONE (LEchinospherites bed). Pinesburg Station, Maryland, and various localities in southern Penn- sylvania. Stones River group of Tennessee and the Black River group of Minnesota, etc. : Collections—Maryland Geological Survey, U. S. National Museum. 250 SYSTEMATIC PALEONTOLOGY Superfamily STROPHOMENACEA Family STROPHOMENIDAE Genus STROPHOMENA Blainville STROPHOMENA STOSEI 0. sp. Plate XXXVII, Figs. 1-4 Description.—This brachiopod, which is the most frequent fossil of the few species discovered in the Frederick limestone is known from both brachial and pedicle valves, although none show the hinge line clearly. Its general shape is that of Strophomena sinuata James of the Cincinnatian rocks, but S. stosei differs conspicuously in the occurrence of several fine radiating striae between each of the larger coarse ones. The interior of the brachial valve in each of these species seems to be quite alike and the reference of this new species of Strophomena to the S. sinuata group appears to be warranted. The specific name is in honor of George W. Stose, of the U. S. Geo- logical Survey, who helped collect the type specimens. Occurrence.—FREDERICK LIMESTONE. Just east of Frederick, Mary- land. Collections.—Maryland Geological Survey, U. 8. National Museum. STROPHOMENA SCULPTURATA 0. sp. Plate XLIX, Fig. 1 Description.—Although this new species belongs to a group of brachio- pods not uncommon in the faunas of eastern North America, all of these species happen to be new, so that comparison is not necessary. It is the only brachiopod in the Middle Ordovician limestone with such a highly sculptured shell and for that reason will be easily recognized. Between each of the very distinct radiating ridges there are five or six smaller radiating striae visible only under a lens. Transverse to these radiating striations are concentric, squamose ridges of growth quite similar to those obtaining in Leptaena charlottae. In the latter respect the group of species is related to Leptaena, but other features suggest Strophomena. An average specimen is 10 mm. high and 13 mm. wide. MarYLanp GEOLOGICAL SURVEY 251 Occurrence.—Martinspura SHALE (Sinuites bed). Pennsylvania. The type specimens are from one mile south of St. Thomas. Collections —Maryland Geological Survey, U. S. National Museum. STROPHOMENA HALLIE (S. A. Miller) Plate LIV, Figs. 7-9 Streptorhynchus ? hallie Miller, 1874, Cincinnati Quart. Jour. Sci., vol. 1, p. 148, figs. 14-16. Strophomena hallie Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, p. 38, pl. ii, figs. la-e. Description.— Shell sub-trigonal in outline, concavo-convex, deflected laterally, resupinate, rather thin and frail; hinge scarcely equalling the greatest breadth of the valves; length and breadth about three-fourths of an inch. “ Dorsal valve convex in the central part, flattened on the umbone and deflected laterally ; surface marked by moderately coarse, radiating striae, which increase by intercalation of smaller ones; area linear, beak not distinct from the edge of the area. Interior showing cardinal process to be very small and divided into two teeth-like parts, directed a little forward and flattened on their faces; socket-ridges small, short, and oblique ; mesial ridge scarcely perceptible without a magnifier, radiating striae plainly visible. “Ventral valve moderately concave in the central and anterior regions, but slightly convex at the beak, which is perforated and projects slightly beyond the edge of the area; surface marked by radiating striae, which increase by even bifurcations ; area narrow and sloping laterally ; foramen closed by a rounded deltidium for the reception of the cardinal teeth of the dorsal valve. Interior showing trigonal hinge and circular cavity; marked by radiating striae.”—Miller, 1874. Occurrence.—MarTINSBURG SHALE (Eden division). Jordans Knob one and one-half miles northeast of Fort Loudon, and Tuscarora Moun- tain, two and one-half miles southeast of McConnellsburg, Pennsylvania. Eden shale at Cincinnati, Ohio. Collection.—U. S. National Museum. 252 SYSTEMATIC PALEONTOLOGY STROPHOMENA SINUATA James Plate LIV, Figs. 10-14 Strophomena sinuata James, 1871, Cat. Fossils, Cincinnati group, p. 9. Strophomena (Hemipronites) sinuata Meek, 18738, Pal. Ohio, vol. i, p. 87, pl. 15, fig. 5a-g. Strophomena sinuata Foerste, 1912, Bull. Sci. Lab. Denison Univ., vol. xvii, p. 57, pl. i, figs. 3a-d. Description.—< Shell semicircular, or forming rather more than a semicircle, moderately convex, with valves nearly equal, the dorsal being most convex in the central and anterior regions, and the ventral near the umbo; hinge nearly or quite equalling the greatest breadth; lateral margins forming more or less nearly right angles with the hinge line; or sometimes rounding a little to the same, and rounding regularly to the front, which forms a semicircular curve, with rarely a slight sinuosity at the middle. “ Dorsal valve, flat at the beak, which is not distinct from the cardinal margin, usually a little raised in the middle at the front, so as to form a low, broad, undefined medial prominence; cardinal area narrow and inclined backward; interior with a low, small, deeply bipartite cardinal process, from which diverge three small ridges, the two lateral of which extend obliquely outward to form the margins of the rather well-defined sockets for the reception of the teeth of the other valve, while the third ridge is central, and extends a short distance forward; muscular scars not visible in any specimen examined. “Ventral valve moderately convex at the umbo, which is not very prominent or arched, and has a minute perforation at the apex; front with usually a broad, shallow, undefined depression; lateral regions more or less nearly flat; cardinal area well developed, tapering to the lateral extremities, flat, and inclined more or less obliquely backward; foramen closed by a prominent, triangular deltidium; interior showing small, somewhat saucer-shaped cavity, formed by the low, sharp dental laminae, extending forward from the inner side of the rather well-developed oblique cardinal teeth, and curving a little toward each other, without MarRYLAND GEOLOGICAL SURVEY 253 meeting at their inner ends; muscular scars not visible in any specimens examined. “ Surface of both valves ornamented with rather coarse radiating striae, most of which bifurcate once or oftener, while occasionally a shorter one is intercalated between two longer; crossing the whole, occa- sional small marks of growth, and finer but obscure, concentric striae may be seen, by the aid of a lens, on well-preserved specimens. “Length of a rather large specimen, 0.65 inch; breadth, 0.88 inch; convexity, 0.30 inch.”—Meek, 1873. Occurrence.—MartinsBurGc SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, and Tuscarora Moun- tain, two and one-half miles southeast of McConnellsburg, Pennsylvania. This species has hitherto been recorded only from the upper part of the Fairview formation in the Ohio Valley. Collections.—Maryland Geological Survey, U. S. National Museum. Genus PLECTAMBONITES Pander PLECTAMBONITES PISUM Ruedemann Plate XLVIII, Figs. 1-7 Plectambonites pisum Ruedemann, 1902, Bull. New York State Museum, No. 49, p. 19, pl. i, figs. 8-20. Description.—“ Shell small, semicircular in outline, with subauricu- late cardinal extensions ; highly concavo-convex, the convexity surpassing that of a hemisphere; toward the cardinal ears becoming depressed con- vex; length to width as 4:5; greatest width along the hinge line, which is nearly straight. Surface marked with very fine striae, which usually are interrupted by from 16 to 20 coarse striae; sometimes the fine striae become nearly obsolete, leaving the interspace between the coarse striae almost smooth; at other times the coarse striae disappear, leaving the shell uniformly and finely striated ; a few concentric growth lines are also present. Pedicle valve extremely gibbous, the greatest elevation being in the central part; the unbonal part sloping abruptly; the umbo being 254 SYSTPMATIC PALEONTOLOGY protuberant and projecting beyond the cardinal line; anterior and lateral slopes less abrupt, near the margins turning suddenly into a flatter border. Cardinal area moderately elevated, concave, delthyrium large, of equal width and length; no deltidium observed. Teeth small, supported by strong, diverging dental lamellae, which continue in outward direction into the much elevated margin of the diductor muscles; this margin extends about one-fourth the length of the valve, and then returns under an acute angle including a very deep pyriform muscle pit. The muscle margins are separated by a distinct septum, which extends to near the anterior margin; from the anterior part of the muscular impressions extend strongly marked vascular trunks which are tri- or quadripartite and inclose between them a narrow elongate depressed area. Brachial valve concave in the middle part, closely following the curvature of the pedicle valve with a well-defined ridge all around the lateral and anterior margin. Cardinal area as high as that of the pedicle valve, and also slightly concave, retrorse, with a large chilidium, somewhat concave in the middle. Cardinal process single and erect and, by the coalescence with the divergent, short, crural plates, appearing distinctly trilobate at the posterior end, similarly to P. sericeus, with the difference, however, that the posterior ends of the crural plates are not closely appressed to the cardinal process, but separate again a little, forming processes almost as ‘prominent as and parallel to the cardinal process. Adductor scars shallow, broadly triangular, extending not quite to the middle of the shell, slightly divergent, inner margins formed by two ridges, branching from the crural processes and extending to near the anterior margin ; outer somewhat indented margin of the muscular impressions greatly elevated as in P. gibbosus Winchell and Schuchert. “Dimensions: Length, 8.5 mm.; width, 10.2 mm.; height, 5.5 mm.”— Ruedemann, 1902. Occurrence—CHAMBERSBURG LimESTONE (Christiania bed). Penn- sylvania, Maryland, and Virginia. Rysedorph conglomerate at base of Trenton, New York. Collections —Maryland Geological Survey, U. 8. National Museum. MARYLAND GEOLOGICAL SURVEY 255 PLECTAMBONITES RUGOSUS (Meek) Plate LIV, Figs. 31-33 Leptaena sericea var. rugosa Meek, 1873, Pal. Ohio. vol. i, pt. 2, pl. v, figs. 3f-h. Plectambonites rugosa Foerste, 1912, Bull. Sci. Lab. Denison University, vol. xvii, p. 123, pl. i, figs. 7a-c; pl. x, figs. Ta-d. Description.—The form of Plectambonites found so abundantly in the Eden shales of the Cincinnati area was long ago separated by Meek as a variety of the ubiquitous species P. sericea. “The term rugosa was given not on account of the oblique wrinkles along the hinge-line, but on account of the roughened surface of the general exterior surface of the valves, especially anteriorly. This roughened surface appears due to the presence of numerous very thin overlapping films of shell material. These films appear to consist of the same extremely fine, silky, fibrous material as that forming the compact body of the valves. Sometimes they are traversed by the same radiating striae as those seen on that part of the exterior surface of the valves where the films are not present. The films may be more or less discrete from one another, but in some specimens they are built up into a solid mass, resulting in a thickening of the valves exteriorly. At the exterior margin of the pedicle valve, this thickening may reach a total of fully 2 mm., and frequently the anterior, more or less vertical slope of this thickening is crossed by lines evidently corre- sponding to the extensions of the radiating striae. The thickening usually is confined to the anterior half or third of the valves. It may result in a succession of concentric bands, the one nearest the anterior margin being the most conspicuous. At other times, the thickening increases evenly, without any concentric banding, but, most frequently it is more or less irregular, the films being more or less warped or broken into shreds.”—Foerste, 1912. Occurrence—MaRTINSBURG SHALE (Eden division). Jordans Knob. one and one-half miles northeast of Fort Loudon, Pennsylvania, and in the same horizon on Rickard Mountain, Maryland. Eden shale of the Ohio Valley. Collections.—Maryland Geological Survey, U. 8. National Museum. 17 256 SYSTEMATIC PALEONTOLOGY Genus CHRISTIANIA Hall and Clarke CHRISTIANIA TRENTONENSIS Ruedemann Plate XLVIII, Figs. 16-18 Christiania trentonensis Ruedemann, 1902, Bull. New York State Mus., No. 49, p. 21, pl. ii, figs. 2-6. Description —* Shell small, convexo-concave, somewhat variable in shape, rotundo-quadrate to rotundo-rectangular; sides sub-parallel or slightly converging to the cardinal line; front rounded. Hinge line straight, only slightly shorter than the greatest width of the valve in the middle part; cardinal extremities obtusely angular, having the appear- ance of flattened ears. Pedicle valve uniformly and strongly convex; umbo slightly projecting and very narrow; beak obscure. Cardinal area narrow (?); interior of pedicle valve not observed. Brachial valve strongly concave, beak hardly projecting beyond the long, straight hinge line. Cardinal extremities strongly developed, flat; area very small, cardinal process small, bipartite on its anterior face; the lobes being denticulate anteriorly with from three to five small denticles on each side. Crural plates very long and slightly divergent; the lower portion produced on each side as a strongly elevated wall with perpendicular ‘sides extending in the original direction of the crural plates close to the ante-lateral angle, where it recurves and returns, parallel to the median axis and nearly in a straight line as a still more prominent wall merging into the base of the cardinal process. The elongate, symmetric, sub- rectangular spaces thus formed are each divided transversely by a vertical ridge about one-third of the length of the valve from the cardinal line. The long narrow space between the inner muscular walls is also bounded anteriorly by a low, rounded, curving ridge and divided in the median line of the shell by a low, rounded, longitudinal ridge. The anterior half of the surface of the long anterior adductors is very rugose and radially striated. “ The surface is covered with concentric lines of growth and radiating quite widely separated, filiform striae with smooth, flat, interspaces.”— Ruedemann, 1902. MaryYLAND GEoLoGIcAL SURVEY 257 Occurrence.—CHAMBERSBURG LaimEsTonE (Christiania bed). Appa- lachian Valley of Pennsylvania, Maryland, and Virginia. Rysedorph conglomerate at base of Trenton, New York. Collections.—Maryland Geological Survey, U. 8S. National Museum. CHRISTIANIA LAMELLOSA N. sp. Plate XLIX, Figs. 3-10 Description.—The strongly lamellose surface of this brachiopod is sufficient reason for discriminating it from all other described species of the genus. The general outline of the shell is not unlike several small shells of the Chambersburg and early Trenton rocks referred to both Christiania and, Plectambonites, but the interior of the valve shows the characteristic markings of the former genus. The pedicle valve is strongly convex and bears the concentric lamellae almost to the beak. The brachial valve is as strongly concave, with a smooth surface. The average shell is 9 mm. high and about 10 mm. wide. Occurrence.—MARTINSBURG SHALE (Sinuites bed). Southern Penn- sylvania; also abundant at the same horizon in northern Virginia, the types being from Strasburg. Collections.—Maryland Geological Survey, U. 8. National Museum. Genus LEPTAENA Dalman LEPTAENA CHARLOTTAE Winchell and Schuchert Plate XLI, Figs. 11-13 Leptaena charlottae Winchell and Schuchert, 1892, Amer. Geol., vol. ix, p. 288. Leptaena charlottae Winchell and Schuchert, 1893, Geol. Minnesota, vol. iii, p. 410, pl. xxxii, figs. 1-5. Strophomena halli Sardeson, 1892, Bull. Minnesota Acad. Nat. Sci., vol. iii, p. 334, pl. iv, figs. 36, 38. Description.—* Shell small, transversely semioval, plano-convex, ge- niculate, with the sides slightly convex and converging to the broadly rounded front, or drawn out tongue shaped; hinge-line as long as, or 258 SYSTEMATIC PALEONTOLOGY somewhat shorter than, the greatest width of the shell. Surface marked by fine, closely crowded, alternating striae, as in Rafinesquina alternata, crossed by exceedingly delicate concentric lines and over the central flat disc of each valve by more or less continuous zigzag undulations or wrinkles. “Ventral valve depressed-convex over the greater portion of the shell and more or less suddenly bent downward or geniculated along the margin, especially anteriorly. Cardinal area wide, broadly triangular, with a convex deltidium, wider than long, apically perforated by a rather large pedicle opening, posteriorly excavated and completely occupied by the chilidium of the other valve. Crenulated hinge teeth prominent and supported by short dental plates, which are attached to the elevated outer margin of the small, transversely oval muscular area. Within this area, in the center of the mesial thickening, are placed the short and narrow adductors, surrounded by the large diductors, and outside these, at the base of the dental plates, are the distinct scars of the small adjustors. Surface marked by delicate, crowded papillae, strongest in front of the muscular area, and in the thin shells by the wrinkling of the outer surface. “Dorsal valve nearly flat, with the anterior margin more or less reflexed downward. Cardinal area narrow, about one-third that of the other valve, with a broad and strongly convex chilidium. Dental sockets deep; crural plates slender, very bilobed, cordate cardinal process; in front of this is a short, low septum separating the inconspicuous septa. Just inside the outer margin of the valve is situated a prominent, rounded ridge of the same nature as that in L. rhombotdalis.”—Winchell and Schuchert, 1893. Leptaena charlotiae differs conspicuously from all other American species of the genus in its zigzag, concentric surface corrugations. Occurrence-—CuamBrrspurc LIMESTONE (Caryocystites bed). Fort Loudon and Blue Spring, Franklin County, Pennsylvania. The type specimens were described from the Decorah shales division of the Black River at Minneapolis and St. Paul, Minnesota. Collections.—Maryland Geological Survey, U. 8. National Museum. ALARYLAND GEOLOGICAL SURVEY 259 LEPTAENA GIBBOSA (James) Plate LIV, Fig. 25 Strophomena gibbosa James, 1874, Cincinnati Quart. Jour. Sci., vol. i, p. 833. Leptaena gibbosa Foerste, 1909, Bull. Sci. Lab. Denison Univ., vol. xiv, . 316. peace gibbosa Foerste, 1912, Idem., vol. xvii, p. 116, pl. i, figs. 5a-e. Description.—* Shell fragile, semi-oval; cardinal line extended to or a little beyond the width of the shell farther forward, deflected at the extremities ; lateral and front margins regularly rounded. Ventral valve slightly convex in the umbonal region, but at about one-third or one-half the distance from the beak, toward the front and lateral margins, it curves suddenly upward, then rounds off, and is deflected as suddenly the other way to the front and sides, forming a high rounded ridge, giving to the shell a decidedly gibbous form; this hump extends to about 1/8th of an inch of the cardinal line on each side, where the shell is rather depressed from the umbonal slopes outwards to the deflected extremities immediately in front of the cardinal line; cardinal area linear; beak rather prominent, projecting, minutely perforated; six to eight slight wrinkles on the umbonal region. Surface covered by fine radiating striae, increased by interstitial additions, somewhat variable in size on the front slope, but quite uniform on the umbone and to the lateral margins; crossed by fine concentric striae. Interior not observed. “ Dorsal valve (exterior) gently concave to about the middle, where it makes a sudden curve, conforming to the shape of the other valve; the two valves are so closely drawn together as to leave scarcely any visceral space; beak very little elevated above the cardinal line; area no more than a rather sharp edge of the hinge; radiating striae, as far as observed same as on the ventral valve. Interior nearly flat, or slightly convex to the base of the ridge, in front and laterally to within about one-quarter or one-eighth of an inch of the cardinal line, where there is a flat depres- sion extending to the lateral margins; the curve to the front from the top of this ridge is abrupt, corresponding to the exterior; cardinal process bifid, erect, rather prominent, curving slightly anteriorly, crenulated 260 SYSTEMATIC PALEONTOLOGY posteriorly and sloping in the same direction; socket ridges short, crenu- lated, oblique; rounded, low, wavy elevations just beyond the points and in front of the socket ridges; a small but rather deep pit immediately in front of the cardinal process, from which extends a low mesial ridge to about the middle of the shell forwards, where it fades out; the concentric wrinkles of the exterior show through slightly, and the radiating striae plainly, with small, but distinct, radiating rows of papillae, which are rather distant from each other, to the ridge, but crowded together on the front slope and toward the lateral margins; no muscular scars observed, “ Width of a specimen of medium size, measuring from the points of the hinge-line, 14 inches ; length about three-fourths of an inch.”—James, 1874. Occurrence -—MARTINSBURG SHALB (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania. Eden shale of the Ohio Valley. Collections.—Maryland Geological Survey, U. S. National Museum. LEPTAENA TENUISTRIATA Sowerby var. Plate XLIX, Fig. 2 Leptaena tenuistriata Sowerby, 1839, in Murchison’s Sil. Syst., vol. ii, p. 636, pl. xxii, fig. 2a. Leptaena tenuistriata Foerste, 1910, Bull. Sci. Lab. Denison Univ., vol. xvi, p. 45, pl. v, fig. 9. Description The particular form of Leptaena found in the Sinuites bed of southern Pennsylvania is in general aspect quite like specimens from a similar lower Trenton horizon in Tennessee identified by Foerste as L. tenuistriata Sowerby. Direct comparison with typical British specimens is necessary before the identity of the American form can be determined with certainty. In the meantime it is believed best to record the Sinuites zone species as a variety. Occurrence.—MARTINSBURG SHALE (Sinuites bed). One mile south of St. Thomas and other localities in southern Pennsylvania. Collection.—U. 8S. National Museum. MaArYLAND GEOLOGICAL SURVEY 261 Genus RAFINESQUINA Hall and Clarke RAFINESQUINA CHAMPLAINENSIS Raymond Plate XLI, Figs. 8, 9 Rafinesquina champlainensis Raymona@, 1902, Bull. Amer. Pal., vol. iii, p. 37, pl. xviii, figs. 5, 6. Rafinesquina champlainensis Raymond, 1911, Ann. Carnegie Mus., vol. vii, D. 238, figs. 6-9. Description.—* Shell large, ventricose, almost hemispheric. Length and width nearly equal. Hinge line usually a little longer than the width below, and the cardinal extremities are produced into broad, rounded ears. The pedicle valve is strongly and evenly convex, the highest point being about the middle of the valve. The brachial valve is flat on the umbo and concave in front, following the curvature of the opposite valve. Cardinal area on the pedicle valve rather wide. Delthyrium covered by a broad convex deltidium. Area of brachial valve linear. The surface is marked by very numerous fine radiating striae, every third or fourth one of which is stronger than the ones between. The striae increase by implantation. In the partially exfoliated state in which the specimens are usually found, the striae appear nearly equal and the shell structure fibrous.”—-Raymond, 1902. Occurrence—CHAMBERSBURG LIMESTONE (Caryocystites bed). Fort Loudon and Blue Spring, Franklin County, Pennsylvania. In the type localities in the Lake Champlain area, this species occurs in the Middle Chazy (Crown Point) limestone. It has been identified in the stratigraphically equivalent Lenoir limestone of east Tennessee and Virginia. Collection.—U. S. National Museum. RaAFINESQUINA MINNESOTENSIS (Winchell) Plate XLV, Fig. 4 Strophomena deltoidea Owen (not Conrad), 1844, Geol. Expl. Iowa, Wis- consin and Illinois, pl. xvi, fig. 8; pl. xvii, fig. 6. Strophomena minnesotensis N. H. Winchell, 1881, Ninth Ann. Rept. Geol. Nat. Hist. Surv. Minnesota, p. 120. . 262 SYSTEMATIC PALEONTOLOGY Rafinesquina minnesotensis Hall and Clarke, 1892, Pal. New York, vol. viii, pt. 1, pl. 31, figs. 25-29. Rafinesquina minnesotensis Winchell and Schuchert, 1893, Geol. Minnesota, vol. iii, p. 401, pl. xxxi, figs. 25-29. Description.—* Shell semi-oblong or semi-oval, with the cardinal angle about 90, or less than 90; diameter from six to nine lines transversely, and from four and a half to eight lines perpendicularly ; the ventral valve convex, sometimes more suddenly deflected after passing the visceral area; dorsal valve gently concave, but reflexed more rapidly about the margin ; the exterior of the convex, ventral valve marked by fine, radiating striae, every third, fourth or fifth one being larger than the intervening ones; interior of the convex (ventral) valve, which is best known from its frequent casts, shows a large muscular impression somewhat bilobate in front and larger in proportion to the size of the valve; scars of adduc- tor muscles closely approximate, small and in many casts of this valve undistinguishable; behind they are separated (on the casts) by a short mesial ridge, which between them becomes a narrow mesial furrow and then a deep furrow, terminating at the sinus between the outer larger scars; the outer larger scars (diductors) are radiately striated from the beak (at the base of the dental lamellae small adjustors are occasionally indicated) ; their margins are strongly marked (on the cast) along their posterior sides by distinct grooves formed by the dental plates, which diverge at once from the foramen at an angle of 100-1200, running nearly straight to the outer margins of the muscular scar, when they curve slightly towards the front; the anterior and lateral margins of the general muscular impression are slightly marked on the casts; outside of the muscular scar is a shallow marginal impressed line which is most evident at the cardinal angles as it converges toward the beak; the interior edge of the cardinal line is carinate from the teeth to the cardinal angles; the details of the markings in the apex of the beak are seen on the valve itself to consist of two short, distinct, diverging ridges extending not much beyond the hinge teeth (enclosing the adductor scars), between the anterior ends of which rises a short mesial ridge of about the same size and length, with faint linear ridges parallel with it on each side, which a MarYLAND GEOLOGICAL SURVEY 263 extend a little further forward than the mesial ridge. The mesial ridge first gives place to a flat, unmarked interval, when it again rises more conspicuously, but narrower and sharper, extending nearly to the sinus separating the lobes of the outer muscular scar. The cardinal area of the convex valve slopes from the hinge-line obliquely backward, instead of being in plane with the lateral edges, thus differing from R. alternata. From three to five undulations of the shell transverse to the cardinal line are seen often between the umbo and the cardinal angles, the heavier ones being near the cardinal angles. The cardinal process is bifid and promi- nent, the two parts being short, smooth, dentate protruberances that stand prominently exposed about parallel with the plane of the cardinal area. “The interior of the dorsal valve is very different from that of the dorsal valve of Ff. alternata. The general visceral disc is nearly flat, sur- rounded by a suddenly flexed margin, inside of which is a shallow im- pressed broad line, most evident round the front; inside the cardinal angles are a few scattered, radiately interrupted, short ridges or elevations (genital markings), but these do not prevail along the side nor in front, the surface there being smooth or finely granulated instead ; in the center of the valve are five smooth, abrupt, digitately spreading ridges, the middle one of which is a little larger and longer than the others; these rise more abruptly at their anterior extremities than behind, but none of them reach the beak, or even the umbonal region, though the exterior pair of lateral ones are placed further back than the others, converging at an angle of about 700 (and often pass through the large pair of adductor scars). Socket (crural) ridges very short and widely divergent; behind them are small, doubly grooved sockets. The beak of the ventral valve is often perforated by a minute, circular, pedicle opening.”—Winchell and Schuchert, 1893. Occurrence. CHAMBERSBURG LIMESTONE (Hchinospherites bed). Wil- son and Pinesburg Station, Maryland. A characteristic Black River species of the Mississippi Valley. Collections.—Maryland Geological Survey, U. S. National Museum. 264 SYSTEMATIC PALEONTOLOGY RaPINESQUINA MINNESOTENSIS INQUASSA (Sardeson) Plate XLV, Figs. 5, 6 Strophomena inquassa Sardeson, 1892, Bull. Minnesota Acad. Nat. Sci., vol. iii, p. 334, pl. v, figs. 22-24. Rafinesquina minnesotensis var. inquassa Winchell and Schuchert, 1893, Geol. Minnesota, vol. iii, p. 403, pl. xxxi, figs. 27, 28. Description.—The brachiopod to which this varietal name has been applied differs from RB. minnesotensis in its larger and more convex shell with a wide ventral hinge area. Externally this shell also has a consider- able resemblance to R. alternata, but the interiors of each exhibit con- siderable difference, the two ridges on each side of the median septum in the present variety being reduced to one in R. alternata. Occurrence.—CHAMBERSBURG LimEsTONE (Echinospherites bed). Southern Pennsylvania and at Pinesburg Station and Wilson, Maryland. Collections.—Maryland Geological Survey, U. S. National Museum. RAFINESQUINA SQUAMULA (James) Plate LIV, Figs. 3-4; Plate LVIII, Fig. 4 Strophomena squamula James, 1874, Cincinnati Quart. Jour. Sci., vol. i, p. 335. Rafinesquina squamula Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, p. 264. Description Shell small, thin, semi-oval in outline, broader than long; hinge-line varying from a little more to a little less than the greatest breadth of the shell farther forward. “ Dorsal valve slightly convex or nearly flat; cardinal line straight; cardinal area linear; a slight depression immediately forward of the beak. Surface covered with fine, rounded radiating striae of nearly uniform size, increased toward the free margin by bifurcation. “Ventral valve slightly convex; beak and hinge-line slightly project- ing; cardinal area narrow, a little the widest in the middle; foramen triangular and nearly closed by the cardinal process of the other valve; a strong mesial rib extending from beak to the front; surface covered by fine, rounded, radiating striae, which bifureate once or twice before MaAryLanp GEOLOGICAL SURVEY 265 reaching the free margins ;.the striae starting at and near the beak more prominent than the branching ones; crossed by very fine concentric lines, visible only under a good magnifier, and even then in some cases quite obscure. Visceral space very little, the valves being so closely drawn together, translucent. Interior not observed. Breadth of a full-sized specimen, 5/8 inch; length, 1.2 inch.”—Foerste, 1914. Although hitherto unfigured the species has long been known as an interesting shell of the Cincinnati area where it occurs at several horizons in the Eden shale and in the Fairview formation of the Maysville group. The above description was based upon the type specimens and the ex- amples illustrated were identified by the author of the species. Occurrence.—AMARTINSBURG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania, and in sandstone fragments on Rickard Mountain, Washington County, Maryland. The Orthorhynchula bed at the top of the Fairview division of the Martinsburg shale, just under the Oswego sandstone, one and one-half miles southeast of McConnellsburg Pennsylvania, has furnished numerous specimens. Collections —Maryland Geological Survey, U. 8. National Museum. RAFINESQUINA ALTERNATA (Emmons) Plate LVII, Fig. 8 Strophomena alternata Emmons, 1842, Geol. New York, Rept. 2d Dist., p. 395, fig. 3. ; Leptaena alternata Hall, 1847, Pal. New York, vol. i, pp. 102, 286, pl. xxxi, fig. 1; pl. xxxiA, fig. 1; pl. xxix, fig. 2. Rafinesquina alternata Hall and Clarke, 1892, Pal. New York, vol. viii, pt. 1, p. 282, pl. viii, figs. 6-11, 27, 28; pt. 2, 1895, pl. Ixxxiv, figs. 17, 18. Description.—* Broadly semioval; length and breadth about as 12 to 15: hinge line, in perfect specimens, a little longer than the width of the shell, slightly reflected at the extremities, which sometimes become short, acute ears; cardinal area narrow, the callosity of the ventral valve nearly 266 SYSTPMATIC PALEONTOLOGY filling the triangular foramen of the dorsal valve; beak uniformly per- forated with a minute circular opening; dorsal valve depressed convex, sometimes more convex in the middle, suddenly deflected near the margin and flattened towards the cardinal line; ventral valve concave, gradually or sometimes suddenly inflected towards the basal margin ; surface marked by fine rounded radiating striae, which alternate at unequal intervals with coarser ones; striae increasing in number towards the margin of the shell, crossed by fine elevated concentric lines and a few imbricating lines of growth.”—Hall, 1847. This very abundant brachiopod has such a long range that it is of little value for detailed stratigraphic purposes, although it is true that the varieties or mutations of the species which occur at various horizons hold their characters fairly well if minute discriminations are made. The illustrations represent the common Maysville form of the species occur- ting in the Pulaski shale of New York. The same form occurs at the corresponding horizon in Pennsylvania and Maryland. Occurrence—MarTINSBURG SHALE (Fairview division). Tuscarora Mountain, one and one-half miles southwest of McConnellsburg, Penn- sylvania. Collections.—Maryland Geological Survey, U. 8. National Museum. Genus TRIPLECIA Hall TRIPLECIA (CLIFTONIA) SIMULATRIX N. sp. Plate XLIX, Figs. 11-13 Description.—The strata of the Chambersburg limestone succeeding the Lowville division and the Sinuites bed at the base of the Martinsburg shale, contain a radially plicated brachiopod which is so similar to small examples of Platystrophia that its references to that genus would seem proper. However, upon close examination this new species is found to have the characteristic bifurcated cardinal process of Triplecia and to lack the surface granulations of Platystrophia. The open delthyrium of Platystrophia is also absent, but the deltidium of the Strophomenidae is present. Manybtanp GEOLOGICAL SuRVEY 267 This species belongs to the genus or subgenus Cliftonia established by Foerste for the plicated forms of Triplecia, which was well described as Oxoplecia by Miss Alice Wilson. Triplecia (Cliftonia) simulatriz is related to Oxoplecia calhouni Wilson, from the base of the Collingwood (Trenton) shale of Ottawa, Canada, but differs in its coarser plication, this feature being most marked on the sides of the shell. Occurrence.—MartTINsBuRG SHALE (Sinuites bed). One mile south of St. Thomas, Pennsylvania, and at Strasburg, Virginia. The species occurs also in the Echinospherites, Nidulites, and Christiania beds of the Chambersburg limestone in Pennsylvania, Maryland, and Virginia. Collections—Maryland Geological Survey, U. 8. National Museum. Superfamily PENTAMERACEA Family SYNTROPHIIDAE Genus SYNTROPHIA Hall and Clarke SYNTROPHIA LATERALIS (Whitfield) Plate XXXIII, Figs. 4, 5 Triplesia lateralis Whitfield, 1886, Bull. Amer. Mus. Nat. Hist., p. 303, pl. xxiv, figs. 9-11. Syntrophia lateralis Hall and Clarke, 1892, Pal. New York, vol. viii, pt. 1, p. 270; ibid., vol. viii, pt. 2, p. 216, pl. Ixii, figs. 1-10. Syntrophia lateralis Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 126, pl. iv, figs. 14, 15. Syntrophia lateralis Walcott, 1912, Mon. U. S. Geol. Surv., vol. li, p. 802, text fig. 11, p. 299; pl. cii, figs. 6, 6a-g. Description.—Shell averaging 7.5 mm. in length and 11 mm. wide, subelliptical, with the hinge-line about two-thirds the greatest width and the cardinal extremities rounded. Pedicle valve somewhat convex, promi- nent on the umbo, but a little flattened near the cardinal angles; beak slightly incurved and rather blunt, projecting beyond the cardinal mar- gin; mesial sinus broad, shallow, and ill-defined, not extending to the beak. Surface with fine, concentric lines of growth. Occurrence._BEEKMANTOWN LIMESTONE (Cryptozoon steeli zone). At various localities around Williamsport and Hagerstown, Maryland. Collections.—Maryland Geological Survey, U. 8. National Museum. 268 SYSTEMATIC PALEONTOLOGY Family CLITAMBONITIDAE Genus SCENIDIUM Hall SCENIDIUM ANTHONENSE Sardeson Plate XLVII, Figs. 1-3 Scenidium anthonensis Sardeson, 1892, Bull. Minnesota Acad. Nat. Sci., vol. iii, p. 333, pl. iv, fig. 7. Scenidium halli Hall and Clarke, 1892, Pal. New York, vol. viii, pt. 1, p. 242, pl. viiA, figs. 33-39. Scenidium anthonensis Winchell and Schuchert, 1893, Geol. Minnesota, vol. iii, p. 381, pl. xxx, figs. 20-23. Scenidium anthonensis Weller, 1903, Geol. Surv. New Jersey, Pal., iii, p. 157, pl. x, figs. 5-7. Description.—* Shell small, subsemi-circular in outline, the greatest width along the hinge-line. Each valve marked by from 20 to 26 simple, rounded plications. Pedicle valve subpyramidal, the beak erect; cardinal area large, flat, broadly triangular, with a large delthyrium. Along the median line a slight elevation or ill-defined fold is developed. In the interior of the apical portion of the valve is a small spondylium. Brachial valve depressed, convex, with a slight mesial sinus. The dimensions of an average specimen are: Length, 2.5 mm., and breadth, 5 mm.”— Weller, 1903. Occurrence.—CHAMBERSBURG LimEsToNE (Nidulites bed). Wilson and Pinesburg Station, Maryland. Black River group of Minnesota, Iowa and New Jersey. Collections.—Maryland Geological Survey, U. S. National Museum. ScENIDIUM ? MEROPE (Billings) Plate L, Figs. 14-16 Orthis merope Billings, 1865, Geol. Surv. Canada, Pal. Fossils, vol. i, p. 139, fig. 116. Scenidium ? merope Hall and Clarke, ? 1892, Pal. New York, vol. viii, pt. 1, p. 242, pl. viiA, figs. 31, 32. Description.—Shell small, subpyramidal, somewhat semi-circular, with a width to the hinge-line of 6 mm. and a length of 3 mm. ; cardinal angles acute, from 60° to 70°; exterior surface marked with 25 to 30 strong MaryLAND GroLocicaL SURVEY 269 radiating striae. Ventral valve elevated, subpyramidal, most elevated at the beak, thence sloping nearly uniformly to the sides and margin; area large, triangular, at right angles to the plane of the margin; foramen large, extending to the beak. Dorsal valve nearly flat, with an obscure mesial sinus. This interesting little brachiopod is somewhat similar to several small striated forms, and a restudy of the types is necessary before its true generic characters can be determined. The shell from Cincinnati, Ohio, figured by Hall and Clarke in 1892, is very probably of a distinct species. Occurrence —ManrvinsBurG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Trenton limestone at Ottawa, Canada. Collection.—U. S. National Museum. Family PORAMBONITIDAE Genus PARASTROPHIA Hall and Clarke PARASTROPHIA HEMIPLICATA Hall Plate XNLVIII, Figs. 8-11 Atrypa hemiplicata Hall, 1847, Pal. New York, vol. i, p. 144, pl. xxxiii, fig. x. Anastrophia ? hemiplicata Winchell and Schuchert, 1893, Geol. Minnesota, vol. iii, p. 382, pl. xxx, fig. 29-31. Parastrophia hemiplicata Hall and Clarke, 1893, Pal. New York, vol. viii, pt. 2, p. 221, pl. Ixiii, figs. 1-3. Parastrophia hemiplicata Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 158, pl. x, figs. 11-14. Parastrophia hemiplicata Wilson, 1914, Canada Geol. Surv. Mus. Bull. No. 2, pp. 1-10, pl. iv, figs. 1-34. Description. Shell subglobose, subpentagonal in outline, wider than long, the thickness frequently equal to the length. Cardinal line short, with sometimes the appearance of a small area on the pedicle valve. Each valve marked by from 8 to 12 simple, subangular, radiating plications, which reach from one-third to one-half the distance from the margin to the beak, leaving the older portion of each valve smooth. Besides the radiating plications, the entire surface is marked by fine, concentric, sub- imbricating lines of growth, which are more conspicuous near the margin 270 SYSTEMATIC PALEONTOLOGY of the shell. Pedicle valve depressed-convex, with an abrupt, broad, but not deep sinus, which originates about one-third of the distance from the beak to the anterior margin and is produced as a lingual extension in front at nearly a right angle to the plane of the valve; it is marked by from three to five radiating plications. The beak is small, closely in- curved; delthyrium small and triangular. Brachial valve strongly con- vex or gibbous, with a broad mesial fold commencing one-third of the distance from the beak to the anterior margin, which is marked by from four to six radiating plications. “ The dimensions of a perfect individual are: Length, 13 mm.; width, 16.5 mm.; thickness, 12.5 mm.”—Weller, 1903. Occurrence.—CHAMBERSBURG LIMESTONE (Christiania bed). South- ern Pennsylvania. Trenton limestone of New York, New Jersey, etc. Collections.—Maryland Geological Survey, U. 8S. National Museum. Order TELOTREMATA Superfamily RHYNCHONELLACEA Family RHYNCHONELLIDAE Genus CAMAROTOECHIA Hall and Clarke CAMAROTOECHIA PLENA (Hall) Plate XLI, Figs. 14-16 Atrypa plena Hall, 1847, Pal. New York, vol. i, p. 21, pl. iv, figs. 7. Camarotoechia plena Raymond, 1911, Ann. Carnegie Mus., vol. vii, p. 221, pl. xxxiii, figs. 7-18. Description“ The adult shells are subtriangular to subcircular in outline, with a wide, shallow ventral sinus and a somewhat elevated dorsal fold. Surface marked by from 17 to 24 strong plications, four to seven of which are in the sinus and five to eight on the fold. The plications are crossed by zigzag lines of growth, which are sometimes stronger and sometimes weaker on partially exfoliated specimens than of specimens with perfect shells. The dorsal beak is strongly incurved, and the umbo bears a slight median depression. The beak of the pedicle valve is only MARYLAND GEOLOGICAL SURVEY 271 slightly incurved, and does not rest against the brachial valve. The delthyrium is open throughout life. None of the specimens in the collec- tion show the deltidial plates. “ Casts of the interior of the brachial valve show a low septum which extends about one-third the length of the shell. This septum divides at its posterior end as in the typical species of Camarotoechia, but there is no cardinal process as in Rhynchotrema.”—Raymond, 1911. One of the most abundant and characteristic Upper Chazyan (Val- cour) fossils of the Lake Champlain region in New York and in Canada. - Occurrence CHAMBERSBURG LIMESTONE (Caryocystites bed). In the strip of outcrop from Fort Loudon to Blue Spring, Franklin County, Pennsylvania. Collections.—Maryland Geological Survey, U. S. National Museum. Genus ORTHORHYNGCHULA Hall and Clarke ORTHORHYNCHULA LINNEYI (James) Plate LVII, Figs. 9-12 Orthis ? linneyi James, 1881, Paleontologist, vol. v, p. 41. Orthorhynchula linneyi Hall and Clarke, 1893, Pal. New York, vol. viii, pt. 2, p. 181, pl. lvi, figs. 10-13, 19. Description.—* Shells rhynchonelloid in contour; hinge-line short, straight, extending for about one-third the transverse diameter of the valves. A true cardinal area is present on both valves, that of the pedicle- valve being considerably the broader, erect, often incurved. Each valve also possesses a distinct triangular delthyrium, that of the pedicle-valve, according to the evidence at hand, never being in any degree closed by deltidial plates. External surface strongly and simply plicated, the median fold and sinus being well developed. On the interior, the pedicle- valve possesses blunt teeth which rest upon the laterally thickened walls of the valve and are not supported by lamellae. Between, and slightly in front of these lies a short, subquadrate muscular scar. The brachial valve possesses a linear cardinal process, on either side of which are two discrete crural plates, sharply concave on the upper surface and diverging 18 272 SYSTEMATIC PALEONTOLOGY anteriorly for a considerable distance. Shell-substance fibrous, im- punctate.”—Hall and Clarke, 1893. Although occurring at two distinct geological horizons this interesting brachiopod, when considered with the associated fossils, is highly char- acteristic of each horizon. The species is so well developed at the top of the Fairview formation of the Maysville group that the name Ortho- thynchula bed has been applied to these strata. ‘In this bed the species often grow to an unusual size, some examples being an inch or more in length. Occurrence—MarTINSBURG SHALE (Fairview division). Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Pennsyl- vania. Upper Trenton of Kentucky and Tennessee, Lower Maysville of the Ohio Valley, Virginia, Maryland, and Pennsylvania. Collections.—Maryland Geological Survey, U. S. National Museum. Genus ZYGOSPIRA Hall ZYGOSPIRA REOCURVIROSTRIS (Hall) Plate XLII, Figs. 9-12 Atrypa recurvirostris Hall, 1847, Pal. New York, vol. i, p. 140, pl. xxxiii, fig. 5. Zygospira recurvirostris Winchell and Schuchert, 1893, Geol. Minnesota, vol. iii, p. 466, pl. xxxiv, figs. 38-41. Zygospira recurvirostris Hall and Clarke, 1895, Pal. New York, vol. viii, pt. 2, pl. liv, figs. 1-6. Zygospira recurvirostris Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 161, pl. x, figs. 23-26. Description.—* Shell small, subcircular or longitudinally subovate in outline, subglobular ; surface of both valves marked by 24 to 28 rounded or subangular, radiating plications, which are crossed by fine, concentric ‘ lines of growth. Pedicle valve gibbous, with its greatest elevation near the center, subcarinate near the beak, the keel becoming broader toward the front and forming a rather well-defined, more or less flat-topped median fold; beak small and pointed, incurved over the beak of the brachial valve. Brachial valve less convex than the other, marked by a MARYLAND GEOLOGICAL SURVEY 273 rather broad, shallow, rounded median sinus, which corresponds with the fold of the pedicle valve and which reaches nearly to the beak. The dimensions of an average specimen are: Length, 6 mm.; width, 6 mm.; thickness, 4 mm.”—Weller, 1903. An abundant species in its various forms, in the Black River and Trenton rocks of New York and Canada and the Ohio and Mississippi valleys. : Occurrence —CHAMBERSBURG LIMESTONE (Tetradium cellulosum bed). Railroad cut two miles southwest of Marion and at Fort Loudon, Franklin County, Pennsylvania, where the Lowville form occurs in some abundance. Collections —Maryland Geological Survey, U. 8. National Museum. ZYGOSPIRA EXIGUA (Hall) Plate XLVITI, Figs. 19, 20 Atrypa exigua Hall, 1847, Pal. New York, vol. i, p. 141, pl. xxxiii, fig. 6. Protozyga exigua Hall and Clarke, 1893, Pal. New York, vol. viii, pt. 2, p. 149, figs. 187, 138, pl. liv, figs. 47, 48. Description Plano-convex ; length and breadth about equal; cardi- nal line considerably extended; dorsal valve elevated in a ridge along the middle, depressed at the sides, and slightly inflected towards the cardinal extremities; beak small, straight, much extended beyond the cardinal line ; ventral valve considerably shorter than the dorsal, depressed-convex, with a broad depression along the center, reaching half way from the base to the beak; beak small, and close pressed into the foramen beneath the beak of the opposite valve; surface scarcely marked with fine concentric lines, and a few indistinct longitudinal rays near the margin. “Tn the largest specimen which IJ have seen, there are evidences, under a magnifier, of small radii commencing below the center of the valve. Since, however, they are not perceptible to the naked eye, they are. of minor importance, unless it should be found that this is the young of a species which changes with growth. The specimens yet seen, however, are minute, and it may properly be doubted whether the species attains avd SYSTEMATIC PALEONTOLOGY a size beyond the largest figures given. The valves are often close pressed, and deflected at the margin.”—Hall, 1847. Occurrence—CHAMBERSBURG LIMESTONE .(Christiania bed). Green- castle and other localities in southern Pennsylvania. Trenton limestone of New York. Collection.—U. 8S. National Museum. ZYGOSPIRA MoDESTA (Hall) Plate LIV, Figs. 20-22; Plate LVII, Figs. 13-16 Atrypa modesta (Say) Hall, 1847, Pal. New York, vol. i, p. 141, pl. xv, fig. 15. Zygospira modesta Meek, 1873, Pal. Ohio, vol. i, p. 125, pl. ii, fig. 4. Zygospira modesta Winchell and Schuchert, 1893, Geol. Minnesota, vol. iii, p. 465, pl. xxxiv, figs. 42-44. Zygospira modesta Hall and Clarke, 1893, Pal. New York, vol. viii, pt. 2, p. 155, figs. 146-149; pl. liv, figs. 7-10, 12. Description.—< Shell small, rather depressed, nearly plano-convex, sub- orbicular, or straightened and converging to the beaks at an obtuse angle; lateral margins more or less rounded; front rounded, or sometimes a little straightened, or very slightly sinuous at the middle. “ Dorsal valve with a rather shallow, undefined mesial sinus of moderate breadth at the front, but becoming rapidly narrower, and less impressed posteriorly, so as often to die out before reaching the umbo; surface on each side of the sinus gently convex centrally, and sloping gradually to the lateral margins ; beak but slightly prominent and incurved. “ Ventral valve, with a low mesial ridge, corresponding to the sinus of the other valve, excepting that it is generally most prominent near the middle, and somewhat depressed anteriorly; while on each side of the ridge the slopes are distinctly compressed ; beak small, abruptly pointed, projecting beyond that of the other valve, and rather distinctly arched; but not so closely incurved as to conceal the small fissure, which seems to be closed below by a deltidium, that leaves a minute aperture above, just under, or extending to, the apex; margin on each side of beak cari- nated, so as to give the appearance of a kind of false cardinal area. MARYLAND GEOLOGICAL SURVEY 275 “Surface of each valve ornamented by about 16 to 18 small, simple, radiating plications, of which about three to five near the front of the dorsal valve occupy the mesial sinus, the middle one being usually a little the largest; while on the ventral valve about four of the largest occupy the mesial prominence, the furrow between the middle two being generally a little larger and deeper than the others; marks of growth undefined, or extremely minute and obscure. Length of a mature, moderately large specimen, 0.26 inch; breadth, 0.30 inch; convexity, 0.15 inch.”—Meek, 1873. An abundant Cincinnatian fossil at many localities in the United States and Canada. In Maryland and Pennsylvania the species occurs in the upper part (Eden) of the Martinsburg shale and in the succeeding Fairview formation. Occurrence.—MarTINsBURG SHALE (Eden Division). Rickard Moun- tain and Fairview Mountain, Washington County, Maryland. Collections.—Maryland Geological Survey, U. S. National Museum. ZYGOSPIRA ? ERRATICA (Hall) Plate LVII, Figs. 17-23 Orthis ? erratica Hall, 1847, Pal. New York, vol. i, p. 288, pl. Ixxix, fig. 5. Catazyga erratica Hall and Clarke, 1893, Pal. New York, vol. viii, pt. 2, p. 158, pl. liv, figs. 17-23. Description —* Subhemispherical, orbicular ; dorsal valve very convex, with the mesial portion abruptly elevated, flat above ; ventral valve convex at the sides, depressed in the middle, and considerably elevated in front; surface marked by fine simple uniform striae.”—Hall, 1847. This species is readily distinguished: from Zygospira modesta with which it is associated, by its larger size, greater convexity, and especially by the numerous fine striae. A characteristic fossil of the Pulaski shales of New York and Canada. Occurrence—MartiInsBurG SHALE (Fairview division). Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Penn- sylvania. Collections.—Maryland Geological Survey, U. 8S. National Museum. 276 SYSTEMATIC PALEONTOLOGY VERMES Order TUBICOLA Genus CORNULITES Schlotheim CoRNULITES FLExUosUS (Hall) Plate LVI, Fig. 18 Tentaculites ? flecuosa Hall, 1847, Pal. New York, vol. i, p. 92, pl. xxix, figs. 6a-d, p. 284, pl. Ixxviii, figs. 2a, b. , Cornulites flexuosus Hall, 1888, Pal. New York, vol. vii, Supp. 1; p. 18, pl. exv, figs. 41, 42. Description“ Tubes single or aggregate, adhering, more or less curved at the tip or along the whole length; surface marked by strong annulations somewhat irregular; interior distinctly septate; septa with the concave sides upwards.”—Hall, 1847. Occurrence —MarTINSBURG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania, and Tus- carora Mountain, two and one-half miles southeast of McConuellsburg, Pennsylvania. Collections.—Maryland Geological Survey, U. 8. National Museum. WORM BURROWS (?) Genus SCOLITHUS Haldemann ScoLITHus LINEARIS (Haldemann) ~ Plate XXV, Fig. 9 Fucoides ? linearis Haldemann, 1840, Supp. Monograph Limniades, p. 3. Scolithus linearis Hall, 1847, Pal. New York, vol. i, p. 2, pl. i, figs. 1a-1c. Scolithus linearis Walcott, 1890, 10th Ann. Rep. U. S. Geol. Surv., p. 603, pl. lxiii, figs. 1, la-c. Description.—The pencil-like fillings of the worm burrows to which the above name is applied have a wide distribution in the arenaceous Cambrian rocks of Eastern North America. The species is determined in large part by its geological position and by the diameter of the tubes. Scolithus linearis forms free cylindrical or subcylindrical, unbranched, MarYLAND GEOLOGICAL SURVEY Q07 vermiform tubes with their surface usually smooth, but sometimes appar- ently striated. Their form is rigidly straight and they range in length from several inches to a foot or more. The diameter varies between one- eighth to one-half an inch. These tubes preserve their distinctness under almost all conditions and they often stand out quite clearly in the rock. Occurrence—Harprrs SHALE AND ANTIETAM SANDSTONE. In Mary- land this species has been identified at Eakles Mills and other localities, particularly in the drift blocks along the west front of the Blue Ridge. Widely distributed in the Cambrian of Perinsylvania, New York, Vir- ginia, Canada, etc. Collections —Maryland Geological Survey, U. S. National Museum. MOLLUSCA crass PELECYPODA Order PRIONODESMACEA Family CTENODONTIDAE “Genus CTENODONTA Salter CTENODONTA GIBBERULA Salter Plate XLIT, Figs. 18-20 Ctenodonta gibberula Salter, 1857, Canadian Org. Rem. Dec. I, p. 38, pl. viii, fig. 6. Tellinomya ventricosa Meek and Worthen, 1868, Geol. Surv. Illinois, vol. iii, p. 307, pl. ii, figs. 7a-c. Ctenodonta gibberula Ulrich, 1894, Geol. Minnesota, Pal., vol. iii, pt. 2, p. 587, pl. xlii, fig. 37, text figs. 44f-g, p. 599. Description.— Shell rhombic subovate, ventricose, the height, length and thickness, respectively, as seven, ten, and six, with large incurved beaks, situated a little behind the mid-length; antero-dorsal and ventral margins subparallel, the posterior end obliquely truncate above the narrow and sharply rounded lower part; anterior end broadly rounded and con- tinuing into the basal margin; the latter is straight or very gently sinuate and ascends from the prominently rounded anterior part; posterior 278 SYSTEMATIC PALEONTOLOGY umbonal ridge inconspicuous in a lateral view, rather sharply defined, however, in a dorsal view by a narrow furrow which outlines a wide lanceolate flattened area, equally divided by the hinge lme, and in the upper part of which (immediately behind the beaks) the ligament is attached to distinct fulcra; anterior dorsal slope abruptly rounded; entire anterior half of valves strongly ventricose, while between this part and the posterior umbonal ridge a slight sulcus crosses from near the beak to the base. Surface marked by rather distinct, closely arranged, subequal concentric striae of growth, tending to irregularity in the basal parts of old shells. “Impressions of adductor muscles extremely deep, the anterior pair larger than the posterior. A small, though distinct, pedal muscle scar is always present on the upper part of the strong ridge which forms the inner boundary of the anterior adductor (in casts it lies at the bottom of the deep cavity produced by this ridge), but the corresponding posterior scar is rarely distinguishable. Hinge plate very narrow at the beaks, but widening rapidly on each side, the anterior half somewhat the stronger and slightly concave along its inner margin, both terminating abruptly at the muscular scars; denticles 12 behind and 10 or 11 in front, those near the beaks very small, all interlocking deeply, especially those of the anterior set, which are also scmewhat larger than the posterior. The shell is very thick and the rostral filling so considerable that in casts of the interior the beaks appear obtuse and widely separated.”—Ulrich, 1894. A characteristic Black River species of Canada, New York, and the Ohio and Mississippi valleys.. Occurrence.—CHAMBERSBURG LimEsToNE (Tetradium cellulosum bed). Fort Loudon, Franklin County, Pennsylvania. Collections.—Maryland Geological Survey, U. 8. National Museum. CTENODONTA OBLIQUA Hall Plate LIV, Figs. 17-19 Nucula obliqua Hall, 1845, Amer. Jour. Sci., vol. xliii, p. 292. Tellinomya ? obliqua Meek, 1873, Pal. Ohio, vol. i, p. 139, pl. xi, figs. 11a-c. Ctenodonta obliqua Ulrich, 1894, Geol. Minnesota, vol. iii, pt. 2; p. 604, pl. xlii, figs. 83-87. MarYLAND GEOLOGICAL SURVEY 279 Description.—* Shell very small, compressed, subcircular, approaching subquadrangular ; height and breadth about equal; anterior margin short and rounding or less rounded ; beaks elevated, nearer the anterior margin ; dorsal margin sloping from the beaks, the anterior slope being the more abrupt, and the margin behind the beaks straighter, more compressed and sharper ; surface smooth ; internal casts showing the muscular impressions to be comparatively rather distinct. Hinge unknown. Length, 0.06 inch; height slightly less ; convexity, 0.03 inch.”—Meek, 1873. As indicated above, the hinge of this small pelecypod is unknown, as no specimens have ever been found preserving the shell structure. Like Cyclora minuta and other dwarfed gastropods and pelecypods, the species occurs only as phosphatized casts or as molds in the rock. Such casts of C. obliqua, however, occasionally show a denticulated margin along the hinge line such as would be left by the denticles of a species of Ctenodonta. This abundant small pelecypod was described from specimens found at Cincinnati, Ohio, but it ranges in age from the Trenton to and through the Richmond and occurs in many states. Occurrence.—M srTINsBURG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania. Collections—Maryland Geological Survey, U. 8. National Museum. CTENODONTA FILISTRIATA Ulrich Plate LIV, Figs. 26-29 Ctenodonta filistriata Ulrich, 1894, Geol. Minnesota, vol. iii, pt. 2, p. 599, figs. 44a-e. Description.—This species has usually been identified with the Trenton species Ctenodonta levata Hall, but it may be distinguished from this and similar forms by the delicate, crowded, thread-like concentric lines which cover the entire surface. Twelve to twenty of these lines may be counted in a space 1 mm. wide. This surface ornamentation in connection with the subovate forms of the shell and the rows of denticles on the hinge, causes the species to be easily recognized. 280 SYSTEMATIC PALEONTOLOGY Occurrence—ManrTINsBuRG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania. Eden shale at Cincinnati, Ohio. Collection.—U. S. National Museum. Family LEDIDAE Genus CLIDOPHORUS Hall CLIDOPHORUS PLANULATUS (Conrad) Plate LIV, Fig. 37 Nuculites planulata Conrad, 1841, 5th Ann. Rept. New York Geol. Surv., p. 50. Cleidophorus planulatus Hall, 1847, Pal. New York, vol. i, p. 300, pl. Ixxxii, figs. 9a-e. Description.—* Shell transversely elliptical oblong, height about half the length of the shell, with the beak approximately a third of the length of the shell from the anterior end. Umbonal ridge low, distinctly defined along its cardinal border where it makes an angle of 162 to 165 degrees with the longitudinal axis of the shell. Above this umbonal ridge, the posterior cardinal slope of the shell is flattened and subalate. The pos- terior part of the hinge-line extends from the beak for a distance equalling about two-fifths the length of the shell, and then makes an angle of about 150 degrees with the posterior margin of the shell. The margin is rather strongly rounded at both the posterior and anterior ends of the shell, the maximum curvature of the anterior margin, however, being nearer the hinge-line. The basal margin is moderately and evenly convex. The clavicular adductor support anterior to the beak forms an angle of about 80 degrees with the longitudinal axis of the shell; it is comparatively straight and extends downward to about the middle height of the shell; it is sharp and narrow, appearing on the cast of the interior of the shell as a sharp incision not depressing the immediately adjoining part of the shell. The convexity of the shell is moderate, that of a shell 9 mm. in height being about 1.6mm. Specimens 20 mm. in length occur.”—Foerste, 1914. MaryLANpD GEOLOGICAL SURVEY 281 Occurrence.—MARTINSBURG SHALE (Eden division). Rickard Moun- — tain, Washington County, Maryland. Eden shale and Maysville group of New York and Ohio. Collection—U. 8. National Museum. Family CYRTODONTIDAE Genus ISCHYRODONTA Ulrich IsCHYRODONTA UNIONOIDES (Meek) Plate LVITI, Figs. 2, 3 Anodontopsis ? unionoides Meek, 1871, Amer. Jour. Sci., vol. ii, p. 299. Anodontopsis (Modiolopsis ?) unionoides Meek, 1873, Pal. Ohio, vol. i, p. 141, pl. xii, figs. 2a, b. Ischyrodonta unionoides Ulrich, 1893, Geol. Surv. Ohio, vol. vii, p. 677, pl. liv, figs. 1-3. Ischyrodonta curta Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, p. 298, pl. iii, fig. 14. Description.—“ Shell of medium size, subovate, a little the highest posteriorly, compressed, convex, thickest slightly above and in advance of the middle. Anterior margin regularly but rather narrowly rounded; base forming a broad semielliptic curve; posterior margin broadly . rounded, very slightly oblique; dorsal outline more or less strongly arcuate, passing gradually into the ends. Beaks small, compressed, pro- jecting very little beyond the hinge margin, placed between one-fourth and one-fifth of the length of the valves behind the anterior extremity ; umbonal ridge scarcely distinguishable. Surface showing only a few dis- tinct subimbricating marks of growth. “ Hinge comparatively weak for the genus, with one oblique cardinal tooth in the right valve and two (?) in the left. The ridge-like internal ligament support leaves a linear depression within the dorsal edge extend- ing posteriorly from the beak for a distance equaling about one-third of the length of the shell. Anterior adductor and pedal muscle attachments having the characters usual for the genus, except that they are, with respect to the beaks, more anterior in position for the reason that the anterior end is uncommonly long.”—Ulrich, 1893. 282 SYSTEMATIC PALEONTOLOGY Occurrence—MAaARTINSBURG SHALE. (Top of the Fairview Orthor- hynchula bed) just under the Oswego sandstone on Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Pennsylvania. Top of the Fairview or base of the McMillan formation at Cincinnati, Ohio. Pulaski shales of New York and Canada. Collections.—Maryland Geological Survey, U. S. National Museum. Family AMBONYCHIIDAE Genus BYSSONYGHIA Ulrich ByssonrcHia VERA (Ulrich) Plate LIV, Figs. 34-36 Byssonychia vera Ulrich, 1893, Geol. Surv. Ohio, vol. vii, p. 629, figs. a-c. Ambonychia cincinnatiensis Miller and Faber, 1894, Jour. Cincinnati Soc. Nat. Hist., vol. xvii, p. 24, pl. i, figs. 8-10. Description.—This species is quite similar to Byssonychia radiaty (Hall), the type of the genus, and in fact is frequently identified with it, but B. vera differs in its smaller size, finer striae (there being about 50 to from 37 to 40 in the typical form of that species), shorter hinge line, more evenly convex valves, and shorter byssal opening. Occurrence.—MarTINSBURG SHALE (Eden division). Southern Penn- sylvania, and in the sandstone debris of Rickard Mountain, Maryland. Eden shale of the Ohio Valley. Collections—Maryland Geological Survey, U. 8. National Museum. ByYssonYCHIA RADIATA (Hall) Plate LVII, Fig. 26 Ambonychia, radiata Hall, 1847, Pal. New York, vol. i, p. 292, pl. xxx, figs. 4a-l. Ambonychia radiata Hall and Whitfield, 1875, Geol. Surv. Ohio, Pal., vol. ii, p. 79, pl. ii, fig. 2. Byssonychia radiata Ulrich, 1897, Geol. Minnesota, vol. iii, pt. 2, p. 477, fig. 35VI. Byssonychia radiata Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, p. 278, pl. iii, figs. 12a-c. Description.—“ Shell small to medium sized, varying in outline from subquadrangular, with a rounded base, to acutely ovate, according to the MaryLAND GEOLOGICAL SURVEY 283 degree of obliquity of the body of the shell to the direction of the hinge- line. Surface of the shell ventricose, and often subcarinate on the umbones and towards the beaks, gradually and somewhat regularly sloping to the basal margin, becoming attenuate and compressed toward the postero-cardinal region, and abruptly truncate and even impressed on the anterior side. Beaks acutely pointed, strongly incurved, terminal and projecting above the line of the hinge; posterior end at right angles to the hinge straight or rounded, or sometimes sloping obliquely backwards to the postero-basal margin; base sharply rounded. Anterior border of the valves excavated below the beaks, forming a rather large byssal opening, which is usually about half as wide as long when the valves are united. “Surface of the valves marked by strong, radiating ribs, which are simple throughout, strongest on the body of the shell, and becoming finer on the postero-cardinal region. On the upper portion of the shell the ribs are flattened on the top, and often grooved in the center, giving them a strongly duplicate character, but becoming smooth below, the spaces between as narrow, or much narrower, than the width of the rib. The ribs are crossed by fine, concentric, imbricating lines of growth, which undu- late as they cross the elevation.”—Hall and Whitfield, 1875. Occurrence.—MAnTInsBuRG SHALE (Fairview division). Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Pennsyl- vania. Marysville group of the Ohio Valley and Canada. Collections —Maryland Geological Survey, U. 8. National Museum. ByYSsSONYCHIA PRAECURSA Ulrich Plate LVII, Figs. 28, 29 Byssonychia praecursa Ulrich, 1893, Geol. Surv. Ohio, vol. vii, p. 633, pl. xlv, figs. 1, 2. Description.—In outline and number of costae this species is quite similar to Byssonychia radiata with which it is associated, but it is less oblique, the hinge is longer, and the central part of the valve is somewhat narrower. The marked difference between the two, however, lies in the flattening of the anterior side in B. praecursa. 284 SYSTEMATIC PALEONTOLOGY Occurrence.—MArtTINsBuRG SHALE (Fairview division). Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Pennsyl- vania. A characteristic fossil of the Pulaski shale of New York and of the corresponding horizon (Fairview division of the Maysville group) in the Ohio Valley. Collection.—U. S. National Museum. Genus ALLONYCHIA Ulrich ALLONYCHIA OvaTA Ulrich Plate LVII, Fig. 27 Allonychia ovata Ulrich, 1893, Geol. Surv. Ohio, vol. vii, p. 642, pl. xlviii, figs. 4-6. Description.—Shell large, 55 mm. in length and 36 mm. wide, subovate but almost erect, strongly convex. Hinge line short not alated posteriorly with the beaks large, incurved and not terminal. Surface marked with 40 to 45 radially arranged costae. Hinge line short, edentulous, with a high ligamental area. A fairly well preserved cast in sandstone from Tuscarora Mountain, Pennsylvania, exhibited all the characters of this well-marked species. Occurrence-—Martinspure SHALE (Fairview division). ‘Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Penn- sylvania. Upper part of Fairview formation at Covington, Kentucky. Collection.—U. 8. National Museum. Family AVICULIDAE Genus PTERINEA Goldfuss PTERINEA (CARITODENS) DEMISSA (Conrad) Plate LVII, Fig. 24 Avicula demissa Conrad, 1842, Jour. Acad. Nat. Sci. Philadelphia, vol. viii, p. 242, pl. xiii, figs. 3. Avicula demissa Hall, 1847, Pal. New York, vol. i, p. 292, pl. lxxxix, fig.-2a, b. Pterinea demissa Hall and Whitfield, 1875, Geol. Surv. Ohio, Pal., vol. ii, p. 78, pl. ii, fig. 1. Caritodens demissa Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, p. 269, pl. i, figs. 10, pl. 3, fig. 11. MarYLAND GEOLOGICAL SURVEY 285 Description.—* Shell subrhomboidal in outline, with the basal margin rounded; hinge-line much longer than the body of the shell; anterior wing extended into a rather long, acute point, when perfect, forming nearly one-third of the length of the hinge, measured from the point of the beak ; posterior wing large, rather obtusely pointed, and extending as far as the body of the shell below ; body of the shell oblique, a line drawn from the beak to the center of the base forming an angle with the posterior hinge-line of about 65 or 70 degrees; posterior margin of the shell broadly and roundly, but not deeply, excavated between the posterior wing and the postero-basal extremity of the shell; basal margin rather sharply rounded ; anterior margin obliquely sloping from the hinge-line, being nearly parallel with the body of the shell; very slightly excavated below the anterior alation. Left valve strongly convex when not com- pressed, prominent and rounded in the center, but flattened and slightly concave toward the alations; beak small, extending but little above the hinge-line; flattened or depressed convex on the umbo. Right valve concave, the concavity not exceeding one-half of the convexity of the opposite valve, and usually somewhat shorter on the basal portion. “ Surface of the convex valve marked by regular, concentric, lamellose lines, the edges of which are sharply elevated when well preserved, giving an exceedingly roughened character to the surface. In the degree of this latter feature, as also in the relative distance of the lines, there is con- siderable variation in different individuals. Surface of the concave valve distinctly lamellose, but the precise features have not been very clearly determined, as no very good specimens of this valve have been examined.” —Hall and Whitfield, 1875. ‘A detailed description of this species, particularly of the shell structure, was given by Foerste in 1914, but the above-quoted description applies better to the specimens as found in the Cumberland Valley of Maryland and Pennsylvania. Occurrence—MArTINsBuRG SHALE (Fairview division). ‘Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Pennsyl- vania. Not uncommon in the Maysville and Richmond groups of the Ohio Valley, New York, and Canada. Collections.—Maryland Geological Survey, U. 8. National Museum. 286 SYSTEMATIC PaLEonToOLOGY Family LYRODESMIDAE Genus LYRODESMA Conrad LiyRopESMA CONRADI Ulrich Plate LIV, Fig. 30 Lyrodesma conradi Ulrich, 1893, Geol. Surv. Ohio, vol. vii, p. 684, pl. xlvii, fig. 9. Description.— Shell a little oblique, transversely subovate, somewhat the highest across the middle of the posterior end; length 15 to 22 mm., height 11.5 to 15 mm., thickness about half the height; just beneath the middle of the slightly oblique posterior margin, the outline is a little produced and more narrowly rounded than elsewhere. Valves moderately convex, the posterior umbonal ridge rounded, not a prominent feature, the beaks small, situated just within the anterior third of the length. Surface marked by very fine, closely arranged, sharp concentric lines, crossed on the posterior cardinal slope by about ten radiating striae. Hinge with seven teeth of the usual type in each valve. Adductor scars distinct, the posterior one rather small and situated a very short distance beneath the submarginal pedal muscle impression. Pallial line with a small though undeniable posterior sinus. A peculiar feature of internal casts is the broad and shallow furrow shown in the figure just in front of the umbonal ridge.”—Ulrich, 1893. Occurrence.—MARTINSBURG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania. Eden shale at Cincinnati, Ohio. Collection —U. S. National Museum. Family MODIOLOPSIDAE Genus MODIOLOPSIS Hall MopIoLOPsIS MODIOLARIS (Conrad) Plate LVIII, Fig. 12 Pterinea modiolaris Conrad, 1838, 2d Ann. Rept. Geol. Surv. New York, p. 118. Modiolopsis modiolaris Hall, 1847,-Pal. New York, vol. i, p. 294, pl. 81, figs. la-g; pl. lxxxii, fig. 1. Modiolopsis modiolaris Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, p. 281, pl. iii, fig. 1; pl. v, figs. 1, 2. MaryLaNnpD GEOLOGICAL SURVEY 287 Description.-—“ Shell obliquely oblong. The cardinal margin posterior to the beak nearly straight, rounding gradually into the oblique posterior margin. Anterior to the beak, the cardinal margin is deflected down- ward, and then rounds into the strongly curved anterior margin of the shell. Basal margin straight along that part of the shell which lies directly opposite the straight cardinal margin; rising gradually toward the curved anterior margin, and more rapidly towards the posterior margin, which is most curved at the posterior extremity of the umbonal ridge. Umbonal ridge most strongly defined on the cardinal side and within about 10 or 15 mm. from the beak, almost disappearing into the general convexity of the shell posteriorly. Mesial sinus practically obsolete, although occasional specimens show a very faint indication of the same accompanied by a scarcely perceptible concavity of the basal outline. General convexity of the shell small. Concentric striations best defined anteriorly, along that part of the shell which is anterior to the oblique umbonal ridge. Anterior adductor depressions large and dis- tinctly defined, although usually very shallow, owing to the thinness of the shell. The interior of one of the valves is faintly striated posteriorly, below the umbonal ridge, in a direction parallel to a line drawn from the posterior termination of the umbonal ridge to a point half way between the beak and the upper anterior margin of the shell.”—Foerste, 1914. Numerous references have been made to this species in the literature and it has undoubtedly been misidentified many times. The only serious study of this pelecypod is that in 1914 by Foerste whose description is quoted above. Modiolopsis modiolaris as restricted by Foerste is a. guide fossil of the Pulaski shale in New York and in the corresponding hori- zons southward in the Appalachians and west to the Ohio Valley. Occurrence—MarTINSBURG SHALE (Fairview division). Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Penn- sylvania. Collections —Maryland Geological Survey, U. 8S. National Museum. 19 288 SYSTEMATIC PALEONTOLOGY Genus MODIOLODON Ulrich MopDIOLODON TRUNCATUS (Hall) Plate LVI, Vig. 25 Modiolopsis truncatus Hall, 1847, Pal. New York, vol. i, p. 296, pl. 1xxxi, figs. 3a, b. Modiolopsis truncatus Hall and Whitfield, 1875, Geol. Surv. Ohio, Pal., vol. ii, p. 86, pl. ii, fig. 13. Modiolodon truncatus Ulrich, 1893, Geol. Surv. Ohio, vol. vii, p. 656, pl. li, figs. 9, 10. Description.—“ Shell below the medium size; shortly ovate in outline, the widest part being about one-third of the entire length from the posterior end. Valves compressed, or depressed convex, most prominent near the center. Beaks small and closely compressed, scarcely projecting beyond the line of the hinge. Anterior margin rather shortly rounded, the extremity extending but little beyond the beaks; basal margin gently and regularly curving; posterior end more broadly rounded than the anterior and most abruptly at the postero-basal portion; above, it slopes more gradually backwards to the extremity of the hinge line, with which it unites without forming any perceptible angle. “ Surface of the valves marked by irregular, rather strong, concentric lines of growth. “The internal casts—the condition in which the species is usually found in the softer parts of the formation—show a large, elongate pos- terior muscular scar, situated a little within the postero-cardinal margin, and parallel with it; also a smaller lunate anterior scar, and an entire pallial line.”—Hall and Whitfield, 1875. Occurrence—MarTINSBURG SHALE (Fairview division). Tuscarora Mountain, one and: one-half miles southeast of McConnellsburg, Pennsyl-- vania. Pulaski shale near Rome, New York. Collection.—U. 8. National Museum. MarYLAND GEOLOGICAL SURVEY 289 Genus ORTHODESMA Hall and Whitfield ORTHODESMA NasuTUM (Conrad) Plate LVIII, Fig. 1 Cypricardites nasuta Conrad, 1841, 5th Ann. Rept. New York Geol. Surv., p. 52. Modiolopsis nasutus Hall, 1847, Pal. New York, vol. i, p. 159, pl. xxxv, iad 7, p. 296, pl. Ixxxi, fig. 2. Orthodesma nasutum Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, p. 286, pl. iii, fig. 5; pl. 5, fig. 3. Description.—This well-marked species is easily distinguished from all associated pelecypods by its narrow, subelliptical form and its anterior extremity drawn out into a narrow, quite extended nasute form. The cardinal margin of the shell is distinctly straight posterior to the beak, but anterior to it the margin drops so that at its greatest departure it is at least 3 mm. lower. In its anterior portion the shell is depressed and this, in connection with the outline, adds to the nasute appearance. Posterior to the beak the shell is more convex with the areas of greatest convexity near the cardinal margin. The surface is marked by indistinct concentric striations which are plainest along the basal margin of the anterior part. The type specimens were secured from the Pulaski shale division of the Lorraine at Lorraine, near Rome, etc., New York. Occurrence.—MartiNsBurG SHALE (Fairview division). Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Penn- sylvania. Collection.—U. S. National Museum. crass GASTROPODA Order ASPIDOBRANCHIA Family PLEUROTOMARIIDAE Genus PLEUROTOMARIA Defrance PLEUROTOMARIA ? CANADENSIS Billings Plate XXXVI, Figs. 4, 5 Pleurotomaria canadensis Billings, 1865, Pal. Fossils, vol. i, Geol. Surv. Canada, p. 230, figs. 214, a, b. 290 SYSTEMATIC PALEONTOLOGY Description.—Shell large, lenticular 35 to 60 mm. in diameter, consist- ing of six somewhat slender whorls rising into a depressed conical spire. Inner two-thirds of whorls gently convex; suture distinct. Margin of whorls sometimes acute and turned upwards, sometimes with a rounded band. Just within the margin is a wider concave band. Umbilicus wide, one-half to two-thirds the shell diameter, with margin subangular, and the inner slope of the whorls generally flat. A slight concave band just beneath the margin on the under side of the whorls. Aperture trans- versely ovate or rhomboidal with the outer and inner angles acute. Sur- face with fine, sharp, unequal striae, usually with shallow undulations 2 to 4 mm. wide conforming to the coarse of the striae; all curving back- wards to the margin and reaching it at an acute angle. . Occurrence—BEBKMANTOWN LimEsToNnE (Ceratopea zone). Near McConnellsburg and other localities in southern Pennsylvania and east of Williamsport and near Halfway, Maryland. Collection.—U. 8S. National Museum. PLEUROTOMARIA ? GREGARIA Billings Plate XXXV, Figs. 1-3 Pleurotomaria gregaria Billings, 1859, Canadian Nat. Geol., vol. iv, pp. 355, 358, figs. 8h-k. : Description.—Shell small, 8 mm. long and 5 mm. wide; spire conical with an apical angle of about 45°; three or four whorls. A narrow spiral band is present. On the body whorl, the band is somewhat above the middle of the volution, but in the upper whorls it is situated on the lower outer side at about one-fourth the height. An obscure carina on the body whorl, just above the spiral band, and another close to the suture is present on mature examples; the intervening space is flat or slightly con- cave. Below the band is a third carina, scarcely visible, and below this the whorl is rounded ventricose. There is a small umbilicus. Surface minutely striated. This is an interesting and well-marked species, but until a complete revision of Beekmantown gastropods is made, its generic position must remain very uncertain. MaryLAnp GEoLocicaL SURVEY 291 Occurrence-—BEEKMANTOWN LimEstoneE (Turritoma zone). Stouf- ferstown, Pennsylvania, and east of Huyett, Maryland. Collection.—U. 8S. National Museum. PLEUROTOMARIA ? FLORIDENSIS Cleland Plate XXXI, Fig. 6 Pleurotomaria floridensis Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 125 (253), pl. xv, fig. 12. Description.—Shell quite small, 3 mm. wide at the base and 4 mm. high, consisting of five slightly rounded volutions, conical, with an apical angle of 44° and a minute umbilicus. Imperfect casts and cross-sections in the rock of a small conical shell found occasionally in the Stonehenge limestone of Maryland seem to be representatives of this interesting species which hitherto has been noted only in the corresponding horizon in New York. The reference of this species to Plewrotomaria is known to be incorrect, but in the present state of our knowledge of Canadian gastropods it is useless to attempt more accurate generic determination. The specimens found in Maryland are not well enough preserved for a critical study of their generic characters. Occurrence.—BEEKMANTOWN LIMESTONE (Stonehenge member). Vicinity of Hagerstown, Maryland. Tribes Hill limestone of New York. Collection.—U. 8. National Museum. Genus HORMOTOMA Salter HorMOTOMA ARTEMESIA (Billings) Plate XXXVI, Figs. 8, 9 Murchisonia artemesia Billings, 1865, Pal. Fossils, vol. i, Geol. Surv. Canada, p. 345, fig. 332. Description.—Shell elongate, varying from 50 to 75 mm. in length, slender, consisting of 10 to 12 depressed convex whorls with a strong, rounded spiral band. In casts the whorls are depressed ventricose, flattened in the middle and abruptly rounded in the deep suture. Casts of the exterior show a strong, rounded band along the median line of the 292 SYSTEMATIC PALEONTOLOGY whorls about 2 mm. wide on the large whorls. Surface with fine, sharp striae curving backwards to the band. The elongate, slender form of this shell and the band along the median line of the whorls are sufficient characters to discriminate it from other associated forms of gastropods. Occurrence.—BEEKMANTOWN LimeEstonn (Ceratopea zone). Appa- lachian Valley in Pennsylvania, Maryland, and Virginia. Natural sections and poorly preserved casts of this species occur in the exposures east of Williamsport and in the vicinity of Halfway, Maryland. Collections —Maryland Geological Survey, U. S. National Museum. HorMoroMa GRACILIS (Hall) Plate LV, Figs. 7, 8 Murchisonia gracilis Hall, 1847, Pal. New York, vol. i, p. 181, pl. xxxix, figs. 4a-c; p. 303, pl. lxxxiii, figs. la-b. Hormotoma gracilis Ulrich and Scofield, 1897, Geol. Minnesota, vol. iii, pt. 2, p. 1015, pl. 1xx, figs. 18-21. Description (typical form) .—“ Height 20 to 33 mm., apical angle very constantly about 18°. Shell small, slender; volutions about 14 in a length of 30 mm.; rounded generally with a slight angulation, on which lies the band, a little beneath the middle; band seldom preserved, when perfect, rather narrow, smooth, flat or faintly concave and margined on each side by a delicate raised line; suture simple, deep; lines of growth fine, bending strongly backward from the suture to the band, and beneath this curving very strongly forward again, the whole indicating a deeply notched mouth ; aperture a little higher than wide, rounded except below where it is somewhat produced; inner lip reflected, forming a slightly twisted and thickened columella.”—Ulrich and Scofield, 1897. Widely distributed in the United States and Canada in rocks ranging from the Trenton to and through the Richmond. Occurrence—Martinspura SHaLe (Eden division). Fort Loudon, Pennsylvania, and the west slope of Rickard Mountain, Washington County, Maryland. Collecttons.—Maryland Geological Survey, U. 8. National Museum. MaryLAND GEOLOGICAL SURVEY 293 HorMoroMA GRACILENS (Whitfield) Plate XX XV, Figs. 4, 5 Murchisonia gracilens Whitfield, 1889, Bull. Amer. Mus. Nat. Hist., vol. ii, p. 53, pl. viii, figs. 14, 15. Description.—Shell rather small, possibly reaching 25 mm. in length, and very slender with the apical angle not more than 16 to 18 degrees, consisting of numerous whorls, six of which occur in the upper part of the spire of a small individual in 6 mm. Volutions ventricose, smooth or with but a very slight angularity near the middle of the exposed portion ; sutures deep and strongly marked. Columella and aperture unknown. This species is probably the Canadian representative of the abundant Middle and Upper Ordovician Hormotoma gracilis Hall which it greatly resembles. The earlier species, however, is a trifle more slender. Occurrence.—BEEKMANTOWN LIMESTONE (Turritoma zone). Stouf- ferstown, Pennsylvania, and near Huyett, Maryland. Collections.—Maryland Geological Survey, U. S. National Museum. Genus TURRITOMA Ulrich TURRITOMA ACREA (Billings) Plate XXXV, Fig. 11 Murchisonia acrea Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 232, text fig. 216. Description.—Shell rather small and slender, about.25 mm. long and 7 mm. at its widest portion, resembling a Turritella; apical angle 15° to 20°; whorls 12 to 15 in number, flat or subconcave, each with the lower edge angularly rounded and projecting slightly over the one below; surface above this projection flat or gently concave; and sloping to the suture, near which is a slight convexity. Surface characters unknown. This shell is easily recognized even in poor specimens by its consider- able resemblance to a small species of Turritella. Its characters are so distinctive that Ulrich selected it as the type of his genus Turritoma. 294 SYSTEMATIC PALEONTOLOGY Occurrence—BEEKMANTOWN LIMESTONE (Turritoma zone). Stouf- ferstown, Pennsylvania, and east of Huyett, Maryland. Canadian (Division G of the Quebec group), Port aux Choix, Newfoundland. Collection.—U. 8. National Museum. Genus LOPHOSPIRA Whitfield LopHospPira BICcINCTA (Hall) Plate XXXIX, Figs. 1-5 Murchisonia bicincta Hall, 1847 (not McCoy, 1844), Pal. New York, vol. i, p. 177, pl. xxxviii, figs. 5a-f (? 5g and 5h). Lophospira bicincta Ulrich and Scofield, 1897, Geol. Minnesota, Pal., vol. iii, pt. 2, p. 964, pl. Ixxii, figs. 1-5. Description.—“ Hight 15 to 30 mm.; apical angle 59° to 63°, usually about 60°. Volutions five or six, subangular; last one ventricose below, tricarinate, the upper ones bicarinate, the lower carina being hidden by the suture; central or peripheral angle margined on either side by a sharp elevated line, with a narrow groove between, the angle, therefore, being composed of three lines of which the central one is a little stronger and more prominent than the lateral ones; lower carina thin, abruptly raised, the space between it and the peripheral angle scarcely concave and almost perpendicular; upper carina sharp, rather strong, removed a little more than a third of the biconcave upper slope of the volution from the suture ; aperture somewhat obliquely subelliptical, higher than wide, narrow below, subangular at the lower inner corner ; inner lip but little thickened, slightly twisted, never completely covering the minute umbilicus; outer lip very slightly sinuate. Surface marked by fine, sharp, subequal striae, curving backward very gently from the suture to the peripheral band; beneath the latter they pass in a vertical direction to the lower carina which scarcely interrupts their course to the umbilicus, near which only a slight backward curve is noticeable. On the most perfect specimen seen all the transverse lines present the appearance of being minutely papillose or toothed, while the central line of the peripheral band is crossed by straight lines, of which there are nearly twice as many in a given space as of those coming from above and below. MaryYLanp GEOLOGICAL SURVEY 295 “The most marked and important feature of this species is the exceed- ing shallowness of the sinus or notch in the outer lip. The essential characters of L. bicincta, as here identified and restricted, are (1) the ventricose whorls, (2) the sharp and regular lines of growth, and (3) the exceedingly shallow sinus in the outer lip and vertical direction of the surface striae from the peripheral band downward.”—Ulrich and Sco- field, 1897. Occurrence—Stones River Limestone. Old quarry at Chambers- burg, Pennsylvania, and south into Maryland. The original types are from the Trenton of New York, but the species is said to range from the Stones River to the Richmond. Collections.—Maryland Geological Survey, U. S. National Museum. LopHosPira (RUEDEMANNIA) LiRATA (Ulrich) Plate LV, Figs. 5, 6 Lophospira (? Seelya) lirata Ulrich, 1897, Geol. Minnesota, vol. iii, pt. 2, p. 998, pl. xxii, figs. 56-59. Ruedemannia lirata Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, p. 312. Description.— Hight 15 to 24 mm., apical angles 65° to 70°, the angle of the first three whorls usually a little wider. Volutions about five and a half, ventricose, the carinae not greatly interfering with the general roundness of their outlines. Peripheral band median, appearing lower on the whorls of the spire, very slightly prominent, trilineate; the lines of equal strength and elevation or the median one is a little weaker and not as sharply defined as the margined ones. About midway between the band and the suture lines a small ridge or carina divides the upper slope into two flat or slightly concave spaces. Nearly the same distance beneath the lower margin of the band in the typical form of the species we meet with the first and strongest of about eight revolving ribs... .. Umbilicus exceedingly small, sometimes closed by a slight overlap of the inner lip. Aperture subovate, rounded below and rather straight at the inner side. Lines of growth sharp, thread-like, regular, either fine and 296 SYSTEMATIC PALEONTOLOGY equal on all parts of a whorl or they may be farther apart with interpola- tions on the upper slope. The lunulae of the band are fine and regularly curved.”—Ulrich, 1897. Occurrence—MARTINSBURG SHALE (Hden division). Jordans Knob, one and one-half miles northeast of Fort Loudon; Tuscarora Mountain, two and one-half miles southeast of McConnellsburg ; and Cowan Gap, five miles northeast of McConnellsburg, Pennsylvania. -Fragmentary casts of this species were noted in the sandstone debris of the Upper Martins- burg on the west slope of Rickard Mountain, Washington County, Mary- land. Collection —U. S. National Museum. ~ Genus LIOSPIRA Ulrich and Scofield Liospira MICULA (Hall) Plate LVIII, Figs. 7-9; Plate LV, Figs. 25, 26 Pleurotomaria micula Hall, 1862, Geol. Rept. Wisconsin, p. 55, fig. 1. Liospira micula Ulrich'and Scofield, 1897, Geol. Minnesota, vol. iii, pt. 2, p. 994, pl. Ixviii, figs. 24-29. Description.—Shell discoidal and small, rarely exceeding 16 mm. in diameter and usually 11 or 12 mm., with the umbilicus filled by a reflexed callosity of the inner lip. Externally this filling is concave, smooth and distinct from the finely striated under side of the volutions. The shell has four volutions with such shallow sutures that the spire forms an almost even slope from its apex to the periphery. Surface marked with fine lines of growth and in the best preserved specimens with very delicate revolving lines. On the under side the lines of growth are broadly curved with the greatest curvature on the inner half. The band is obliquely placed on the periphery and most visible on the upper side. This is one of the long ranging gastropods, specimens apparently the same as the types, which come from the Richmond (Maquoketa) of Wis- consin, being found in all the formations from the Trenton to and through the Richmond. The usual specimens found are seldom well preserved and it is possible. that with better material differences may be noted in examples from the various horizons. MaryYLAnD GroLogicaL SURVEY 297 Occurrence—MartixspurG SHALE (Eden and Fairview divisions). Jordans Knob, one and one-half miles northeast of Fort Loudon, Penn- sylvania, and the west slope of Rickard Mountain, Washington County, Maryland, have afforded poorly preserved specimens. Collection.—U. 8. National Museum. Family EUOMPHALIDAE Dekoninck Genus MACLURITES Lesueur MacLuRITES AFFINIS (Billings) Plate XX XIII, Figs. 8, 9 Maclurea affinis Billings, 1865, Pal. Fossils, vol. i, Geol. Surv. Canada, p. 238, text figs. 224a, b. Maclurea affinis Whitfield, 1897, Bull. Amer. Mus. Nat. Hist., vol. ix, p. 180, pl. iv, figs. 8, 9. Description.—Shell 35 to 50 mm. in width and 12 to 16 mm. in height with a flat spire of four or five slender whorls, uniformly convex on the upper side, and with deeply impressed sutures. Umbilicus about three- fifths the width of the shell, with the edge, as shown in a vertical sec- tion, acute; the inner sides of the whorls, in the umbilicus, convex. Sur- face unknown. Occurrence-—BEEKMANTOWN LIMESTONE (Cryptozoon steeli zone). Vicinity of Hagerstown and Williamsport, Maryland. Canadian ot Newfoundland and Vermont. Collection.—U. 8. National Museum. MAcCLURITES MAGNUS Lesueur Plate XXXIX, Figs. 12-15 Vaclurites magna Lesueur, 1818, Jour. Acad. Nat. Sci. Philadelphia, vol. i, p. 312, pl. xiii, figs. 1-3. Maclurea magna Halli, 1847, Pal. New York, vol. i, p. 26, pl. v, figs. la-e; pl. v, (bis), figs. la-c. Maclurites magnus Raymond, 1908, Ann. Carnegie Mus., vol. iv, p. 199, pl. 1, figs. 1, 2; pl. li, figs. 1, 2; pl. lii, figs. 1-4. Description.— Sinistrorsal, discoidal, depressed turbinate; breadth more than twice as great as the height; spire flat, a slightly depressed line 298 SYSTEMATIC PALEONTOLOGY at the sutures; whorls about six, gradually increasing from the apex, ventricose, flattened above, obtusely angular on the outer edge; surface marked by fine striae, which upon close examination, are found to be produced by the imbricating edges of lamellae; striae undulating, bending backwards from the suture and forward in passing over the edge of the shell; aperture obtusely trigonal, depressed above, slightly expanded beyond the dimensions of the whorl just behind it; axis hollow, umbilicus broad and deep, extending to the top of the spire.”—Hall. Associated with the large shell of this Maclurites is an operculum which undoubtedly belongs to the species. It is large, heavy, and horn- shaped and has the nucleus twisted to the right. In the inner right-hand corner of the operculum, as may be noted in fig. 15, of pl. XX XIX, there is a long process projecting downward into the shell and forming a place for attachment of muscles. Occurrence—Stones River Limestone (Middle division). Many localities in southern Pennsylvania; Pinesburg, etc., Maryland. An abundant and characteristic fossil of the Middle Chazyan from Montreal, Canada, to east Tennessee, the original types coming from the Lake Champlain area. In Tennessee the species is so abundant in the Lenoir limestone that this formation has been termed the Maclurea limestone. Collections—Maryland Geological Survey, U. 8. National Museum. Mac uritres sorpipus (Hall) Plate XXXVI, Figs. 1-3 Maclurea sordida Hall, 1847, Nat. Hist. New York, Pal. vol. i, p. 10, pl. iii, figs. 2, 2a. Description.—Shell subdiscoidal; consisting of two to two and a half slightly disconnected whorls rapidly increasing in diameter, strongly rounded on the upper side with deeply sunken apex, flattened on the lower side, and the peripheral edge rather sharply rounded. Aperture semicircular. Shell thick, the surface usually with only faint lines of growth, but sometimes strong, transverse striae, with more distant undulations. The transverse lines of growth curve forward on the lower flattened surface and backward on the rounded upper surface. MARYLAND GEOLOGICAL SURVEY 299 Occurrence.—BEEKMANTOWN LimxsTone (Ceratopea zone). Casts and section of the shall may be observed at this horizon west of Hagers- town, and also in several exposures east of Williamsport, Maryland. Beekmantown of New York and Vermont. Collection.—U. S. National Museum. MAcLuRITES OCEANUS (Billings) Plate XXXV, Figs. 7, 8 Maclurea oceana Billings, 1865, Pal. Fossils, vol. i, Geol. Surv. Canada, p. 237, text fig. 223a, b. Description.—Shell varying from 25 mm. to 100 mm. in diameter, consisting of four or five, rather slender whorls with an umbilicus measur- ing about half the whole width in the small specimens. Spire flat; the outer edge narrowly rounded; the suture deeply impressed in the usual specimens, casts of the interior, but compressed and thread-like: when the shell is preserved. Outer side of the body-whorl gently convex, and sloping to the edge of the umbilicus at an angle of from 60° to 70° with the plane of the flat side of the shell. Aperture a little less than half the whole width of the shell in height. Edge of umbilicus acutely rounded ; inner side of the whorls in the umbilicus gently convex, and somewhat sloping with the edge exposed to the apex. Surface unknown, but most probably finely striated. Occurrence.—BEEKMANTOWN LimEsTONE (Turritoma zone). Natural sections of this shell were noted in the exposures along the National High- way east of Huyett, Maryland. Canadian of Newfoundland. Collection.—U. S. National Museum. Genus CERATOPEA Ulrich CERATOPEA KEITHI Ulrich Plate XXXVI, Fig. 15 Operculum of ? Maclurea Bassler, 1909, Bull. Geol. Surv. Virginia, vol. iia, pl. xx, fig. 3. Ceratopea keithi Ulrich, 1911, Bull. Geol. Soc. Amer., vol. xxii, No. 3, p. 665. 300 SYSTEMATIC PALEONTOLOGY Description.—The above name has been employed for an unusual type of operculum supposed to belong to some spiral shell like Maclurea. The particular gastropod possessing such a thick closure to the shell is un- known. -Possibly the shell was of such a nature that it was easily de- stroyed, but the opercula occur often in considerable numbers. Several distinct types of these opercula are known, but each holds its own par- ticular form and marks a definite stratigraphic horizon. The one to which the name Ceratopea keitht has been given, marks a zone in the Middle Beekmantown throughout the Appalachian Valley, and as specimens are usually common, this species is regarded as such an exceptionally valuable guide fossil that the name Ceratopea zone has been applied to the strata containing it. The various aspects of the species are iilustrated in enough detail on pl. XXXVI to make its identification certain. Occurrence—BEEKMANTOWN LIMESTONE (Ceratopea zone). Several localities northeast and southwest of Halfway, Maryland, afford silicified specimens of this fossil. A common and characteristic fossil of the Middle Beekmantown in the Appalachian Valley from Pennsylvania to Alabama. Collections.—Maryland Geological Survey, U. 8. National Museum. Genus HELICOTOMA Salter HELICOTOMA PLANULATOIDES Ulrich Plate XLII, Figs. 13-15 Helicotoma planulatoides Ulrich, 1897, Geol. Minnesota, Pal., vol. iii, pt. 2, p. 1034, pl. Ixxiv, figs. 28-30. Description.—This species is closely related to the widespread Black River species Helicotoma planulata Salter, but differs in that it has only about four whorls instead of five and each descends slightly below the level of the preceding. The umbilicus is somewhat narrower than in H. planulata and revolving lines are totally absent. Specimens range in width from 15 to 25 mm. Occurrence.—CHAMBERSBURG Limestone (Tetradium cellulosum bed). Fort Loudon, Franklin County, Pennsylvania. Lowville limestone of Kentucky and Tennessee. Collection.—U. S. National Museum. MaryLanp GroLogicaL SURVEY 301 HELICOTOMA VERTICALIS Ulrich Plate XLII, Figs. 16, 17 Helicotoma verticalis Ulrich, 1897, Geol. Minnesota, Pal., vol. iii, pt. 2, p. 1035, pl. lxii, fig. 69; pl. lxxiv, figs. 18 and 19. Description.—This shell, although known only from casts of the in- terior, is so well characterized by the rectangular form of the outer and upper surfaces of the whorls that it should be easily recognized. The whorls are not more than four in number, enlarge rapidly, are strongly convex below and leave a deep and relatively narrow umbilicus. On the under side the cast resembles the shell of Helicotoma planulatoides quite closely, but otherwise the two species are quite different, as the outer side of the whorls in the latter are concave and inclined inward above instead of convex or flat and vertical. Occurrence.—CHAMBERSBURG LiImEsToNE (Tetradium cellulosum bed). Fort Loudon, Franklin County, Pennsylvania. Lowville lime- stone of Kentucky. Collection.—U. 8. National Museum. Genus EGCYLIOPTERUS Remele EcCYLIOPTERUS DisJuNCTUS (Billings) Plate XXXV, Figs. 9, 10 Ophileta ? disjuncta Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 344, text fig. 331a, b. Description.—Shell about 25 mm. in diameter, consisting of two or three whorls slightly separated from each other and with a strongly elevated, sharp carina. Spire deeply concave; carina located one-third the width from the outer margin. Within the carina there is first a shallow concave band, and then a concave slope into the suture; without it is a little defined concavity, below which the periphery is uniformly convex. The whorls on the under side vary from uniformly to depressed convex, sometimes becoming flat near the aperture along the median line. Depth and width of whorls about equal, greatest amount of separation of whorls about 4 mm. Surface with rather strong, scale-like striae. 302 SYSTEMATIC PALEONTOLOGY Occurrence—BEEKMANTOWN LIMESTONE (Turritoma zone). Stout- ferstown, Pennsylvania, and in exposures along the National Highway, east of Huyett, Maryland. Beekmantown limestone of Canada. Collection.—U. 8S. National Museum. EccyLIoPTERUS TRIANGULUS (Whitfield) Plate XX XIII, Figs. 6, 7 Ecculiomphalus triangulus Whitfield, 1890, Bull. Amer. Mus. Nat. Hist., vol. iii, p. 29, pl. i, figs. 5-9. Eccyliopterus triangulus Ulrich and Scofield, 1897, Geol. Minnesota, Pal., vol. iii, pt. 2, pl. Ixxiv, figs. 5, 6; pl. lxii, fig. 73. Description.—Shell less than two inches in diameter and consisting of from one to one and a half volutions, loosely coiled and not in contact at any point. Tube increasing rather rapidly in dimensions, triangular in section, flattened on three-fourths of its upper surface and rapidly rounded to the inner angle. Peripheral angle acute and the outer surface sloping rapidly inward to the rounded basal angle. Shell substance very thin, the surface characters unknown, except indistinct wavy lines cross- ing the shell and receding toward the acute angle. The apical portion is usually entirely filled with calcareous matter as the shell gets larger, thus shortening the inner coil of the casts. Occurrence.—BEEKMANTOWN LIMESTONE (Cryptozoon steeli zone). Three-fourths mile east of Charlton, Maryland, and at the same horizon in Pennsylvania. The types are from this formation m Vermont. Collection.—U. S. National Museum. Genus OPHILETA Vanuxem OPHILETA COMPLANATA Vanuxem Plate XX XI, Figs. 2-5 Ophileta complanata Vanuxem, 1842, Nat. Hist. New York, Geol., vol. iii, p. 36, fig. 2. Ophileta complanata Cleland, 1903, Bull. Amer. Pal., vol. iv, p. 15 (41). Pleurotomaria hunterensis Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 124 (252), pl. xvii, figs. 1, 2, 7, 8. Pleurotomaria hunterensis Cleland, 1903, Bull. Amer. Pal., vol. iv, p. 16, pl. iv, figs. 1, 2. MarYLAND GEOLOGICAL SURVEY 803 Description.—Shell conical, varying from 10 mm. to 40 mm. in width, consisting of six or more volutions elevated into a spire and with an umbilicus about one-half as wide as the entire diameter. Upper surface of shell nearly flat with a faint groove near the edge; under surface slightly angulate. Aperture irregularly rhomboidal. Under the name of Ophileta complanata a number of distinct species of Canadian gastropods has been classed in the past half century and it has only been by the study of specimens from the type localities in the Mohawk Valley that the real characters of the species have been identified. Vanuxem’s very imperfect description is as follows: “TO. complanata] consists of many convolutions resembling a single coil of cord formed on a flat surface, the diameter of the coil being usually about an inch. From analogy of formation it evidently pertains to the same genus with O. levata. It is more rare than O. levata, but is occa- sionally met with in the same localities on the Mohawk.” The type specimen of O. complanata appears to be lost, but as noted by Cleland, there is little doubt that the species described by him as Pleurotomaria hunterensis has usually been identified as O. complanata in the Mohawk Valley. Both names undoubtedly refer to the same species, especially since the occurrence of each is identical. Although Vanuxem’s description and figure are not sufficient for present-day pur- poses, it seems best to recognize his name on account of the generic term Ophileta. If the genotype O. complanata should not be recognized the widely quoted genus Ophileta too would have to be dropped. The synonymy is further complicated by the fact that Weller has based his genus Polygyrata on a species from New Jersey apparently closely related to Ophileta complanata. With regard to the numerous other references to supposed O. complanata, this is neither the time nor the place to discuss them. Only a monographic faunal study of the entire Canadian can clear up this complicated subject. Occurrence—BEEKMANTOWN Limestone (Stonehenge member). Vicinity of Hagerstown and Funkstown, Maryland. The type localities are in the Mohawk Valley of New York, Little Falls, Canajoharie, Tribes Hill, Ft. Hunter, etc., where the species occurs in the Tribes Hill division of the Canadian. Collections.—Maryland Geological Survey, U. 8. National Museum. 20 304 Systumatic PALEONTOLOGY OPHILETA LEVATA Vanuxem Plate XX XT, Figs. 18, 19 Ophileta levata Vanuxem, 1842, Nat. Hist. New York, Geol., vol. iii, p. 36, mae sore Cleland, 1903, Bull. Amer. Pal., vol. iv, p. 16. Ophileta discus Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 124 (252), pl. xv, figs. 5, 6. Description.—Shell discoidal, 10 mm. or less in diameter, consisting of four or more whorls rising into a slightly elevated spire, and concave on the lower side where the umbilicus is wide and shows all of the whorls. Margin of whorls sharp and somewhat elevated; upper side of whorl flat, lower side rounded. The identification of the specimens here referred to Ophileta levata is due to Cleland who by a comparison of type specimens of each has shown that his Ophileta discus and Vanuxem’s O. levata are based on the same species. As in the case of Ophileta complanata, Vanuxem’s descrip- tion and figure of O. levata are of little value. Occurrence.—BEEKMANTOWN Limestone (Stonehenge member). Vicinity of Hagerstown and Funkstown, Maryland. Abundant in the Tribes Hill limestone of the Canadian at Canajoharie, Tribes Hill, Fort Hunter and other localities in the Mohawk Valley of New York. Collection.—U. 8. National Museum. OPHILETA COMPACTA Salter Plate XXXITI, Figs. 1-3; Plate XXXIV, Fig. 2 Ophileta compacta Salter, 1859, Quart. Jour. Geol. Soc. London, vol. xv, p. 378, pl. xiii, fig. 12. Ophileta complanata Whitfield, 1889, Bull. Amer. Mus. Nat. Hist., vol. ii, p. 48, pl. vii, figs. 18-25. Description.—Shells discoidal, coiled in the same plane; flat or slightly concave below, more concave above. Periphery flattened obliquely, the lower edge of the volution being the largest, and rounded to the base, while the upper angle is sharply carinate. Upper surface of each volution MARYLAND GEOLOGICAL SURVEY 305 obliquely sloping to the volution within it, giving the depressed spire. Aperture trapezoidal. Substances of the shell thick, the surface trans- versely striated on the top and below, with frequent strongly marked undulations on the flattened side and back of the volution. The above description is based upon fairly well preserved examples of this species from the Beekmantown of the Champlain Valley, described and illustrated by Whitfield as Ophileta complanata. Typical Ophileta complanata is quite a different shell, as can be noted by a comparison of the figures on plates XX XI and X XXIII. Occurrence.-—BEEKMANTOWN LIMESTONE (Cryptozoon steeli zone). Poor casts in the rock or in the form of natural sections. Hagerstown, etc., Maryland and various localities in Pennsylvania. Collection.—U. S. National Museum. Genus ECCYLIOMPHALUS Portlock EccYLIOMPHALUS MULTISEPTARIUS Cleland Plate XXXI, Figs. 20, 21; Plate XXXIV, Figs. 3, 4 Ecculiomphalus multiseptarius Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 123 (251), pl. xv, figs. 1-4. Ecculiomphalus multiseptarius Cleland, 1903, Bull. Amer. Pal., vol. iv, p. 17. Description.—The shell of this species is discoid and consists of two or more loosely coiled, slender volutions which gradually expand until the outer portion is 6 mm. in diameter in a specimen of 20 mm. width. In transverse section the outer coil of the shell is subovate and slightly carinated on the outer edge. The specific name refers to the partitions shown in natural section of the shell which give it the aspect of a cephalopod, but the curvature and the irregularity of these partitions will distinguish them from septa. Such partitions are known in other species of the genus and indeed form a generic character. They are especially well developed in the present species. Occurrence.—BEEKMANTOWN LIMESTONE (Stonehenge member). Rare in both the lower and upper divisions of the Stonehenge member 306 SYSTEMATIC PALEONTOLOGY at several localities in the vicinity of Hagerstown, Maryland. Natural sections of this sheli can be seen in the lower Stonehenge quarries and especially in the fences along the National Highway, one-fourth to one- half mile south of Funkstown, Maryland. Not uncommon in the Tribes Hill formation of the Canadian near Fort Hunter, New York. Collection.—U. 8. National Museum. EccYLIOMPHALUS TRENTONENSIS (Conrad) Plate L, Figs. 19, 20 Cyrtolites trentonensis Conrad, 1842, Jour. Acad. Nat. Sci., Philadelphia, vol. viii, p. 270, pl. xvii, fig. 4. Cyrtolites trentonensis Hall, 1847, Pal. New York, vol. i, p. 189, pl. xla, figs. 3a-d. Eccyliomphalus trentonensis Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 184, pl. xii, figs. 20, 21. Description.—Shell consisting of less than one volution, increasing gradually in size from the apex, coiled in one plane. Cross-section angularly subovate. Ventral side of the shell convex from the periphery to the inner margin; the periphery rather sharply rounded ; about mid- way between it and the inner margin, on the dorsal side of the shell, is an angular, subcarinate ridge, the space between this ridge and the peripheral angulation being nearly flat; from the dorsal ridge to the inner margin of the shell the surface is convex. The surface is marked by rather obscure and irregular lines of growth, which, on the dorsal side, slope backward to the dorsal ridge, thus indicating the presence of an angular sinus in the aperture at that point. The most complete specimen observed has a length of about 35 mm. around the periphery of the shell from apex to aperture.” —Weller, 1903. Occurrence—MarTINSBURG SHALE (Sinuites bed). Carlisle, Cham- bersburg and two miles south of St. Thomas, Pennsylvania. The Lower Trenton rocks of New York and New Jersey likewise have furnished specimens. Collection.—U. S. National Museum. MARYLAND GEOLOGICAL SURVEY 307 Family RAPHISTOMIDAE Genus RAPHISTOMA Hall RAPHISTOMA ? oBTUSUM Cleland Plate XX XI, Figs. 15-17 Raphistoma obtusa Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 125 (253), pl. xv, figs. 7-9. Description.—Shell averaging 10 mm. in width, convex above, much compressed and consisting of three volutions, forming an apical angle of 130°. Umbilicus about one-third the shell diameter, with angular margins. Upper surface of volutions compressed, outer edge acute, and inner edge rounded. The compressed form, angular margin, and few volutions of this shell will distinguish it from associated species. Occurrence—BEEKMANTOWN LIMESTONE (Stonehenge member). Several localities around Hagerstown and Funkstown, Maryland. Tribes Hill limestone of New York. Collection.—U. 8. National Museum. RaPHISTOMA ? COLUMBIANUM Weller Plate XXXI, Figs. 22, 23 Raphistoma columbiana Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 128, pl. iv, figs. 3-5. Description.—Shell nearly smooth, consisting of about three and one- half volutions, flat above and rounded below, which form a slightly elevated spire and have a small umbilicus below. Outer edge of shell sharply rounded and slightly elevated above. The outer volution has 2 broad, ill-defined sulcus just below and paralleling the periphery. The type specimen measures 13 mm. in diameter and 6.5 mm. in height. Occurrence.—BEEKMANTOWN Limestone (Stonehenge member). Hagerstown, Maryland. The types are from the Kittatinny limestone of New Jersey. Collection.—U. S. National Museum. 308 SYSTEMATIC PALEONTOLOGY Genus RAPHISTOMINA Ulrich and Scofield RAPHISTOMINA LAURENTINA (Billings) Plate XXXVI, Figs. 6, 7 Pleurotomaria laurentina Billings, 1859, Canadian Nat. Geol., vol. iv, p. 354, fig. 6. Description.—Shell 25 to 50 mm. in diameter, lenticular with depressed spire consisting of five or six whorls slightly convex on their upper sides, but with a shallow concave band just within their outer margin. Lower side of body whorl somewhat concave just beneath the margin, theu moderately convex to the umbilicus within which it is rather narrowly rounded. Umbilicus deep and about one-fourth the diameter of the shell. The cast of the interior exhibits an acutely rounded margin, which, owing to the concave band above, appears to be turned a little upward, or to have a narrow ridge all around on its upper side. Aperture subrhomboidal, somewhat indented by the adjacent whorl. The Appalachian Valley specimens are poorly preserved, but agree in all essential details with the figures of the Canadian specimens published by Billings. Occurrence—BEEKMANTOWN LIMESTONE (Ceratopea zone). Stouf- ferstown, Pennsylvania, and east of Williamsport, Maryland. Collection.—U. S. National Museum. Genus OMOSPIRA Ulrich OMOSPIRA ALEXANDRA (Billings) Plate XLITI, Figs. 16, 17 Murchisonia alexandra Billings, 1865, Geol. Surv. Canada, Pal. Fossils, vol. i, p. 172. Omospira alexandra Ulrich and Scofield, 1897, Geol. Minnesota, vol. iii, pt. 2, p. 946, pl. 1xx, figs. 66, 67. Description.—* Shell rather large, turbinate, acutely conical; apical angle from 45° to 50°; whorls about six, strongly ventricose, with a flat band in the upper third. The aperture appears to be large and ovate; MARYLAND GEOLOGICAL SURVEY 309 the inner lip is thin and folded over so as to conceal the minute umbilicus. Surface finely striated. Length about 30 lines; width of body whorl 15 lines. This species is about the size and somewhat of the shape of M. belli- cincta. The principal difference is in the form of the upper part of the whorl. The lower two-thirds or three-fourths of the whorl is nearly uniformly convex, but the upper third descends abruptly to the deep suture. The band is quite flat, and being situated on the upper sloping part, gives to the whorl a truncated appearance. The lower edge of the band is defined by a small acute carina, seldom visible in specimens which are worn.”—Billings, 1865. Occurrence-—CHAMBERSBURG LimESTONE (Tetradium cellulosum bed). Fort Loudon, Franklin County, Pennsylvania. Lowville limestone of Canada and Kentucky. Collection.—U. 8. National Museum. Family BUCANIIDAE Genus BUGANIA Hall BucaNnia SULCATINA (Emmons) Plate XXXIX, Figs. 6-8 Bellerophon sulcatinus Emmons, 1842, Geol. Nat. Hist. New York, vol. ii, p. 312, text fig. 4. Bucania sulcatina Hall, 1847, Pal. New York, vol. i, p. 32, pl. vi, figs. 10, 10a; pl. xxxiii, fig. 4d. Bucania champlainensis Whitfield, 1897, Bull. Amer. Mus. Nat. Hist., vol. ix, p. 181, pl. iv, figs. 14-16. Bucania sulcatina Raymond, 1908, Ann. Carnegie Mus., vol. iv, p. 194, pl. xlix, figs. 15-17; pl. 1, figs. 3, 4; pl. lv, figs. 13, 14. Description.—* Shell large, coiled in one plane, umbilicated on both surfaces, all the whorls visible. The whorls are broad, somewhat angular at the sides, the last whorl moderately expanded at the mouth. Shell on the whorls thin, but on the lip it becomes very thick and sometimes corru- gated. The surface is ornamented by coarse wavy revolving striae which are crossed by transverse lines of growth. 310 SYSTEMATIC PALEONTOLOGY “These lines turn backward in crossing the middle of the shell and then forward again on either side. Along the center of the shell runs a narrow carina or slit band which is open for a short distance on the last whorl. The lip shows a broad, deep notch on the outer edge, and at the base of this notch is a further slit. On most specimens this carina is a flat or depressed band, but on a few, especially on young specimens and on the outer whorl of adults, the carina is elevated.””—Raymond, 1908. This well-known Chazyan fossil is easily recognized by the shape of the shell with a slit band, and especially by its characteristic reticulate surface markings. Occurrence—Stones River Limestone (Middle division). Examples have been collected at the old quarry at Chambersburg, Pennsylvania, and south along this band of outcrop into Maryland. Chazyan of the Lake Champlain area and Tennessee. Collections.—Maryland Geological Survey, U. 8. National Museum. Genus TETRANOTA Ulrich and Scofleld TETRANOTA OBSOLETA Ulrich Plate LV, Figs. 22-24 Tetranota obsoleta Ulrich and Scofield, 1897, Geol. Minnesota, vol. iii, pt. 2, p. 880, pl. Ixv, figs. 19-23. Description.—This species differs from other members of the genus, and especially from the genotype Tetranota bidorsata, in the fact that the revolving ridges are much less developed, particularly on the last volution. The central lateral pair is quite obsolete except on the inner volutions and even the central pair merely maintains the same strength relatively that it held in earlier stages. Interior casts of the mature shell exhibit a broad, comparatively low, and more or less distinctly grooved central ridge, beyond which the surface is first shallowly excavated and then gently convex to the lateral boundaries of the volutions which again are not angular but rounded. The exterior of the shell appears the same except that the ridges bordering the slit band seem thinner and sharper. MaryYLAND GEOLOGICAL SURVEY 311 Another point of difference from J. bidorsata is that the umbilicus is smaller and ‘less abrupt and the volutions more rounded on each side and therefore elongate, reniform in cross-section. In the Eden shales, speci- mens of this species average 20 mm. in height. Occurrence.—Martinspurg SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon; Tuscarora Mountain, two and one-half miles southeast of McConnellsburg; and Cowan Gap, five miles northeast of McConnellsburg. Collection.—U. S. National Museum. Family CYRTOLITIDAE Genus CYRTOLITINA Ulrich CYRTOLITINA NITIDULA (Ulrich) Plate L, Figs. 17-18 Cyrtolites nitidulus Ulrich, 1879, Jour. Cincinnati Soc. Nat. Hist., vol. ii, p. 12, pl. vii, figs. 7, 7a. Cyrtolitina nitidula Ulrich, 1897, Geol. Minnesota, Pal., vol. iii, pt. 2, p. 866, pl. Ixii, figs. 53-55. Description.—< Shell small, 6 to 8 mm. in diameter; volutions about two, rapidly increasing in size, the outer embracing quite a half of the inner ; dorsum blunt, thick, flattened in casts; sides gently convex to the edge of the umbilicus into which they descend at first rather abruptly, then gently, the ventral part spreading saddle-like over the inner volu- tion. Aperture subcordate, notched below; outer lip rather broadly. and deeply emarginated. Umbilicus about 3.5 mm. wide in a specimen 8 mm. in diameter, narrowly rounded at the edge. Surface of casts with distinct, subregular, retrally curved, transverse striae, averaging about five in 2 mm. on the sides and back. The striae continue over and are quite distinct and curved on the flattened dorsum or slit-band. On the latter some very fine revolving lines, about four in 1 mm., occur on the sides of the volutions. Greatest diameter of a large specimen 8.3 mm.; width of aperture 5.0 mm.; height of same 5.0 mm.”’—Ulrich, 1897. 312 SYSTEMATIC PALEONTOLOGY The form of the volutions, the slit-band, and the striate, almost lamellose, surface markings characterize this interesting shell which has hitherto been known only from the Trenton rocks of the Ohio Valley. Occurrence—MARTINSBURG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Trenton at Covington, Kentucky. Collection.—U. 8. National Museum. Genus MICROCGERAS Hall MIcROocERAS INORNATUM (Hall) Plate L, Figs. 21, 22 Microceras inornatus Hall, 1845, Amer. Jour. Sci. and Arts, vol. xlviii, a ea inornatus Meek, 1873, Geol. Surv. Ohio, Pal., vol. i, p. 147, pl. xiii, figs. 4a, b. Cyrtolites subcompressus Meek, 1873, Geol. Surv. Ohio, Pal., vol. i, p. 147 (under C. inornatus). Description.—Shell minute, the largest diameter being 1.25 mm. or less, consisting of two rapidly diminishing, volutions which form a spire equally depressed on either side and obtusely carinated or angular upon the back. The carina is most conspicuous near the aperture and gradu- ally becomes obsolete. The aperture is somewhat quadrangular and the surface is smooth. This shell occurs almost invariably in association with several species of Cyclora, similar minute or dwarfed gastropods of larger species such as Cyclonema or Lophospina. In themselves these shells are of little value as horizon markers and it is only in association with other species that they are useful. Waagen supposed the species of Microceras to represent “ embryonic volutions of bellerophontes,” but they are more likely dwarfed varieties or embryonic stages of some carinated genus such as Cyrtolites. Occurrence—MarTINsBuRG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Mohawkian and Cincinnatian rocks of the Ohio Valley, etc. Collections—Maryland Geological Survey, U. S. National Museum. MARYLAND GEOLOGICAL SURVEY 313 Family SINUITIDAE Genus SINUITES Koken SINUITES CANCELLATUS (Hall) Plate LV, Figs. 12-21; Plate L, Figs. 37-39 Bellerophon bilobatus Emmons (not Sowerby), 1842, Geol. New York, vol. ii, p. 392, fig. 6. Bellerophon cancellatus Hall, 1847, Pal. New York, vol. i, p. 207, pl. Ixxxiii, figs. 10a-c. Protowarthia cancellata Ulrich and Scofield, 1897, Minnesota Geol. Survey, Pal., vol. iii, pt. 2, p. 872, pl. lxiii, figs. 1-14. Protowarthia cancellata Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 175, pl. xii, figs. 3-5. Description.— “ Shell of medium size, subglobose, close coiled, with no umbilicus when the shell is preserved, but with a small one in the casts. In immature specimens the dorsum of the outer volution is rather sharply rounded, but with increasing age it becomes more broadly rounded, losing entirely the obscure carination of the younge: shells. Sinus shallow, rounded ; the lateral margins of the aperture on either side of the sinus regularly and rather gently convex. Aperture wider than high, subsemi- circular in outline. On the larger internal casts one or more rather broad and shallow, rounded, transverse, wrinkle-like depressions are frequently present near the aperture and parallel with the apertural margin. “ The dimensions of a large specimen are: Maximum diameter, 21 mm. ; width of aperture, 18 mm.”—Weller, 1903. A wide-spread species of the United States and Canada ranging from the Trenton to and through the Richmond. In Pennsylvania and Mary- land the species occurs at practically all the outcrops of the fossiliferous Sinuites bed and Eden divisions of the Martinsburg shale. Occurrence.—MarvtinspurG SHALE. The slopes of Rickard Mountain in Maryland have furnished casts of the species. Collections —Maryland Geological Survey, U. S. National Museum. 314 SYSTEMATIC PALEONTOLOGY SINUITES GRANISTRIATUS (Ulrich) Plate LV, Figs. 9-11; Plate L, Figs. 40, 41 Protowarthia granistriata Ulrich, 1897, Minnesota Geol. Survey, Pal., vol. lii, pt. 2, p. 870, pl. lxiii, figs. 28-30. Description.—* Shell scarcely reaching the medium size, closely coiled, leaving no umbilicus; center of dorsum raised into a low broad ridge, defined on each side by an obscure wide furrow; with age the outer boundaries of the latter increase gradually in distinctness, the back of the outer half of the last volution in the largest specimens presenting a flattened appearance ; but the central ridge, though decreasing somewhat in hight, continues to the aperture. In casts of the interior there is a small umbilicus, while the central ridge is nearly as on the shell itself. Aperture transverse, about twice as wide as high, the width generally equalling the hight of the shell; sinus wide, only moderately deep, the margin of the lobes bending rather sharply where the apertural margin is intersected by the faintly raised boundaries of the flattened dorsum. Except in the umbilical regions the test is thin. Out of nearly 30 speci- mens, only two preserve anything of the external layer. These show that it is marked by fine lines of growth and by very delicate revolving lines. All of the other testiferous examples preserve only the inner and middle layers, the latter appearing in every case quite smooth. Most of the specimens preserve what may be called a fourth layer. This seems to have been deposited by the inner mantle over the inner volutions, includ- ing the smaller half of the outer, while on each side it extends around the callous filling of the umbilicus. The whole of this layer is finely granu- lose, except the lateral extensions, and these are covered by wavy revolving striae. Hight of an average shell, 19 mm.; width of aperture, 19 mm.; median hight of same, 9.3 mm.; width of inner volution, 6 mm.; depth of sinus, 5 mm.; width of same, about 10 mm.”—Ulrich, 1897. This shell is related to the preceding Sinuttes cancellatus, but the latter species has a deeper sinus, a rounder back and no dorsal ridge nor obscure furrows. When well preserved, the difference in surface markings is also a distinguishing character. MaryYLanp GEoLogicaL SURVEY 315 The types are from the Eden shale of the Ohio Valley. In the Appa- lachian ‘Valley the species is known from the corresponding horizon in southern Pennsylvania, the upper part (Eden) of the Martinsburg shale, and also from the Sinuites bed. Occurrence.—MartinsBure SHALE. Jordans Knob, one and one-half miles northeast of Fort Loudon; Chambersburg; two miles south of St. Thomas, Pennsylvania ; Rickard Mountain, Maryland. Collection.—U. 8. National Museum. Family TROCHONEMATIDAE Genus STROPHOSTYLUS Hall STROPHOSTYLUS TEXTILIS Ulrich and Scofield Plate L, Figs. 31-36 Strophostylus textilis Ulrich and Scofield, 1897, Minnesota Geol. Survey, Pal., vol. iii, pt. 2, p. 1064, pl. Ixxxii, figs. 49-54. Description.— Shell rather small, 12 to 25 mm. high, 11 to 20 mm. wide, obliquely conical; apical angle 60° to 70°; whorls, in casts, three or four, in entire shells, six or seven, increasing quite regularly in size from the acute apex, almost uniformly rounded, often with several widely separated, deep, oblique constrictions; suture deep; aperture subovate, oblique; inner lip appearing thin in a ventral view, but when a part of the outer wall is removed it is seen that it forms a moderately thick columella with a spiral fold beginning near the lower angle. In young examples neither the fold nor a spiral furrow just above it is very distinct, while in some cases the whole inner lip appears to be simple and thin as in Holopea. Surface beautifully cancellated by subequal, fine, sharp, revolving and obliquely transverse lines, the network growing strong enough on the last whorl to be distinctly visible to the naked eye.”— Ulrich and Scofield, 1897. The graceful form and beautiful markings of this shell are features which aid in its ready recognition. Occurrence-—MARTINSBURG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Black River and Trenton of Minnesota, Missouri and Kentucky. Collection.—U. S. National Museum. 316 SYSTEMATIC PALEONTOLOGY Genus CYCLORA Hall CycLora minuTa Hall Plate L, Figs. 23-26; Plate LII, Figs. 10-12 Cyclora minuta Hall, 1845, Amer. Jour. Sci. and Arts, vol. xlviii, p. 294. Holopea nana Meek, 1871, Proc. Acad. Nat. Sci. Phila., p. 172. Cyclora minuta Meek, 1873, Geol. Surv. Ohio, Pal., vol. i, p. 152, pl. xiii, figs. Ta-e. Description.—Shell small, averaging 1.00 mm. in height, smooth, con- sisting of about three volutions which rapidly expand toward the mouth and form a moderately elevated spire. The upper two whorls are quite small and the shell is formed in large part by the third whorl. The aperture is round and well defined. This interesting minute species occurs literally by the million at certain Middle and Upper Ordovician horizons where usually all the associated shells are similar dwarfed or embryonic forms. Cyclora minuta possibly represents the very young stages of Cyclonema or Strophostylus, althougn its black corneous shell substance is quite different from either of these genera. Probably a closer assumption would be to consider them as embryonic forms of Holopea. The latter genus, however, is sparsely represented by individuals in the rocks in which Cyclora abounds. Common at many horizons and localities of the Mohawkian and Cin- cinnatian in the United States and Canada. In the Cumberland Valley, however, it has been found only in the lower portions of the Martinsburg shale, particularly in the Sinuites zone at the base. Occurrence—MarTINSBURG SHALE (Sinuites and Corynoides beds). Chambersburg, Pennsylvania; Williamsport, Maryland and Strasburg, Virginia. Collections.—Maryland Geological Survey, U. 8. National Museum. CYCLORA PARVULA (Hall). Plate L, Figs. 28-30 Turbo ? parvulus Hall, 1845, Amer. Jour. Sci. and Arts, vol. xlviii, p. 294. Cyclora ? parvula Meek, 1893, Geol. Surv. Ohio, Pal., vol. i, p. 154. Description.—“ Spire elevated, volutions about four, smooth; first whorl angulated upon the center towards the aperture; outer edge of the MARYLAND GEOLOGICAL SURVEY 317 aperture projecting downwards. Height of shell 1/15 of an inch.”— Hall, 1845. Although this species has not been figured heretofore and its descrip- tion was quite meager, there is no difficulty in distinguishing it from other forms of Cyclora because of the angulation of the first whorl towards the aperture. The other species of Cyclora have rounded whorls and may represent the young of such genera as Cyclonema or Hormotoma. The angulated whorl of Cyclora parvula would suggest its relationship to Lophospira or some similar genus. Common in association with Cyclora minuta Hall in the Mohawkian and Cincinnatian rocks at Cincinnati, Ohio, and many other localities. Occurrence-—MarRTINSBURG SHALE (Sinuites bed). Chambersburg, Pennsylvania, and Strasburg, Virginia. Collections.—Maryland Geological Survey, U. 8. National Museum. CYCLORA HOFFMANNI Miller Plate L, Fig. 27 Cyclora hoffmanni Miller, 1874, Cincinnati Quart. Jour. Sci., vol. i, p. 313, fig. 33. Description.—Shell minute, the average length being about 1.50 mm., consisting of an elongated spire made up of five or six volutions which are round and increase gradually in size. Whorls quite convex, with a deep suture; aperture nearly circular, directed slightly downward; sur- face smooth. This neat, elongate little species is usually found associated with Cyclora minuta and Microceras inornatum, and like them has little stratigraphic value. In the Appalachians, however, these species are known only in the Trenton portion of the Martinsburg shale. Occurrence—MAarTINSBURG SHALE (Sinuites bed). Chambersburg, Pennsylvania, and Strasburg, Virginia. Collections.—Maryland Geological Survey, U. S. National Museum. 318 SYSTEMATIC PALEONTOLOGY Order OPISTHOBRANCHIA Suborder PTEROPODA Family HYOLITHIDAE Genus HYOLITHES Eichwald HyYoLitHes communis Billings Plate XXV, Figs. 5-8 Hyolithes communis Billings, 1872, Canadian Nat., n. s., vol. vi, p. 214. Hyolithes communis Walcott, 1886, Bull. U. S. Geol. Surv., No. 30, p. 136, pl. xiv, figs. 3, 3a-c. Hyolithes communis Walcott, 1890, 10th Ann. Rep. U. S. Geol. Surv., p. 620, fig. 65, pl. xxvii, figs. 3, 3a-g. Description.—* This species attains a length of about 18 lines, although the majority of the specimens are from 10 to 15 lines in length. The ventral [dorsal] side is flat (or only slightly convex) for about two-thirds the width, and then rounded up to the sides. The latter are uniformly convex. The dorsum [ventrum], although depressed convex, is never distinctly flattened, as is the ventral [dorsal] side. The lower lip projects forward for a distance equal to about one-fourth or one-third the depth of the shell. In a specimen whose width is three lines, the depth is two lines and a half. “The operculum is nearly circular, gently but irregularly convex externally and concave within. The ventral [dorsal] limb is seen on the outside as an obscurely triangular, slightly elevated space; the apex of the triangle being situated nearly in the center of the operculum. The base of the triangle forms the ventral [dorsal] margin. This limb occupies about one-third of the whole superficies of the external surface. The remainder, constituting the dorsal [ventral] limb, is nearly flat, slightly elevated from the margin towards the center. On each side of the apex of the ventral [dorsal] limb there is a slight depression running from the nucleus out to the edge. On the inside there is an obscure ridge corresponding to each one of the external depressions. It is most prominent where it teaches the edge. These two ridges meet at the center and divide the whole of the inner surface of the operculum into two nearly equal proportions. Marybanp GeEoLocicaL SURVEY 319 “The surface of the operculum is concentrically striated. The shell itself in some of the specimens is covered with fine longitudinal striae, from five to ten in the width of a line. The shell varies in thickness in different individuals. In some it is thin and composed of a single layer, but in others it is much thickened by concentric laminae, and thus approaches the structure of a Salterella. There are also fine engirdling striae, and sometimes obscure subimbricating rings of growth.”—Billings, 1872. The above description with the emendation as to the ventral and dorsal sides given by Walcott, will serve for the recognition of the poor frag- ments found in the Maryland strata. Occurrence.—ANTIETAM Sanpstone. Eakles Mills, Maryland, and the same horizon in Pennsylvania. Collections.—Maryland Geological Survey, U. S. National Museum. Suborder CONULARIIDA Family TORELLELLIDAE Holm Genus SALTERELLA Billings SALTERELLA sp. Description.—Certain layers in the lower part of the Tomstown lime- stone have exhibited molds of small, hollow, slender shells with a striated surface. These show that the shell is composed of several hollow cones placed one within the other as in the genus Salterella. These remains are too imperfect for description or illustration, but they are interesting on account of their occurrence in the Tomstown limestone where fossils are exceedingly scarce. Occurrence.—Tomstown Limestonr. Several localities east and southeast of Waynesboro, Pennsylvania. Collection.—U. S. National Museum. 21 320 SYSTEMATIC PALEONTOLOGY Genus COLEOLUS Hall CoLEOLUS IOWENSIS James Plate XLIX, Figs. 22, 23 Coleolus iowensis James, 1890, Amer. Geol., vol. v, p. 355. Description.—This species has never been illustrated, but it has been known for many years as a very abundant fossil in the Maquoketa shale of Richmond age in Illinois and Iowa. It occurs here in great numbers associated with Cyclora minuta and similar small gastropod shells, as well as such minute pelecypods as Ctenodonta obliqua and Clidophorus. The shell layer is seldom preserved, the species occurring almost invariably as phosphatized casts of the interior. The surface markings of the outer shell are occasionally preserved as molds of the exterior in which it may be noted that the shell surface is smooth or sometimes very minutely annu- lated. The shell itself is an elongate, gradually tapering, straight or slightly curved cone, 15 to 20 mm. long and a millimeter in diameter at its widest portion. The diameter and length of different examples of the species vary considerably, indeed quite frequently these fossils occur only as broken fragments. ‘ Occurrence-—MarTINsBurG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Abundant in the Mohawkian and Cincinnatian rocks of Iowa, Illinois, and many other states, the types coming from the Maquoketa shale division of the Richmond group of Iowa. Collections.—Maryland Geological Survey, U. 8. National Museum. Family CONULARIIDAE Genus CONULARIA Miller CoNULARIA TRENTONENSIS Hall Plate L, Fig. 42 Conularia trentonensis Hall, 1847, Nat. Hist. New York, Pal., vol. i, p. 222, pl. lix, figs. 4a-f. Conularia trentonensis Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 188, pl. iii, figs. 7, &. Description.— Shell of medium size, pyramidal in form, quadrangular in cross-section, the sides diverging from the apex at an angle of about MARYLAND GEOLOGICAL SURVEY 321 25°. The sides slightly convex, the angles furrowed. Each side marked by a series of angular, transverse costae, which are directed obliquely forward toward the aperture from each lateral margin forming a rounded angle of about 130° at the median line; from two to four of these costae ¢ occupy the space of 1 mm., being closer together and finer near the apex of the shell and becoming progressively coarser towards the aperture. The furrows between the costae are wider than the ridges, rounded in the © bottom, and are crossed at right angles by fine raised bars joining adjacent costae, which are somewhat closer together than the costae themselves and not quite as high. “The dimensions of a specimen which is somewhat incomplete at the apex are: Length, 38 mm. ; diameter at aperture, 18 mm.”—Weller, 1903. Occurrence.—ManrtinsBurG SHALE (Sinuites bed). Five miles south- west of Chambersburg, Pennsylvania, and at Strasburg, Virginia. Tren- ton limestone of New York. Collection.—U. S. National Museum. cass CEPHALOPODA Subclass TETRABRANCHIATA Order NAUTILOIDEA Suborder HOLOCHOANITES Family ENDOCERATIDAE Genus CAMEROCERAS Gonrad CAMEROCERAS sp. Plate XX XVII, Fig. 10 . Description.—The thin slabs of Frederick limestone not infrequently exhibit subcylindrical bodies now composed of crystalline matter, which are supposed to represent the endosiphuncle of some species of Camero- ceras. With no other evidence it is impossible to identify the species of this cephalopod. ORR SYSTEMATIC PALEONTOLOGY Occurrence.—Freperick Limestone. Frederick, Maryland, and neighboring localities. Collection.—U. S. National Museum. Suborder ORTHOCHOANITES Family ORTHOCERATIDAE Genus ORTHOGERAS Breynius ORTHOCERAS PRIMIGENIUM Vanuxem Plate XXXII, Fig. 5 _Orthoceras primigenium Vanuxem, 1842, Geol. New York, 3d Dist., p. 36, Rete primigenium Whitfield, 1889, Bull. Amer. Mus. Nat. Hist., vol. ii, No. 2, p. 56, pl. x, fig. 1. Orthoceras primigenium Cleland, 1903, Bull. Amer. Pal., vol. iv, p. 14, pl. iii, figs. 8, 9. Description.—In spite of 15 or more references to this cephalopod, the species cannot yet be said to have been sufficiently described for accurate determination. Really this name has been employed for any gradually tapering, straight cephalopod of the Canadian in which the septa are thin, deeply concave, ‘and closely arranged. In the present case the same procedure has been followed, for the identification of this species in Mary- land has been based upon longitudinal sections in the rock showing no other characters than those just mentioned. However, it is believed that this identification will be found correct when specimens from the New York type localities are restudied, since Vanuxem’s type came from the Tribes Hill limestone and the Maryland examples are from the corre- sponding formation in that state. Occurrence.—BEEKMANTOWN LimEsToNE (Stonehenge member). Hagerstown, ‘Maryland, and vicinity. Collections. Maryland Geological Survey, U. 8. National Museum. MaryLanp GEoLoaicaL SURVEY 823 ORTHOCERAS ARCUOLIRATUM Hall Plate XLVIII, Fig. 22 Orthoceras arcuoliratum Hall, 1847, Pal. New York, vol. i, p. 198, pl. xlii, figs. 7a-c. Description.—< Slender, very gradually tapering to an acute point ; surface marked by strong and extremely arching or undulating annula- tions, and obscurely, by fine longitudinal striae; annulations about equalling the spaces between them ; outer chamber and aperture unknown ; section circular; siphuncle central. “The distinguishing features of this species are its slender form and extremely arched annulations, which, in half the circumference, ascend twice the width of the space between each annulation. All the other annulated species have the ridges less arched upon the back.”—Hall, 1847. Occurrence—_CHAMBERSBURG LIMESTONE (Greencastle bed). Green- castle, Pennsylvania. Trenton limestone of New York. Collection.—U. S. National Museum. ORTHOCERAS JUNCEUM Hall Plate LI, Figs. 4-7 Orthoceras junceum Hall, 1847, Pal. New York, vol. i, p. 204, pl. xlvii, figs. 3a-f. Orthoceras junceum Clarke, 1897, Minnesota Geol. and Nat. Hist. Surv., Pal., vol. iii, pt. 2, p. 790, Description. Slender, tereta-cylindrical, tapering very gradually; septa thin, distant from one-fourth to one-third the diameter; outer chamber deep; siphuncle small, central; section circtlar; surface finely striated transversely, but without longitudinal striae.”—Hall, 1847. This rather frequently quoted species has received no further study since Hall’s original description in 1847 and it is probable that many misidentifications of it have been made. However, fragments of an Orthoceras from the basal Martinsburg shale of southern Pennsylvania agree so well with typical specimens of O. junceum from the type locality that it is believed the present identification is correct. Occurrence—Martinspurc SuaLE (Sinuites bed). Chambersburg, Pennsylvania. Trenton limestone of New York. Collection.—U. S. National Museum. 24 SYSTEMATIC PALEONTOLOGY ORTHOCERAS TRANSVERSUM Miller Plate LV, Fig. 27 Orthoceras transversum Miller, 1875, Cincinnati Quart. Jour. Sci., vol. ii, ei transversum Miller, 1889, North Amer. Geol. Pal. p. 452, text fig. 755. Description.—“ Shell medium size, rather rapidly enlarging; septa strongly arched and distant about one-fourth or one-fifth the diameter of the shell; siphuncle excentric, its form not observed ; outer shell thin and marked by strong transverse lines, distant from 1-100th to 4-100ths of an inch in a specimen having a diameter at the large end of three-fourths of an inch. The distance between these lines seems to increase as the diameter of the shell increases, but their distance apart is not uniform in different specimens of the same size. About four or five of these trans- verse lines will mark the distance between the septa, though they do not seem to have any connection with the arrangement of the latter”— Miller, 1875. The well-marked transverse lines of this species cause its recognition to be quite easy. Occurrence—MartTInsBurG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania; and Rickard Mountain, Washington County, Maryland. Eden shale at Cin- cinnati, Ohio. Collection.—U. S. National Museum. ORTHOCERAS LAMELLOSUM Hall Plate LVIII, Figs. 5, 6 Orthoceras lamellosum Hall, 1847, Pal. New York, vol. i, p. 312, pl. lxxxvi, figs. 2a-e. Description.—Shell slender and gradually tapering ; septa distant from each other one-fifth to one-fourth of an inch and having a convexity about equal to their distance apart; siphuncle slightly excentric; surface apparently lamellose or subimbricate. MaryLAND GEOLOGICAL SURVEY 325 This seems to be a well-defined species since the specimens from southern Pennsylvania show no apparent deviation from Hall’s figures. Unfortunately these specimens are no better preserved than the types and it is impossible to add anything to the above description except ta record the occurrence in new localities. Occurrence—MartinspurG SHALE (Fairview division). Tuscarora Mountain, one and one-half miles east of McConnellsburg, Pennsylvania. Pulaski shale of New York. Collection.—U. 8. National Museum. Family CYCLOCERATIDAE Genus SPYROCERAS Hyatt SPYROCERAS BILINEATUM (Hall) Plate LI, Figs. 1-3 Orthoceras bilineatum Hall, 1847, Pal. New York, vol. i, p. 35, pl. vii, figs. 4, 4a. Orthoceras bilineatum Clarke, 1897, Geol. Minnesota, vol. iii, pt. 2, p. 786, pl. xlvii, figs. 20, 21; pl. liv, figs. 6, 7. Description.—Shell comparatively small, gradually expanding, sub- circular in cross-section. Surface smooth over the apical region; con- centric annulations then develop, very obscure at first, but increasing in strength, until they become strong, oblique, or undulating ridges which are broad and most conspicuous near the aperture. Like these annula- tions the interspaces, which are somewhat wider, also become broader toward the body-chamber. An average complete shell probably has a length of about 150 mm. with an apertural diameter of not more than 20 mm. Surface ornamented by coarse and fine vertical, elevated lines, crossed by extremely fine horizontal lines. Slight nodes or projections mark the crossing of the two sets of lines. The smooth portion of the shell near the apex exhibits the vertical lines in two simple series. With growth the lines increase in number and the alternation in size of the striae becomes less pronounced. The horizontal striae are quite delicate and often not visible at all. 326 SYSTEMATIC PALEONTOLOGY The sipho is small and nearly central. The septa are rather shallow, the sutures transverse, averaging 2.50 mm. apart and with no definite relation to the annulations. The latter sometimes being oblique are crossed by the sutures which, however, may occur within a furrow. Occurrence-—Martinspure SHALE (Sinuites bed). Chambersburg, Pennsylvania. Black River and Trenton of New York and Canada. Collection.—U. 8. National Museum. Family TROCHOLITIDAE Genus TROCHOLITES Conrad TROCHOLITES INTERNISTRIATUS (Whitfield) Plate XXXV, Fig. 14 Lituites internistriatus Whitfield, 1886, Bull. Amer. Mus. Nat. Hist., vol. i, p. 332, pl. xxix, figs. 5-8. Trocholites internistriatus Ruedemann, 1906, Bull. New York State Mus., 90, p. 479, pl. xxiv, fig. 2, text fig. 38. _ Description.—Shell of rather small size, being about 50 mm. in diam- eter, and consisting of between two and three volutions. Volutions very slightly compressed laterally, but nearly circular in general outline, with a rounded dorsal margin. Outer surface of volutions obliquely annulated . with the annulations best developed on the sides and rounded on the surface; in each case separated by concave interspaces of equal width. The annulations are directed strongly backward from the suture on the side of the shell, where they gradually die out and then become obsolete or nearly so on the dorsum. Shell substance thick, the surface on the undulations and between marked by strong, almost lamellose striae, following the direction of the undulations on the sides of the shell, forming a deep retral sinus on the dorsum indicating a deep sinus in the dorsal lip of the aperture. Interior of the shell as indicated in exfoliated speci- mens marked throughout by very fine, transverse, thread-like striae, directed almost across the tube and numbering about 30 in the space of 2.5mm. Septa about 2.5 mm. apart near the base of the outer chamber MARYLAND GEOLOGICAL SURVEY 827 and apparently rather deeply concave. Siphon near the inner margin of the tube and comparatively large. The few examples of this fine cephalopod discovered in Maryland do not preserve all the surface features mentioned above, but they agree in size and general outline. Occurrence—BEEKMANTOWN Limestone (Turritoma zone). Stouf- ferstown, Pennsylvania, and east of Huyett, Maryland. Fort Cassin, Vermont. Collection.—U. 8. National Museum. TROCHOLITES AMMONIUS Conrad Plate L, Fig. 43 Trocholites ammonius Conrad, 1838, 2d Ann. Rept. New York Geol. Surv., eee aes ammonius Hall, 1847, Pal. New York, vol. i, p. 192, pl. xlA, figs. 4a-k. Description.—“ Discoidal; volutions in the same plane, about four, rounded, slightly concave on the ventral side, gradually enlarging in size towards the aperture, which is slightly expanded; surface marked by lamellose irregular and oblique transverse striae or ridges, between and upon which are finer lamellose striae, covering the outer surface, and giving it a peculiar textural or netted appearance; striae meeting in an arch upon the back; septa direct, or slightly undulated on the dorsal side; outer chamber large; siphuncle ventral.”—Hall, 1847. Only a small and imperfect example of this beautiful coiled cephalopod has been noted in the Trenton fauna at the base of the Martinsburg shale. So far as it goes this specimen agrees with the well-known Trocholites ammonius of the New York Trenton. Occurrence.—MARTINSBURG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Trenton limestone of New York and Kentucky. Collection.—U. S. National Museum. 328 SYSTEMATIC PALEONTOLOGY Suborder CYRTOCHOANITES Family ACTINOCERATIDAE Genus GONIOGERAS Hall GoNIOCERAS CHAZIENSE Ruedemann Plate XLI, Fig. 19 Gonioceras chaziense Ruedemann, 1906, New York State Mus. Bull., 90, p. 494, pl. xxxvi, figs. 3, 4. Description. The natural section exposes the septa, which are closely arranged, there being 10 of them counted within the space of 20 mm.; each septum rises within the body of the shell to about the height of five cameras, forming broad and low saddles in the lateral flanges, and becom- ing slightly deflected backward towards the outer margin of the flanges. Their central portions are much thickened by secondary deposits. The outer conch, which according to Hall is also in the other species of Gonioceras excessively thin, is not preserved; the greatest width of the phragmocone, as indicated by the septa, is a little over 70 mm. The phragmocone appears to have been at least as rapidly expanding as that of G. anceps. The siphuncle is very large (its diameter 7 mm.), strongly nummuloidal, filled with organic deposits which leave open but a narrow endosiphotube. From the latter radiate horizontal tubuli as in the other congeners. We have not been able to ascertain the transverse section of the conch and the surface is unknown.”—Ruedemann, 1906. . Occurrence. CHAMBERSBURG LIMESTONE (Caryocystites bed). Fort Loudon, Franklin County, Pennsylvania. Middle Chazyan of New York. Collection.—U. 8. National Museum. Family OOCERATIDAE Genus OOCERAS Hyatt OOCERAS KIRBYI (Whitfield) Plate XXXII, Figs. 19, 20 Cyrtoceras kirbyi Whitfield, 1889, Bull. Amer. Mus, Nat. Hist., vol. ii, p. 57, pl. x, figs. 4-7. Cyrtoceras kirbyi ? Cleland, 1900, Bull. Amer. Pal. vol. iii, p. 181 (259), pl. xvii, figs. 3, 4. MARYLAND GEOLOGICAL SURVEY 329 Description.—Shell strongly curved and laterally compressed, increas- ing moderately in dimension with the length. Cross-section ovate, some- what more than three-fifths as wide as long, with the widest part within the median line and the narrowest at the dorsum, which is narrowly rounded. Septa deeply concave, somewhat numerous and closely spaced, 12 of the chambers near the outer part on the dorsal edge occurring in 25 mm. Siphon small and in contact with the shell at the dorsal margin. Living chamber comparatively long and apparently not constricted near the aperture. Surface of the shell without ornamentation and moderately thick. Occurrence.—BEEKMANTOWN LimMEsTONE (Stonehenge member). South of Funkstown, Maryland. Tribes Hill limestone of New York. Collection.—U. 8. National Museum. Genus GYRTOCERAS Goldfuss CYRTOCERAS GRACILE Cleland Plate XXXII, Figs. 3, 4 Cyrtoceras sp. Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 19, pl. xvii, figs. 5, 6. Cyrtoceras gracilis Cleland, 1903, Bull. Amer. Pal., vol. iv, p. 13, pl. iii, ie Get Weller, 1903, Pal. New Jersey, vol. iii, p. 131, pl. v, figs. 7, 8. Description.—Shell small, 12 mm. long and 8 mm. in diameter, slender, arcuate, oval in transverse section. Siphuncle small and placed near the ventral edge. Septa smooth, slightly concave, close together, with five to six occurring in 4 mm. | The shape and small size of this cephalopod and the closely arranged septa will distinguish it from other Canadian species. The species was based upon specimens from the Tribes Hill limestone at Fort Hunter, Tribes Hill, and Canajoharie, New York. The same or a very similar species occurs in the Canadian portion of the Kittatinny limestone at Columbia, New Jersey. In. Maryland, natural longitudinal and cross-sections of apparently the same species have been noted on the weathered surface of the lower Stone- henge limestone. 330 SYSTEMATIC PALEONTOLOGY Occurrence.-—BEEKMANTOWN LiMestonr (Stonehenge member). One-half mile south of Funkstown, and near Hagerstown. Collection.—U. 8. National Museum. CYRTOCERAS BEEKMANENSE Whitfield Plate XXXII, Figs. 1, 2 Cyrtoceras beekmanensis Whitfield, 1889, Bull. Amer. Mus. Nat. Hist., vol. ii, p. 57, pl. x, figs. 2, 3. Description.—Shell as usually observed, from 75 to 100 mm. in length and less than 25 mm. wide, little curved, the amount of curvature not amounting to more than 3 mm. in a length of 75 mm.; laterally com- pressed so that the lateral diameter is somewhat less than the dorso- ventral; slightly oval in cross-section. Septa numerous, 14 chambers occurring in 25 mm., little curved and of shallow depth. Outer chamber of shell long. Siphon unknown. Surface of shell apparently smooth. Occurrence.-—BEEKMANTOWN LimerstongE (Stonehenge member). National Highway, one-half mile south of Funkstown, Maryland. Collection.—U. 8. National Museum. CyRTOCERAS CAMURUM Hall Plate XLVITI, Fig. 21 Crytoceras camurum Hall, 1847, Pal. New York, vol. i, p. 196, pl. xlii, fig. 6. Cyrtoceras camurum Clarke, 1897, Geol. Minnesota, 3, pt. 2, p. 805, pl. lx, figs. 5, 6. Description.—Fragments of a curved cephalopod occurring in the strata just above the typical Christiania bed in the vicinity of Green- castle, Pennsylvania, are so similar to the New York lower Trenton species described as Cyrtoceras camurum by Hall that they are believed to be the same. In neither area have complete specimens been found, so that it is still impossible to give a full description of the species. Occurrence-—CHAMBERSBURG LIMESTONE (Greencastle bed). Green- castle, Pennsylvania. The type locality is the Trenton limestone at Middleville, New York, but this species has also been identified in the Black River rocks of Wisconsin. Collection.—U. 8. National Museum. MARYLAND GEOLOGICAL SURVEY 331 Genus CYRTOGERINA Billings CYRTOCERINA MERCURIUS Billings Plate XXXV, Fig. 13 Cyrtocerina mercurius Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 194, text fig. 179. Description.—Shell short, strongly curved and tapering abruptly; elliptical in section, the dorso-ventral diameter being one-third or one- fourth greater than the lateral. Measured on the surface of the ventral side near the living chamber the septa are about 1 mm. apart, but on the dorsal side near the apex they are probably closer together. Siphuncle in contact with the shell on its dorsal side. The dorsal position of the siphuncle, the close arrangement of the septa, and the strongly curved, abruptly tapering features are characters to aid in the recognition of this shell, although the species cannot be considered to be fully described as yet. Occurrence.—BEEKMANTOWN Limestonr (Turritoma zone). Stouf- ferstown, Pennsylvania, and east of Huyett, Maryland. Collection.—U. 8. National Museum. Family ONCOCERATIDAE Genus CYCLOSTOMIGERAS Hyatt CYCLOSTOMICERAS CASSINENSE (Whitfield) ? Plate XXXII, Figs. 6, 7 Gomphoceras cassinense Whitfield, 1886, Bull. Amer. Mus. Nat. Hist., vol. i, p. 322, pl. xxix, figs. 1-3. Cyclostomiceras cassinense Ruedemann, 1906, New York State Mus. Bull., No. 90, p. 50, fig. 56; pl. xxxvii, figs. 1-3; pl. xxxviii, figs. 5, 6. Description.—This species has been carefully described by Ruedemann to whose work of 1906 the student is referred for details and illustrations. The entire shell attains a size of about 100 mm. and a greatest width of 40 mm. The rate of growth is quite rapid, the living chamber is large, forming nearly half of the shell, the septa are shallow, and the siphuncle is large. Sections in the rock seen at several Maryland outcrops exhibit a cephalopod with the same rate of growth and other characters just 332 SYSTEMATIC PALEONTOLOGY mentioned, but better material is necessary before the determination can be made with certainty. Occurrence-—BEEKMANTOWN LimESTONE (Stonehenge member). Near Funkstown, Maryland. Cassin beds at Fort Cassin, Vermont. Collection.—U. 8. National Museum. ARTHROPODA ciass CRUSTACEA Subclass TRILOBITA Order HYPOPARIA Family HARPEDIDAE Genus EOHARPES Raymond EoHARPES OTTAWAENSIS (Billings) Plate LI, Fig. 11 Harpes ottawaensis Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 182, text fig. 165. Harpina ottawaensis Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 191, pl. xiv, figs. 1, 2. Harpina ottawaensis Raymond, 1905, Annals Carnegie Mus., vol. iii, p. 331, - pl. x, fig. 2. Eoharpes ottawaensis Ruedemann, 1912, New York State Mus., Bull. No. 162, p. 116, pl. ix, fig. 1. Description.—“ Head strongly convex, with a wide, punctured border which extends backward to about the thirteenth segment of the thorax. If a line be drawn across touching the posterior edge of the neck seg- ment, the contour in front of that line is nearly a perfect semicircle. Glabella regularly conical, its length about five-ninths that of the head; posterior furrows distinct, entering at about one-half the distance from the ocular ridge to the posterior margin of the neck segment, thence running obliquely inward and backwards at an angle of about 45°, apparently not quite one-third the width; two anterior furrows on each side, represented by obscure pits; neck furrow narrow; neck segment convex, strongly elevated on the fixed cheeks. The eyes (ocelli) are MaryYLAND GEOoLociIcaL SURVEY 333 small and situated on a line drawn across the glabella at the anterior fourth; ocular ridge well defined, smooth, prolonged, with a backward curve outside of the eye. Thorax a little more than half the width of the head; the axis strongly convex and gradually tapering backwards; side lobes flat; plurae with a wide groove along the middle, a small portion of their outer extremities turned backward. Surface of thorax, glabella and a subreniform space on each side of the base of the glabella smooth; the border with circular punctures about 0.2 mm. in width; the punctures large and more distant at the inner edge of the border; on the elevated part of the cheeks they have a subreticulated arrangement.”—Billings, 1865. This splendid species of which a nearly complete example has been described as above by Billings, is represented in the Trenton fauna at the base of the Martinsburg shale by fragments only, which, however, agree fairly well with the corresponding parts of the specimen figured by Billings and here reproduced on pl. LI. Occurrence—MarTINsBuRG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Trenton limestone of Ontario, New York and Minnesota. Collection.—U. 8: National Museum. Family TRINUCLEIDAE Genus CRYPTOLITHUS Green CRYPTOLITHUS BELLULUS (Ulrich) Plate LVI, Figs. 5, 6 Trinucleus bellulus Ulrich, 1878, Jour. Cincinnati Soc. Nat. Hist., vol. 1, p. 99, pl. iv, fig. 15. Description.—“ Body small, nearly flat, and symmetrical. Cephalic shield about three times as wide as long, subquadrate, with a distinct thoracic ring at the base, which is straight, with the posterior angles acutely angular or slightly rounded, and without any long spines; glabella prominent, pyriform and produced posteriorly, into a long spine, reaching to the pygidium ; cheeks not as prominent as the glabella, triangular, and finely punctate; marginal fillet wide, marked in front by from three to 334 SYSTEMATIC PALEONTOLOGY four rows of deep, rounded pores or punctures; the rows increase by im- plantation as they approach the posterior lateral margins, where they number from six to seven. “ The thorax consists of six articulations; axial lobe depressed, convex, narrow, and carrying on each side between the segments two rows of minute punctures ; lateral lobes flat, and three times as wide as the central lobe; pleura straight, and furrowed on the outer half. “ Pygidium small, acutely semi-elliptic, being about four times as wide as long, and broadly rounded in outline behind, with a raised and thick- ened margin ; axial lobe very small, and composed of four obscurely defined segments; lateral lobes each with three segments. “Length of largest known specimen, 6 mm.; length of cephalic shield, 3.5 mm.; breadth of do., 7 mm.; length of thorax, 1.25 mm.; breadth of do., 4.5 mm.; length of pygidium, 75 mm.; breadth of do., 4 mm.”— Ulrich, 1878. This interesting species is distinguished from all American and Euro- pean species of the genus in the straightness or slight concavity of the posterior edge of the cephalon, and in the relative flatness of the border. The thorax also is shorter and the neck spine longer. In young specimens such as the original type, these peculiarities are especially marked. In old examples the posterior edge of the cephalon turns somewhat pos- teriorly at the ends, but it is still much less curved than in all other species. Occurrence.—MARTINSBURG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Cowans Gap, five miles northeast of McConnellsburg, and Tuscarora Mountain, two and one-half miles southeast of McConnellsburg, Pennsylvania. Eden shale at Cov- ington, Kentucky. Collection.—U. 8. National Museum. CRYPTOLITHUS RECURVUS Ulrich n. sp. Plate LVI, Figs. 14-17 Description.—This new species has been discriminated by E. O. Ulrich, who has had the opportunity of studying a large number of foreign and American specimens of this genus. Cryptolithus recurvus differs from MARYLAND GEOLOGICAL SURVEY 335 the Trenton form usually identified as Cryptolithus tesselatus Green or Trinucleus concentricus Hall by the great width and decided posterior recurvance of the border and by its steeper slope, the cephalon as a whole being therefore more convex. C. concentricus resembles it in the last respect, but its border is of less width and has fewer rows of pits. Among the differences distinguishing the species from all the American species of the genus is the finely punctate and not reticulate marking of the glabella and lateral lobes. The type specimens figured were collected in the Eden shale at Coving- ton, Kentucky, and in the uppermost Trenton limestone at the same place. Occurrence —MartTINsBuRG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania. Collection.—U. S. National Museum. CRYPTOLITHUS TESSELATUS Green Plate LI, Figs. 19, 20; Plate LII, Fig. 17 Cryptolithus tesselatus Green, 1832, Monograph Trilobites North America, p. 73, cast 38, pl. i, fig. 4. Trinucleus concentricus Hall, 1847, Pal. New York, vol. i, p. 249, pl. xv, figs. 4a, ¢. Trinucleus concentricus Weller, 1903; Geol. Surv. New Jersey, Pal., vol. iii, p. 192, pl. xiv, figs. 3, 4. Description.—“ Head semi-circular or subcrescent-form in outline, the genal angles either destitute of spines or produced into long, slender, . straight spines. Glabella smooth, very prominent, ovoid in outline, the widest portion being in front, with a short, blunt spine posteriorly ; cheeks smooth, prominent, but depressed considerably below the glabella, from which they are separated by a well-defined dorsal furrow; eyes wanting. The entire anterior and lateral margins of the head are surrounded by a broad, somewhat flattened or concave border, which is marked in front by from three to five concentric rows of deep, rounded pits; one or two additional rows are introduced on the sides, and toward the genal angles the pits often become irregularly scattered. Length, 10 mm.; width, 15 mm. ; convexity, 6 mm.”—Weller, 1903. 22 336 SYSTEMATIC PALEONTOLOGY Several distinct species are doubtless included in the many descriptions that have been published under the name of Cryptolithus tesselatus and more particularly Trinucleus concentricus. The specimens from the base of the Martinsburg shale, however, are undoubtedly the same specifically as the Trenton forms upon which Green and Hall based their figures and descriptions. The New Jersey Trenton specimens described as above by Weller likewise belong to the same species. This species is generally quoted as ranging from the base of the Trenton to the middle part of the Maysville group, but the species when restricted will probably be found to be limited to the Trenton rocks. In Pennsylvania and southward it occurs in the Sinuites zone of the Trenton at the base of the Martinsburg shale. Occurrence—MarTINSBURG SHALE (Sinuites and Corynoides beds). Williamsport, Maryland, and Chambersburg, Pennsylvania. Collections.—Maryland Geological Survey, U. 8S. National Museum. Family RAPHIOPHORIDAE Genus AMPYX Dalman Ampyx (LoncHopoMAS) NoRMALIS (Billings) Plate XLV, Figs. 13, 14 Ampyz normalis Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 295, text fig. 286. Ampyx (Lonchodomas) normalis Grabau and Shimer, 1910, N. A. Index Fossils, vol. ii, p. 259. Description.—“ Head, without the movable cheek, triangular, the width about one-third greater than the length; fixed cheeks, gently convex, smooth; neck segment consisting of a flat plate, inclining backwards. The glabella elongate-ovate, greatest width about the mid-length, one- fourth narrower at the neck segment, the apex extending a little over the front margin of the head; the rostrum, apparently, when perfect, equal to the whole length of the head, not round but fluted ; two or three ovate or nearly circular scars, one each side of the glabella in the posterior half. “ Pygidium triangular, width twice the length, the two posterior sides MARYLAND GEOLOGICAL SURVEY 337 gently convex, and the margin abruptly bent down or bevelled nearly vertically, the upper edge of the bevel angular and with indications.of a slightly elevated linear rim; axis very depressed convex or nearly flat, its width at the anterior margin about one-fourth of the whole width, extending the whole length or nearly so, crossed by obscure undulating furrows. Side lobes gently convex. “ Length of the head without the rostrum, 5 or 6 lines; length of the pygidium about 4 lines.”—Billings, 1865. . Fragmentary specimens of an Ampyz from the Echinospherites bed of Maryland and Pennsylvania agree so closely with Billings’ figures and description that they are believed to represent the same species in spite of the differences in horizons. Occurrence.—CHAMBERSBURG LIMESTONE (Echinospherites bed). Southern Pennsylvania and at Pinesburg Station, Maryland. Collection.—U. 8. National Museum. Ampyx (LoncHopoMAs) HALLI Billings Plate XX XIX, Figs. 9-11 Ampyz haili Billings, 1862, Rept. Econ. Geol. Vermont, p. 231, text fig. 365. Ampyz halli Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 24, text figs. 25a-c. Lonchodomas halli Raymond, 1905, Ann. Carnegie Mus., vol. iii, No. 2, p. 332, pl. x, figs. 3-7. Description. Cephalon.—Cranidium triangular, the greatest width at the neck segment. The glabella extends about half its own length beyond the anterior angles of the fixed cheeks, and is then prolonged into a long, fluted spine, which curves gently upward. This spine is pris- matic, with a deep furrow on each of its four sides. The furrow on the upper side extends back to about the region of the fixed cheeks. Glabella widest at the anterior angles of the fixed cheeks, and contracting pos- teriorly, so that it forms about one-fifth of the whole width at the neck segment. On the cast there are two small nodes on each side of the glabella near its posterior end, one pair a little in front of the other. A distinct carina extends along the top of the glabella to the posterior end of the dorsal furrow on the rostrum. 338 SYSTEMATIC PALEONTOLOGY “ Thorax.—A specimen from Valcour Island retains the last two seg- ments of the thorax. They are narrow, extend horizontally, and on the pleura are deeply grooved. The fourth segment is 5 mm. wide, .3 mm. long and the axis is 1.6 mm. wide. The pygidium of the same specimen 1s 1.25 mm. long, 4.3 mm. wide, and the axis is 1.8 mm. wide at the anterior end. _ “ Pygidium.—The pygidium is about three times as wide as long, usually regularly rounded posteriorly, sometimes somewhat triangular. Axis wide, prominent, extending to the posterior end of the pygidium. The exfoliated axis shows seven to ten pairs of nodes very similar to those noticed by Ruedemann on specimens of Lonchodomas hastatus, from Rysedorph Hill. The pleura show three or four pairs of rather indistinct ribs. The margin is abruptly deflected all around.”—Raymond, 1905. This little trilobite is one of the common fossils of the Middle Chazyan (Crown Point) limestone of the Lake Champlain area, the types coming from Highgate Springs, Vermont. Occurrence—StTones River Limestone (Middle division). Penn- sylvania and Maryland. The old quarry at Chambersburg, Pennsylvania, has afforded a number of cephala with the long spines preserved. Collections.—Maryland Geological Survey, U. S. National Museum. Order OPISTHOPARIA Family CORYNEXOCHIDAE Angelin Genus DOLIGHOMETOPUS Angelin DoLicHOMETOPUS sp. Plate XXVI, Figs. 1-9 Description.—More or legs distorted cranida and pygidia of a probable new species of this genus of trilobites occurs in the basal part of the Elbrook limestone. Although the studies of this and allied species have not progressed far enough to warrant description, illustrations are intro- duced on pl. XXVI to show the varying aspect of such fossils under pressure. MaryYLAND GEOLOGICAL SURVEY 339 Occurrence-—E.LBrook Limestone. Small quarry on the eastern out- skirts of Waynesboro, Pennsylvania. Collection.—U. 8. National Museum. Family MESONACIDAE Genus OLENELLUS Hall OLENELLUS THOMPSONI (Hall) Plate XXIV Olenus thompsoni Hall, 1859, 12th Ann. Rept. New York State Cab. Nat. Hist., p. 59, fig. 1, p. 60. Olenellus thompsoni Walcott, 1886, U. S. Geol. Surv. Bull., No. 30, p. 167, pl. xvii, figs. 2, 4, 9; pl. xxii, fig. 1; pl. xxiii, fig. 1. Olenellus thompsoni Walcott, 1890, 10th Ann. Rept. U. S. Geol. Surv., pl. lxxxii, figs. 1, la; pl. Ixxxiii, figs. 1, la. Olenellus thompsoni Walcott, 1910, Smithsonian Misc. Coll., No. 53, p. 336, pl. xxxiv, fig. 9; pl. xxxv, figs. 1-7. Description.—* General form ovate, the length and breadth being nearly as six to five. Head broad lunate, with the postero-lateral angles much extended ; the width from the center to the outer margin of the eye almost equal to the width of the cheek. Eyes (which are much crushed in the specimen) elongate semi-oval, equal in length to the space between the anterior angles and the frontal margin; glabella distinctly lobed, narrower in front. “ Thorax with the lateral lobes about once and a half as wide as the middle lobe, consisting of 14 articulations, the third one of which is much longer than the others, and curving downwards with an extension reach- ing as far as the line of articulation of the seventh rib. The posterior articulations are bent abruptly backwards, so that the free extremities are parallel with the axis. Pygidium small, pointed, without visible rings and having a narrow ridge running down the center.”—Hall, 1859. Occurrence—ANTIETAM Sanpstony and Tomstown LiMEsToneE. Near Smithsburg, and at Eakles Mills in Washington County, Maryland. The type fossil of the Lower Cambrian in the eastern United States and Canada. Collections.—Maryland Geological Survey, U. 8. National Museum. 340 Systematic PALEONTOLOGY Family SOLENOPLEURIDAE Genus HYSTRICURUS Raymond Hysrricurus conicus (Billings) Plate XXNIII, Figs. 10-12 Bathyurus conicus Billings, 1859, Canadian Nat. and Geol., vol. iv, p. 266, text fig. 12d. Bathyurus conicus Whitfield, 1889, Bull. Amer. Mus. Nat. Hist., vol. ii, p. 61, ‘pl. xiii, figs. 15-21. Hystricurus conicus Raymond, 1913, Bull. Victoria Memorial Mus., 1, p. 60, pl. vii, fig. 9. Description.—Glabella conical, rounded at the anterior and almost straight across the occipital border ; no trace of glabellar furrows; surface marked by larger pustules, slightly more than their own diameter apart. Pygidium semicircular with the anterior margin not as sharply curved as the posterior, which is bordered by a narrow, flattened rim. Surface strongly trilobate, with the axial lobe extending to the posterior margin where it is obtusely pointed. Axial lobe marked by five transverse, short, sharply elevated rings, each of which is marked by a central spine-like tubercle, and one or two lateral nodes. Lateral lobes with four rings having two to four nodes on each. The Maryland specimens referred to this species consist of pygidia having the same general outline and the sharply elevated rings orna- mented with prominent nodes. The species has hitherto been found in the Beekmantown limestone of Canada, Vermont and New York. Occurrence—BEEKMANTOWN LIMESTONE (Cryptozoon steeli zone). Vicinity of Williamsport and Hagerstown, Maryland. Collection.—U. 8. National Museum. Family BATHYURIDAE Walcott Genus GONIURUS Raymond GonIuRUS cAuDATUS (Billings) Plate XXXVI, Fig. 14 Bathyurus caudatus Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 261, fig. 245. Goniurus caudatus Raymond, 1913, Bull. Victoria Memorial Mus., vol. i, p. 66. MARYLAND GEOLOGICAL SURVEY 341 Description.—Pygidium quite convex, with a strong triangular spine behind. Axis conical ; occupying less than one-third of the width, strongly » convex and clearly outlined by the dorsal furrow; apex of axis rounded and with four or five rings. Side lobes, with four or five broad and short ribs, which extend about half way to the margin. A smooth, slightly con- vex border all around extends backward, and forms the terminal spine. The well-marked triangular terminal spine of this species causes its identification to be extremely easy. So far only the pygidium of the species has been discovered. Occurrence.—BEEKMANTOWN LIMESTONE (Ceratopea zone). Vicinity of Halfway, Maryland. The types are from the Canadian rocks of New- foundland. Collection.—U. S. National Museum. Family OLENIDAE Genus TRIARTHRUS Green TRIARTHRUS FISCHER! Billings Plate LI, Fig. 16 Triarthrus fischeri Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 291, text fig. 280. Description—A. small cephalon of Triarthrus found in the Sinuites bed at Chambersburg, Pennsylvania, is so similar to Billings’ illustration of T. fischeri copied on pl. LI that it is believed to represent the same species in spite of the supposed difference in their geological horizons. It is possible that the strata in which the type of T. fischeri occurred are younger than now believed, and again it would not be surprising if this species, like many others, is repeated at several horizons in the geologic column. Triarthrus fischeri differs conspicuously from T. becki in the absence of tubercles along the median line of the axis. The types are from the Chazyan of Newfoundland. Occurrence—MarkTINSBURG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Collection. U. 8. National Museum. 342 SYSTEMATIC PALEONTOLOGY TRIARTHRUS BECKI Green Plate LI, Figs. 17, 18; Plate LII, Figs. 18-20; Plate LVI, Figs. 7-13 Triarthrus becki Green, 1832, Monograph Trilobites North America, p. 87, cast 34, pl. i, fig. 6. Calymene becki Hall, 1847, Pal. New York, vol. i, pp. 237, 250, pl. Ixvi, figs. 2a-k. Description.—* General form an elongated ellipse, with the posterior extremity narrower, and the sides often straight ; buckler broadly semioval, the posterior angles rounded; glabella of equal width from base to front, rounded before, deeply trilobate on each side, with a prominent thoracic ring at the base; frontal lobe narrowed longitudinally; thorax with 13 segments, those of the central lobe with a short spine or tubercle upon the back, those of the lateral lobes deeply grooved along the center; caudal shield with six or seven segments in the middle lobe, and five in the lateral lobes ; posterior extremity obtuse.”—Hall, 1847. Specimens of Triarthrus occur at several horizons in the Martinsburg shale of Maryland, and although their preservation is not always good, all seem to have the tubercle on the center of each axial segment, character- istic of the well-known and widely distributed 7. becki Green. Occurrence—MartinspurG SHALE. Chambersburg, Pennsylvania (Sinuites bed). Williamsport, Maryland (Corynoides bed). Fort Loudon, Pennsylvania, and Rickard Mountain, Maryland (Eden division). Collections.—Maryland Geological Survey, U. 8. National Museum. Family ASAPHIDAE Genus ISOTELUS DeKay IsOTELUS STEGOPS Green : Plate LVI, Figs. 3, 4 Isotelus stegops Green, 1832, Monograph Trilobites North Amer., p. 71, cast 26, 27. Description.—The species of Isotelus occurring in the Eden shale of the Ohio Valley hitherto referred to Isotelus gigas DeKay seems to represent a distinct species for which the name Isotelus stegops Green is here MARYLAND GEOLOGICAL SURVEY 3438 adopted. According to the researches of E. O. Ulrich as yet unpublished, Green’s casts of Isotelus stegops, the originals of which came from New- port, Kentucky, show no good differences from the Eden shale species of that region. Compared with Isotelus mazimus Locke, which I. stegops most closely resembles, the Eden form has the eye further forward, smaller spines, and the flattened border, especially of the pygidium, less distinct. Occurrence —MartTINsBURG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, and other localities iv Pennsylvania. Collection.—U. 8. National Museum. IsotELUS MEGISTOS Locke Plate LVIII, Figs. 10, 11 Isotelus megistos Locke, 1842, Amer. Jour. Sci., vol. xlii, p. 366, pl. iii, fig. 9. Asaphus (Isotelus) megistos Meek, 1873, Geol. Surv. Ohio, Pal., vol. i, p. 159, pl. xiv, fig. 13. Description.—Under this name and .also those of Isotelus maximus Locke and J. gigas DeKay, a number of distinct species ranging through the Mohawkian and Cincinnatian have undoubtedly been confused, with the result that these names have little stratigraphic significance. The discrimination of these species has been undertaken by E. O. Ulrich, whose work upon them is still in manuscript form. He has determined -that the fragments found in the Fairview deposits of Maryland and Pennsylvania are identical specifically with the types of Locke’s Isotelus megistos and also with the specimen illustrated later by Meek as Asaphus (Isotelus) megistos. Formerly the separation of these species was based upon the presence or absence of the genal spine, but it is now known that each species contains spinuous and aspinous forms, the difference between the two being presumably that of sex. The aspinous (? female) forms of these several species are quite difficult to distinguish from each other, but the spinous examples show good characters of differentiation. Thus, in the case of I. maximus and I. megistos, long considered synonymous, the free 344 SYSTEMATIC PALEONTOLOGY cheeks of each are different. In I. megistos the base of the spine is much wider and it tapers much more rapidly. The hypostoma furnishes further differences, for in I. megistos it shows coarser venations, the inner edges of the limb are straighter, and the whole hypostoma is relatively longer. Occurrence-—ManrtINsBurG SHALE (Fairview division, Orthorhyn- chula bed). Pennsylvania to Tennessee. Collection.—U.:S. National Museum. IsoTELus eigas DeKay Plate XLVIII, Figs. 23-25 Isotelus gigas DeKay, 1824, Annals Lyceum Nat. Hist. New York, vol. i, p. 176, pl. xii, fig. 1. Isotelus gigas Hall, 1847, Pal. New York, vol. i, p. 231, pl. 1x-Ixiii. Isotelus gigas Weller, 1903, Pal. New Jersey, vol. iii, p. 192, pl. xiv, figs. 6, 7. Isotelus gigas Raymond, 1914, Bull. Mus. Comp. Zool., vol. lviii, p. 248, pl. i, figs. 1, 2, pl. ii, figs. 2-5; pl. iii, fig. 3. Description.—* Outline of an entire individual subelliptical, with the anterior and posterior extremities somewhat pointed; the trilobation nearly obsolete. Head subtriangular to semi-elliptical in outline, convex, slightly flattened in front; the anterior margin rather sharply rounded; facial sutures meeting at an angle, at or just behind the frontal margin, from this point they describe a broad, subarcuate curve, and after passing around the eyes, they curve outward and then downward, intersecting the posterior margin at some distance outside of the eyes; glabella obscurely defined and more obscurely lobed; occipital furrow and seg- ment obsolete; free cheeks marked by an intramarginal furrow, above which their general surface is elevated into a more or less conspicuous node, crowned by the eye. Thorax with a broad axial lobe, occupying more than one-third the width, consisting of eight segments. Pygidium subtriangular in outline of nearly the same size and shape as the head, its lobation very obscure, especially in the larger individuals, the dorsal furrows being hardly distinguishable ; axis much narrower at its anterior extremity than the axis. of the thorax, tapering rapidly to the obtusely rounded posterior extremity, which lies at about one-fourth the length of MARYLAND GEOLOGICAL SURVEY 345 the pygidium from the posterior margin; plurae convex, smooth in the larger individuals, but in younger ones marked by about ten obscure segments, which also continue across the axis; the entire margin of the pygidium, except where it joins the thorax, bordered by a rather broad, slightly depressed, marginal border; the anterior, lateral angles bent abruptly downward.”—Weller, 1903. This frequently quoted trilobite has been often described and illustrated with the result that several species have undoubtedly been confused under the name. The specimens from the Cumberland Valley are fragmentary, although they agree so far as they go with the above description. The complete examples figured are from the type area of the species in New York. Occurrence.—CHAMBERSBURG LimEsTONE (Christiania bed). Penn- sylvania, Maryland, and Virginia. Collections.—Maryland Geological Survey, U. 8S. National Museum. TSOTELUS sp. Plate XX XVII, Fig. 9 Description —A single imperfect free cheek of Isotelus has been found in the Frederick limestone and is figured in the present report. It is of little value in determining the age of this limestone, as species of this general type have a long geologic range. Occurrence.—FREDERICK LimEstonE. Just east of Frederick, Mary- land. Collection —U. S. National Museum. Genus ASAPHELLUS Callaway ASAPHELLUS GYRACANTHUS Raymond Plate XXXII, Figs. 8-10 Asaphus canalis ? Cleland, 1900 (not Conrad), Bull. Amer. Pal., vol. iii, p. 128, pl. xvi, figs. 7, 8. Isotelus canalis Weller, 1902, Pal. New Jersey, vol. iii, p. 132, pl. v, figs. 5, 6. Asaphellus gyracanthus Raymond, 1910, Ann. Carnegie Mus., vol. vii, No. 1. p. 39, pl. xiv, figs. 5-7. 346 SYSTEMATIC PALEONTOLOGY Description.—Entire cephalon unknown. Free cheek broad, flat, tri- angular in outline, bearing a long spine at the genal angle. Glabella flat with a narrow depressed border in front and scarcely any traces of dorsal furrows. Eyes prominent with their longest diameter 5 mm. and between them a minute pustule. The pygidium is uniformly convex with a narrow, depressed border, and is semicircular in outline. Its axial lobe is narrow and improminent, with traces of three or four rings at the anterior end. Size of the pygidium varies from 10 mm. in width and 7 mm. in length to 50 mm. by 40 mm. Hypostoma quadrangular. This species much resembles Hemigyraspis collieana Raymond with fragments of which it is associated in Maryland, but its cephalon is longer and narrower and the axial lobe of the pygidium not so prominent. Occurrence.—BEEKMANTOWN LimESTONE (Stonehenge member). Vicinity of Hagerstown, Maryland. Tribes Hill limestone of New York and upper part of Kittatinny limestone of New Jersey. Collection—U. 8S. National Museum. Genus HEMIGYRASPIS Raymond HEMIGYRASPIS COLLIEANA Raymond Plate XX NIT, Figs. 11-15 _Asaphus marginalis Collie (not Hall), 1903, Bull. Geol. Soc. Amer., vol. xiv, H Ge collieana Raymond, 1910, Ann. Carnegie Mus., vol. vii, p. 41, pl. xiv, figs. 9-13. Description.—< Cephalon short and wide, glabella smooth, not out- lined, no glabellar furrows. Neck-furrow shallow, hardly visible. Eyes nearly halfway to the front of the cephalon, large, very far apart. Between the eyes is-a small median tubercle. Free cheeks short, wide, with long narrow spines at the genal angles. The anterior limb of the facial suture meets the frontal margin in front of the eye. There is a narrow depressed border on the front of the cranidium. “ Axial lobe of thorax one-third the total width; pleura grooved. Pygidium short, wide, semicircular in outline. Axial lobe narrow, rather prominent, showing traces of two or three rings. Pleural lobes convex, MaryLanp GEOLOGICAL SURVEY : 347 without traces of ribs. Border narrow, concave; doublure narrow, con- vex. Hypostoma quadrangular, widest in front, central portion convex, with a furrow and narrow border around the sides and posterior end. Surface of all parts, including the hypostoma, covered with imbricating striae. “One pygidium is 9.5 mm. long and 18 mm. wide; a larger one is 14 mm. long and 28 mm. wide.”—Raymond, 1910. As noted by Raymond this species much resembles Asaphus gyracanthus, but its cephalon is shorter and wider, the eyes are farther apart and the axial lobe of the pygidium is much more prominent. Occurrence—BEEKMANTOWN LIMESTONE (Stonehenge member). Hagerstown, Maryland and Bellefonte, Pennsylvania. Collection—U. 8. National Museum. Genus SYMPHYSURUS Goldfuss SYMPHYSURUS CONVEXUS (Cleland) Plate XXXII, Figs. 16-18 Asaphus convexus ? Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 128 (256), pl. xvi, fig. 4. Bathyurus sp. Cleland, 1900, Idem., pl. xvi, fig. 9. Illaenurus columbiana Weller, 1903, Pal. New Jersey, vol. iii, p. 133, pl. v, figs. 1-4. ‘ Bathyurus ? levis Cleland, 1903, Bull. Amer. Pal., vol. iv, p. 36, pl. ii, figs. 1, 2. Symphysurus converus Raymond, 1910, Ann. Carnegie Mus., vol. vii, No. 1, p. 42, pl. xiv, figs. 14-16. Description.—Entire cephalon unknown; glabella oblong, convex, with the eyes located halfway between the front and back. A small median tubercle present, below the eyes. Thorax unknown, but its axial lobe is probably narrow. Pygidium semicircular with a distinct axial lobe. Several indistinct annulations are present. The types of both this species and its synonym Bathyurus ? levis Cleland were obtained in the Tribes Hill limestone at Fort Hunter, New York. The species was identified by Weller in the Canadian portion of the Kittatinny limestone at Columbia, New Jersey, and under the belief that the species belonged to I/laenurus, the new name Illaenwrus colum- biana was proposed, the name I/laenurus convexus being preoccupied. 348 SYSTEMATIC PALEONTOLOGY Occurrence.—BEEKMANTOWN LIMESTONE (Stonehenge member). Hagerstown and Funkstown, Maryland. Collection.—U. 8. National Museum. Genus ONCGHOMETOPUS Schmidt ONCHOMETOPUS SIMPLEX Raymond and Narraway Plate XLVII, Fig. 18 Onchometopus simplex Raymond and Narraway, 1910, Ann. Carnegie Mus., vol. vii, p. 51, pl. xvi, figs. 6-8. Description. Cranidium moderately convex, slightly incurved at the front. Glabella flat, obscurely defined, expanding in front of the eyes and extending to the anterior margin; glabellar furrows absent, dorsal furrows present back of the eyes, very shallow. Neck-furrow absent. Eyes of medium size, situated a trifle more than their own length in front of the posterior margin. Behind the eyes there is a small median tubercle on the glabella. Free cheeks rounded at the genal angles. “ Thorax of eight flat segments. Axial lobe a little more than one-third the total width. Pleura with shallow grooves. “ Pygidium rounded in outline, three-fifths as long as wide. Axial lobe obscurely defined, the posterior end usually a little more prominent than the other portions. There are no annulations. The surface is uni- formly convex, without concave border. “ This species is similar to Onchometopus obtusus (Hall) of the Chazy, but the shell lacks the very coarse punctae of that form, and there are fewer traces of glabellar furrows. It differs from Onchometopus susae (Whitfield) in having a longer pygidium with a narrower and more distinct axial lobe. “ Onchometopus may be readily distinguished from Isotelus by the presence of a median tubercle onthe glabella, the absence of a concave border on both cephalon and pygidium, and by the somewhat narrower axial lobe in the thorax.”—Raymond and Narraway, 1910. The interesting Maryland trilobite referred:to the above-.species differs from all other Chambersburg forms in the absence of the.concave border MarRYLAND GEOLOGICAL SURVEY 349 on both the cephalon and pygidium. Although imperfect it agrees fairly. well in outline with the types of Onchometopus simplex. Occurrence.—CHAMBERSBURG LimESTONE (Nidulites bed). Wilson, Maryland. Black River limestone of Minnesota and Pennsylvania. Collection—U. 8. National Museum. Family ILLAENIDAE Genus ILLAENUS Dalman ILLAENUS AMERICANUS Billings Plate LI, Figs. 26-29 Illaenus americanus Billings, 1859, Canadian Nat. Geol., vol. iv, p. 371. Illaenus americanus Billings, 1865, Pal. Fossils, vol. i, Geol. Surv. Canada, p. 329, figs. 316a-d, 318. Illaenus americanus Raymond and Narraway, 1908, Ann. Carnegie Mus., vol. iv, Nos. 3, 4, pl. 1x, figs. 1-3. Description.—* Oblong, distinctly tri-lobed ; length two or three inches ; width from three-fifths to five-sixths the length: “ Head large, strongly convex, its height usually a little greater than its length measured on a straight line, sometimes abruptly bent down at less than half the length from behind, often uniformly arched from the front to the posterior margin, equal to about one-fourth of a sphere; length from front to posterior margin about two-thirds the width between the cheek angles in a straight line. The glabella is moderately convex; the dorsal furrows extend from one-fourth to a little more than one-third the whole length of the head, measured on the curve, and have an obscure sigmoid curve, at first outwards and then inwards, their anterior ex- tremities usually turning a little outwards; they are distant from each other not quite one-half the whole width of the head. The eyes are of moderate size, about two lines in length, about half their length from the posterior margin, and half the width of the glabella from the dorsal furrows. The cheek angles are rounded, and the posterior margin of the head makes with the lateral lower margin, as seen in a side view usually a right angle, but in some specimens an obtuse angle of nearly 100°, owing to the variable extent to which the front part of the head is produced 350 SYSTEMATIC PALEONTOLOGY downwards. In some the portion of the posterior margin outside of the eye curves forwards, and brings the cheek angle to a position in front of the eye. In others, it is behind the eye. The space between the eye and the dorsal furrows is convex, and the eye itself seems to be rather strongly protuberant or subconical. The movable cheek is subtriangular, its width at the posterior margin about one and a half the distance of the eye from the dorsal furrow, its length along the lower margin a little greater than its posterior width. The anterior margin of the whole head is uniformly rounded, with the exception of a slight concave curve just outside of the suture. In some specimens in which the front part of the head is most abruptly bent down the middle portion of the front margin is depressed convex or nearly straight. “Thorax with ten segments. Axis moderately convex, from a little more than one-third to nearly one-half the width of the whole animal, a little wider at the anterior than at the posterior segment; the sides some- times straight, and sometimes slightly eurved outwards. On each side of the axis there is a flat space between the side of the axis and the bend of the pleurae. The width of this space is between one-third and one-half the width of the axis. The pleurae are bent at the fulcra at an angle ~ which varies in different individuals, from 25° to 45°, and at nearly one-half their length from the side of the axis. “Pycidium usually a little shorter than the thorax; varying from moderately to rather strongly convex; the posterior margin broadly and uniformly rounded; the anterior angles truncated nearly half the whole length of the pygidium ; the straight sides formed by the truncation form- ing an angle of from 40° to 60° with the longitudinal axis of the body. The axis of the pygidium is well defined at the anterior margin by the dorsal furrows, which die out at about one-third or one-half the length, converging towards each other, and sometimes obscurely defining the apex.”—Billings, 1865. Occurrence—MartinsBurc SHALE (Sinuites bed). Chambersburg, Pennsylvania. Trenton limestone of Ottawa, Canada, and many other localities. Collection.—U. S. National Museum. MARYLAND GEOLOGICAL SURVEY 351 Genus BUMASTUS Murchison BUMASTUS TRENTONENSIS Emmons Plate LI, Figs. 30-33 Bumastus trentonensis Emmons, 1842, Nat. Hist. New York, Geol., vol. ii, p. 390, fig. 1. Bumastus trentonensis (part) Clarke, 1897, Geol. Minnesota, vol. iii, pt. 2, . 718, Bona milleri Raymond and Narraway, 1908, Ann. Carnegie Mus., vol. iv, p. 249, pl. 1xi, figs. 9, 10, pl. Lxii, figs. 3-5. Description.—Emmons’ figure of his type specimen of Bumastus tren- tonensis represents an example with eight segments to the thorax. Before this specimen could be restudied it was lost and the validity of the name has been questioned. It is unnecessary to enter into a history of the synonymy of this species, as this was fully discussed in 1908 by Raymond and Narraway. However, a species of Bumastus with eight segments occurs in the Trenton limestone of New York which, according to the present arrangement of species of the genus, has no name. This species agrees with Emmons’ figure fairly well and it seems reasonable to retain his name of Bumastus trentonensis. Occurrence—MArtTINsBURG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Trenton limestone of New York. Collection.—U. 8. National Museum. Family DIKELOCEPHALIDAE Genus SAUKIA Walcott SAUKIA STOSEI Walcott Plate XXVII, Figs. 6-8 Saukia stosei Walcott, 1914, Smithsonian Misc. Coll., vol. lvii, No. 13, p. 384, pl. Ixix, figs. 3-5; pl. Ixx, figs. 12, 12a. Description.—“ This species belongs to the S. pepinensis form of Saukia, and is most nearly related to Saukia fallax, but it has a propor- tionately larger palpebral lobe. The associated pygidium differs from the pygidium found with 8. fallax in Texas in having a longer axial lobe,. and the surface is strongly granulated instead of being smooth as in S. fallax.”’—Walcott. 23 352 SYSTEMATIC PALEONTOLOGY Occurrence.—ConococHEaaus Limestone. Near Scotland, Franklin County, Pennsylvania. Near Funkstown, Maryland. Collections.—Maryland Geological Survey, U. 8. National Museum. Family PROETIDAE Genus PROETUS Steininger PROETUS LATIMARGINATUS Weller Plate LI, Figs. 21-25 Proetus latimarginatus Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 195, pl. xiv, figs. 17-24 (? 25). Description.—“ Head sublunate in outline, the genal angles produced into long, sharp spines. Glabella elevated, broadly subconical, rounded in front; lateral furrows nearly obsolete exteriorly, but sometimes their position is indicated by dark lines on the surface, which seem to indicate an internal thickening of the test; the two anterior pairs are short and lie in front of the eye-lobes ; they are close together, and are directed obliquely backward from the margin of the glabella; the posterior pairs are more conspicuous than the others, and are sometimes marked by slight depres- sions ; they are situated a little in front of the middle of the eye-lobes, and are directed obliquely backward from the margin of the glabella, becoming more curved posteriorly, joining the occipital furrow at nearly right angles. The dorsal furrow well defined throughout. Occipital furrow sharply impressed, deeper than the dorsal furrow. Occipital segment with subparallel margins, scarcely as highly elevated as the glabella, marked by a small, rounded tubercle at its central point. Palpebral lobes of moderate width, sub-semicircular in outline, depressed below the level of the glabella. Facial sutures curving into the margin of the glabella, both in front and behind the palpebral lobes; posteriorly they intersect the margin of the head close to the axial lobe; in front of the palpebral lobes they curve outward nearly to the margin of the head, where they make a rather sharp bend and recurve inwardly, intersecting the anterior margin at some distance from its median point. Anterior limb of the cranidium broad, with a convex marginal border, between which and the MarYLAND GEOLOGICAL SURVEY 353 glabella there is a rather broad, shallow, concave furrow. Free cheeks. depressed-convex, with the eyes abruptly elevated, marked by a rather broad marginal border on both the lateral and posterior margins, on the inner side of which there is a rather sharply impressed furrow. Pygidium small, sub-semicircular in outline; the posterior margin regularly rounded ; the anterior margin straight nearly to the lateral angles, where it is curved backward. Axis narrow, not reaching to the posterior margin, marked by six or seven annulations. Pleurae convex, much depressed below the axis, marked by five or six grooved segments, only the anterior two or three of which reach the margin of the pygidium. Thorax un- known. The entire surface of well-preserved specimens is finely granu- lose.”—Weller, 1903. The specimens from the basal Martinsburg shale are not as complete as the types upon which the above description was based, but there seems little doubt of their specific identity. Occurrence.—MAaRTINSBURG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Trenton limestone of New Jersey. Collection.—U. S. National Museum. Genus CYPHASPIS Burmeister CYPHASPIS MATUTINA Ruedemann Plate LI, Figs. 12-14 Cyphaspis matutina Ruedemann, 1901, New York State Mus. Bull., No. 49, p. 62, pl. iv, figs. 5-7. Description.—* The glabella is short, roundish, subquadrangular, moderately and uniformly convex, sloping equally to all sides; surrounded by deep dorsal furrows and an equally deep frontal furrow. Three pairs: of glabellar furrows are discernible, the first two faint, short and oblique, the third semicircular, extending to the occipital furrow, and separating a pair of less convex lobes, which extend a little beyond the lateral margin of the first and second lobes; the broad border slopes steeply to a narrow tim, somewhat upturned at the margin. The glabella and rim are apparently completely smooth, but show under the glass fine transverse 354 SYSTEMATIC PALEONTOLOGY striae. Neck ring nearly flat, depressed, with a central tubercle; occipital furrow distinct, nearly straight. Sutures begin at the anterolateral angles of the margin, extend in the direction of the second glabellar lobe to near the glabella, and then curve backward.”—Ruedemann, 1901. This species was based upon two small cranidia, both of which are illustrated in the present report. The material here identified with C. matutina consists of imperfect cranidia only, so that nothing further can be added to the specific description. Occurrence-—MarTINSBURG SHALE (Sinuites bed). Chambersburg, Pennsylvania. Rysedorph conglomerate at base of Trenton, Rensselaer County, New York. Collection.—U. S. National Museum. Family LICHADIDAE Genus AMPHILICHAS Raymond AMPHILICHAS TRENTONENSIS (Conrad) Plate LI, Figs. 8-10 Asaphus ? Trentonensis Conrad, 1842, Jour. Acad. Nat. Sci. Philadelphia, vol. viii, p. 277, pl. xvi, fig. 16. Platynotus trentonensis Hall, 1847, Pal. New York, vol. i, p. 235, pl. Ixiv, figs. la-d. Platymetopus trentonensis Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 200, pl. xv, figs. 17-19. Description.— Head ventricose, the curve along the median line from the posterior to the anterior margins being very nearly a semicircle, . sub-semicircular in outline, attaining a breadth of 35 or 40 mm. The glabella very large, occupying nearly the entire breadth of the cranidium, strongly protuberant in front; with a single pair of glabellar furrows, which originate at the anterior, lateral margins, and, after curving inward, then backward and then slightly outward again, forming some- thing more than a semicircle, they join the occipital furrow, dividing the glabella into three lobes; the frontal or median lobe is broad in front, becoming narrower posteriorly to a point back of the middle of the head, MaryLanp GEOLOGICAL SURVEY 355 and then again broadens out, becoming nearly as wide on the occipital furrow as it was on the anterior margin; the two lateral lobes about as prominent as the median lobe, subcrescentiform in outline. Dorsal fur- rows concave inward, about as deeply impressed as the glabellar furrows. Fixed cheeks rather broad along the posterior margin of the head, becom- ing rapidly narrower to a point just behind the palpebral lobe ; the palpe- bral lobe rather prominent, the cheek becoming very narrow anteriorly. Occipital furrow and occipital segment well defined, extending across the fixed cheeks. The entire surface ornamented with small, low, rounded tubercles, somewhat variable in size. Free cheeks, thorax and pygidium unknown.”—Weller, 1903. The above description by Weller is the most detailed that has so far been published, and as the specimens now under study show no additional features both his description and figures are reproduced. Occurrence.—MartTinsBura SHALE (Sinuites bed). Carlisle and Chambersburg, Pennsylvania, and Strasburg, Virginia. Collection.—U. S. National Museum. Family ODONTOPLEURIDAE Genus ACIDASPIS Murchison ACIDASPIS ULRICHI n. sp. Plate XXXVI, Figs. 6-8 Description.—The most interesting species in the fauna of the Fred- erick limestone is a remarkably spinose trilobite represented by rather numerous fragments of the free cheek with its extended genal spine. Unlike most American species of Acidaspis and allied genera, the. spines on the free cheek of the present one continue to the end of the genal spine. These spines are regularly and closely placed and are of consider- able length along the free cheek. They decrease in length along the genal spine, but they are still conspicuous at its end. Another unusual feature is a great curvature of the free cheek with its genal spine, apparently indicating that the latter were directed over the thorax of the trilobite. 356 SYSTEMATIC PALEONTOLOGY The general aspect of this ‘trilobite is not unlike certain Huropean species of Acidaspis. This species can be recognized easily from its free cheeks, but more of the trilobite is necessary before its affinities can be definitely determined. The specific name is in honor of Dr. E. O. Ulrich in appreciation of his work on the faunas and stratigraphy of the Appalachian Valley. Occurrence.—FREDERICK LimEsToNE. Frederick, Maryland. : Collections.—Maryland Geological Survey, U. 8. National Museum. Order PROPARIA Family CALYMENIDAE Genus CALYMENE Brongniart CALYMENE GRANULOSA (Foerste) Plate LVI, Figs. 1, 2 Calymene callicephala granulosa Foerste, 1909, Bull. Sci. Lab. Denison Univ., vol. xiv, p. 294. Description.—This species is one of several that have usually been identified as Calymene callicephala, but the latter name has been dropped on account of uncertainty as to the species represented. The Eden form of Calymene differs conspicuously from other Cincinnatian species of the genus in the presence of numerous granules upon the carapace. Other differences, such as smaller size and a less strongly elevated anterior border of the cephalon, may be noted, but the granulose surface is the best marked feature. Occurrence.-—MartinsBurRG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania; Cowans Gap, five miles northeast of McConnellsburg; and Tuscarora Mountain, two and one-half miles southeast of McConnellsburg, Pennsylvania; ‘Rickard Mountain, Washington County, Maryland. Eden shale at Cin- cinnati, Ohio. Collections.—Maryland Geological Survey, U. S. National Museum. MaryYLAND GEOLOGICAL SURVEY 3857 CALYMENE SENARIA Conrad Plate LI, Fig. 15 Calymene senaria Conrad, 1841, 5th Ann. Rept. Geol. Surv. New York, pp. 38, 49. Calymene senaria Hall, 1847, Pal. New York, vol. i, p. 238, pl. 64, figs. 3a-n. Calymene senaria Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 203, pl. xv, fig. 23. Description.—* Head sub-semicircular or sublunate in outline, the anterior and lateral margins being more or less nearly regularly rounded, and the posterior broadly sinuous, with the posterior lateral extremities bluntly subangular or abruptly rounded. Free cheeks irregularly tri- angular in outline, with thick, rounded, lateral margins, defined by a distinct, rounded marginal furrow, which is continuous with the furrow separating the anterior end of the glabella from the prominent, elevated, anterior margin of the head. Facial sutures originating just in front of the genal angles, passing obliquely forward and inward for a little more than half the distance to the eyes, then curving inward to the base of the eye-lobe, and after passing around the eyes, extending forward and intersecting the anterior margin at points a little nearer together than the breadth between the eyes. Eyes small and rather prominent. Glabella more prominent than the cheeks and separated from them by deep, dorsal fur- tows, about as wide behind as its length, including the occipital segment, much narrower in front; the frontal and three pairs of lateral glabellar lobes separated by three pairs of glabellar furrows, of which the anterior pair is much the faintest and shortest; each member of the second pair extends about one-fourth the distance across the glabella, slightly curved posteriorly, the posterior pair deeper and wider than either of the others, each member extending about one-third the distance across the glabella and directed obliquely backward. Occipital furrow deep and prominent, connecting with the dorsal furrows and less conspicuously with the mar- ginal furrows of the posterior margin of the fixed cheeks, arching slightly forward at the middle of the glabella. Occipital segment well defined, arching a little forward, about as high as the most prominent portion of the glabella in front. Fixed cheeks convex, provided with a deep, broad furrow along their posterior margin. 3858 SYSTEMATIC PALEONTOLOGY “ Pygidium wider than long, more or less subtrigonal in outline, but with the anterior margin broadly rounded. Axis well defined, convex, extending nearly to the posterior margin, with five or six transverse seg- ments, which grow fainter posteriorly. The pleurae convex, each with about five segments, which are furrowed distally. Whole surface of the test minutely granular.”—Weller, 1903. The fragments of this species noted in the basal part of the Martins- burg shale agree in all characters with the New Jersey Trenton specimens described in detail by Weller as above. Occurrence—MantINspurG SHALE (Sinuites bed). Chambersburg, Pennsylvania, and Strasburg, Virginia. Collections.—Maryland Geological Survey, U. 8. National Museum. Family CHEIRURIDAE Genus CERAURUS Green CERAURUS PLEUREXANTHEMUS Green Plate XLITI, Figs. 22, 23 Ceraurus pleureranthemus Green, 1832, Monthly Amer. Jour. Geol., vol. i, p. 560, pl. iv, fig. 10. Ceraurus pleurexanthemus Green, 1832, Mono. Trilobites North America, p. 84, text fig. 10, cast 33. Ceraurus pleurezanthemus Hall, 1847, Pal. New York, vol. i, p. 242, pl. Ixv, figs. la-c, le-g. Ceraurus pleurexanthemus Weller, 1903, Geol. Surv. New Jersey, Pal., vol. iii, p. 204, pl. xv, fig. 28. Ceraurus pleurexranthemus Raymond and Benton, 1913, Bull. Mus. Comp. Zool., vol. liv, p. 528, pl. i, fig. 1; pl. ii, figs. 1, 2, 7. Description Head crescentiform in outline, with the posterior lateral angles extended into long, curved, genal spines, which.are attached to the fixed cheeks. Free cheeks irregularly triangular in outline, the eyes small. Facial suture starting at the lateral margin, and after extending inward toward the glabella, making a sharp turn forward just back of the eye, and after passing around the eye, curving gently for- ward, cutting the anterior margin of the head in front of the glabella. Glabella prominent, convex, broadest in front, extending nearly to the MarYLAND GEOLOGICAL SURVEY 359 anterior margin of the head. Glabellar furrows well defined, but not extending across the glabella. The two anterior pairs straight, each portion extending over about one-fourth the width of the glabella. The third pair extending inward about as far as the other two, and then bending abruptly backward and joining the occipital furrow, leaving the posterior glabellar lobes more or less detached. Occipital furrow deep and well defined, arching a little forward upon the glabella extended laterally upon the fixed cheeks nearly to the lateral margins, where it joins a marginal furrow just in front of the genal spine, which passes anteriorly. Occipital segment well defined. Dorsal furrow rather sharply impressed. Fixed cheeks convex, their posterior lateral angles extended into prominent, curved, genal spines. Whole surface of the head, except the dorsal, glabellar, occipital and marginal furrows, strongly granulose or papillose, with some scattered tubercles larger than the others.”— Weller, 1903. The above description by Weller applies in detail to the characters of the head fragments found in the Chambersburg limestone. Several species have been confused under the name of Ceraurus pleurexanthemus and better material may show the Chambersburg limestone specimens to be incorrectly referred here. Occurrence—CHAMBERSBURG LIMESTONE (Caryocystites bed). Fort Loudon, Franklin County, Pennsylvania. Black River of New York, Canada, etc. Collections.—Maryland Geological Survey, U. 8. National Museum. Genus PLIOMEROPS Raymond PLIOMEROPS SALTERI (Billings) Plate XNAVI, Fig. 13 Amphion salteri Billings, 1861, Canadian Nat. and Geol., p. 322, text fig. 6. Amphion salteri Billings, 1865, Pal. Foss., vol. i, Geol. Surv. Canada, p. 352, text fig. 339. Description.—Pygidium small, about 6 mm. long and 10 mm. wide at the base. Glabella convex, oblong, one-third the width of the head, with 360 SYSTEMATIC PALEONTOLOGY straight sides and a narrow margin in front; neck furrow extending entirely across; three pairs of glabellar furrows directed slightly back- ward, their inner extremities separated by about one-third the width of the glabella. Fixed cheeks covered with small tubercles and separated from the glabella by a deep groove on each side. Pygidium 6 mm. long and about the same at its greatest width; front margin rounded and the posterior somewhat straight. Axis conical and strongly convex with five or six well-defined segments. Pleurae of the pygidium five on each side and nearly parallel with the axis in their posterior half, then curving inward to join the axial segments. Identified somewhat doubtfully in the Middle Beekmantown (Cera- topea zone) in the Appalachian Valley of Maryland and southern Penn- sylvania. Imperfect pygidia with the characteristic pleurae were observed in exposures along the Cumberland Valley Railroad northeast and south- east of Halfway, Maryland. Occurrence—BEEKMANTOWN LIMESTONE (Ceratopea zone). Halfway, Maryland. Collection.—U. S. National Museum. Family PHACOPIDAE Genus PTERYGOMETOPUS Schmidt PTERYGOMETOPUS CALLICEPHALUS (Hall) Plate XLITI, Figs. 18-21 Phacops callicephalus Hall, 1847, Pal. New York, vol. i, p. 247, pl. Ixv, figs. 3a-i. Pterygometopus callicephalus Clarke, 1894, Geol. Minnesota, vol. iii, pt. 2, p. 731, text figs. 51, 52; p. 732. Pterygometopus callicephalus Weller, 1908, Geol. Surv. New Jersey, Pal., vol. iii, p. 206, pl. xv, figs. 29-32. Description.—“ Head sublunate in outline, obtusely subangular in front, genal angles broad and rounded, with no indication of spinules. Glabella large, depressed-convex, broad and rounded in front, becoming much narrower behind; frontal lobe large, subelliptical in outline; MARYLAND GEOLOGICAL SURVEY 361 anterior pair of glabellar furrows starting from opposite the anterior extremities of the eyes, directed obliquely backward and each one extend- ing over a little more than one-third the width of the glabella; second pair of glabellar furrows shorter and a little shallower than the first, directed obliquely forward; third pair of glabellar furrows directed toward the axis of the glabella for a short distance and then bending abruptly back- ward and joining the occipital furrow, leaving the small, basal glabellar lobes wholly detached. Occipital furrow rather deep and broad. Occipital segment rather broad, its elevation about even with the glabella in front, its posterior margin convex. Palpebral lobes prominent, their elevation being nearly that of the glabella, separated from the glabella by the deep dorsal furrow, and marked by a conspicuous furrow just within the border of the eye. Eyes large, lunate, their inner margins elevated nearly or quite to the height of the glabella, their anterior ends opposite the first glabellar furrows and their posterior ends reaching nearly to the occipital furrow. Cheeks, outside the eyes, sloping rather abruptly to the lateral margins of the head ; marked along the posterior margins to a point about one-half the distance from the eye to the margin by the narrow, but rather sharply impressed, occipital furrow, whose distal extremity is rather abrupt; the lateral borders marked by an ill-defined marginal furrow, which originates at the outer extremity of occipital furrow, and after passing forward nearly parallel with the margin, joins the dorsal furrow just in front of the eye. “ Pygidium subtriangular in outline, rather abruptly rounded or sub- ‘angular posteriorly. Axis prominent, but rather narrow, its margin slightly incurved and abruptly rounded behind, marked by from eight to ten somewhat sinuous annulations ; the pleurae slightly flattened adjacent to the axis, but soon curving rather abruptly to the lateral margins, marked by about six grooved segments, with slight traces of others posteriorly. “ Surface of the glabella, palpebral lobes, occipital segment and cheeks inside the marginal furrow distinctly pustulose, the little tubercles being more or less irregular in size; upon the cheeks outside the border of the 362 SYSTEMATIC PALEONTOLOGY eyes the papillae are much less conspicuous than upon the glabella and the marginal border is perfectly smooth. Pygidium unornamented, except by the grooves marking the segments, which do not extend entirely to the border, thus leaving a plain, perfectly smooth, narrow marginal border.”—Weller, 1903. Occurrence.-—CHAMBERSBURG LIMESTONE (Tetradium cellulosum bed). Several localities south of Chambersburg, Pennsylvania. This species has hitherto been supposed to be restricted to the Trenton rocks of the United States and Canada. Collection.—U. S. National Museum. Subclass E UCRUSTACEA Superorder BRANCHIOPODA Order NOTOSTRACA Genus RIBEIRIA Sharpe RIBEIRIA ? NUCULITIFORMIs Cleland Plate XXXI, Figs. 18, 14 Ribeiria ? nuculitiformis Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 133 (261), pl. xvi, figs. 10-14. Description.—Shell small, varying from 1.5 mm. by 3 mm. to 6 mm. by 12 mm., compressed laterally, with the dorsal margin concave and the sides convex. In casts, a deep notch about one-fourth the length of the shell is shown just below the beak and extends obliquely towards the middle of the ventral side. The shell of this interesting crustacean much resembles a species of the pelecypod genus Nuculites, whence the specific name. Occurrence-—BEEKMANTOWN LimEsTONE (Stonehenge member). Hagerstown, Maryland. An extremely abundant fossil in the Tribes Hill limestone at Fort Hunter, New York. Collection.—U. 8. National Museum. MaryLanp GEOLOGICAL SURVEY 363 Superorder OSTRACODA Family LEPERDITIIDAE Genus ISOCHILI..A Jones IsOCHILINA GREGARIA (Whitfield) Plate XXXVI, Figs. 10-12 Primitia gregaria Whitfield, 1889, Bull. Amer. Mus. Nat. Hist., vol. ii, p. 58, pl. xiii, figs. 3-5. Isochilina gregaria Jones, 1890, Quart. Jour. Geol. Soc. London, vol. xlvi, p. 22, pl. i, figs. 9, 10. Lsochilina amiana Ulrich, 1891, Jour. Cincinnati Soc. Nat. Hist., vol. xiii, pt. 1, p. 180, pl. xi, figs. 12a-c. Isochilina ottawa var. intermedia Jones, 1891, Cont. Micro-Pal., Geol. Surv. Canada, pt. 3, p. 66, pl. x, figs. 10, 11. Description—Carapace about 4 mm. long, obliquely oval in form; hinge line straight, in length about three-fifths that of the valves. Sur- face of valves convex, most elevated across the narrow end. Sulcus poorly defined, broadly triangular extending from about the middle of the valve to the hinge. Surface of valves marked by numerous widely spaced pits. On each side of the sulcus there is usually a well-defined node or tubercle and often one is at its lower extremity. A species of similar size and shape and with the surface markings of the Vermont type specimens occurs in poor preservation, but sometimes in abundance on the weathered limestone surfaces of the Middle Beek- mantown of Pennsylvania and Maryland. Occurrence.—BEEKMANTOWN LIMESTONE (Ceratopea zone). Several of the outcrops along the National Highway west of Hagerstown and the turnpike to Williamsport, Maryland. Collections.—Maryland Geological Survey, U. 8. National Museum. IsoCHILINA SEEYLI (Whitfield) Plate XXXV, Fig. 12 Primitia seelyi Whitfield, 1889, Bull. Amer. Nat. Hist., vol. ii, p. 60, pl. xiii, figs. 6, 7. Isochilina seelyi Jones, 1890, Quart. Jour. Geol. Soc. London, vol. xlvi, p. 22, pl. i, fig. 7. 364 SYSTEMATIC PALEONTOLOGY Description.—Valves about 4 mm. in length, and not quite 3 mm. long, with the straight or dorsal margin a trifle more than three-fifths of the entire length. Valves convex, and wider at the posterior end; cardinal] angles distinct. Anterior and posterior ends with flattened margin, narrowing along the basal border and disappearing along the mid-ventral edge. Surface covered with moderately large, depressed pits, most of which have an elevated granule in the center. A nearly circular, smooth spot, and above it a rapidly widening area also without pits, extending to the dorsal border, replaces the usual sulcus or tubercles of the surface of such ostracoda. The surface punctae and the smooth spot in the anterodorsal part of the valve easily distinguish this species. The types were found in the Beekmantown limestone at Shoreham, Vermont. Occurrence —BEEKMANTOWN LIMESTONE (Turritoma zone). Huyett, Maryland. Collections.—Maryland Geological Survey, U. S. National Museum. Genus LEPERDITIA Rouault LEPERDITIA FABULITES (Conrad) Plate XX XIX, Fig. 16; Plate XLITI, Figs. 1-5 Cytherina fabulites Conrad, 1848, Proc. Acad. Nat. Sci. Philadelphia, vol. i, p. 332. Leperditia fabulites Ulrich, 1891, Jour. Cincinnati Soc. Nat. Hist., vol. xiii, p. 173, pl. xi, figs. la-d, 2. Leperditia fabulites Ulrich, 1894, Geol. Minnesota, vol. iii, pt. 2, p. 634, pl. xliii, figs. 1-14. Leperditia fabulites Weller, 1908, Geol. Surv. New Jersey, Pal., vol. iii, p. 208, pl. xiii, figs. 11, 12. Description.—* Carapace of medium size, obliquely subovate, compara- tively long, widest posteriorly; ventral curves moderate, strongest just behind the mid-length ; cardinal line straight, comparing with the length of the valve as two is to three, the two extremities almost equally angular; hight of ends about as three is to four, both obliquely truncate above, the anterior narrowly rounded in the middle; the posterior outline more MARYLAND GEOLOGICAL SURVEY 365 broadly and evenly curved though having the usual backward swing. Ventral edge of carapace obtuse, scarcely flattened, with a slight furrow on each side near the edge of the right valve in which a row of minute punctae is generally distinguishable; overlap extending all around the free edges, strongest ventrally ; except in rare instances, neither valve has a flange or flattened border, and when present it is in all cases very narrow and undefined ; dorsal edge somewhat thickened, especially upon the left side. Surface of the valves smooth or very faintly pitted, rather evenly convex with the greatest thickness somewhat beneath the center ; a low ridge-like thickening along the posterior half of the dorsal margin of the left valve is to be noticed. Eye tubercle just distinguishable in most cases, rarely so distinct as in the specimen figured, often not to be detected. On the inner surface, however, it is always marked by a dis- tinct pit. Muscle spot not distinguishable externally except when the specimens are weathered, but on the inner side it is often well marked and surrounded by fine reticulating radial lines, short dorsally, longest post-ventrally. On the inner side of the ventral edge of the right valve there are two rows of small papillae, three to five in each, the number seeming to increase with age. The purpose of these papillae, one series of which occurs in the anterior third, the other in the posterior evidently was to prevent undue overlapping of the valves by presenting an obstacle to the entering ventral edge of the left valve.”—Ulrich, 1894. Although this species has been cited as a wide-spread characteristic fossil of both the Stones River and Black River groups, the typical form is really restricted to the latter rocks. The original types were described from the Platteville limestone of Wisconsin, the equivalent of the Low- ville limestone of more eastern localities. Occurrence.—-CHAMBERSBURG LIMESTONE (Tetradium cellulosum bed). Fort Loudon and other localities in Franklin County, Pennsylvania. Stoners River Limestonr. Pinesburg and Wilson, Maryland. Collections —Maryland Geological Survey, U. S. National Museum. 366 SYSTEMATIC PALEONTOLOGY Genus LEPERDITELLA Ulrich LEPERDITELLA TUMIDA (Ulrich) Plate XLIII, Figs. 10-12 Leperditia tumida Ulrich, 1892, Amer. Geol., vol. x, p. 264, pl. ix, figs. 1-3. Leperditella tumida Ulrich, 1894, Geol. Minnesota, vol. iii, pt. 2, p. 636. Description.—Valves ovate, leperditoid, with a straight back, rather short, with the posterior end widest, tumid, the convexity of the surface, except for a slight flattening and lengthening of the dorsal and anterior slopes, nearly uniform. Surface obscurely punctate, otherwise smooth, there being no external signs of either the eye-tubercle or muscle spot. Right valve a little smaller than the left and fitting into a groove in it. Length of a large right valve, 2.6 mm.; height, 1.82 mm.; thickness, 0.75 mm. This is one of the characteristic microscopic fossils of the Lowville limestone in the Ohio and Appalachian valleys. Occurrence—CuamBerspurG Limestone (Tetradium cellulosum bed). Fort Loudon and other localities in Franklin County, Pennsyl- ‘vania. Collections.—Maryland Geological Survey, U. 8. National Museum. Genus APARCHITES Jones APARCHITES MINUTISSIMUS (Hall) Plate LV, Fig. 33 Leperditia (Isochilina) minutissima Hall, 1872, 24th Rep. New York State Cab. Nat. Hist., p. 231, pl. viii, fig. 13 (advance sheets, 1871, p. 7). Leperditia (Isochilina) minutissima Hall and Whitfield, 1875, Geol. Surv. Ohio, Pal., vol. ii, p. 102, pl. iv, fig. 4. Aparchites minutissimus Ulrich, 1889, Geol. Surv. Canada, Cont. Micro.-Pal., pt. 2, p. 49, pl. ix, fig. 5. Description.—“ Carapace minute, less than two-hundredths of an inch in length, the width being about two-thirds the length, greatest at the anterior third, giving a broadly ovate outline, with a straight cardinal margin of about two-thirds the length of the valve. MARYLAND GEOLOGICAL SURVEY 367 “Surface of the valves smooth, rising into an obtusely pointed promi- nence at the anterior third of the length; basal margins-of the valves not overlapping, so far as can be ascertained.”—Hall and Whitfield, 1875. This minute ostracod may be readily recognized by its Leperditia-like carapace with non-overlapping valves, the surface of which is smooth and rises into an obtuse prominence. An abundant fossil in the Cin- cinnatian rocks of the Ohio Valley, particularly in the Eden shale. Occurrence.—MARTINSBURG SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Fort Loudon, Pennsylvania, and debris on the west slope of Rickard Mountain, Washington County, Maryland. Collection.—U. 8. National Museum. Family BEYRICHIIDAE Genus DREPANELLA Ulrich DREPANELLA MACRA Ulrich Plate NLITI, Figs. 13-15 Drepanella macer Ulrich, 1894, Jour. Cincinnati Soc. Nat. Hist., vol. xiii, p. 119, pl. viii, figs. 4a-c. : Drepanella macra Ulrich and Bassler, 1908, Proc. U. S. Nat. Mus., vol. xxxv, p. 291, fig. 17, pl. xli, figs. 12-14. Description.—* Valves subquadrate, about 2.0 mm. long and 1.25 mm. high, with the body very thin and shallow, the thickness of the entire carapace at a point near the middle being only about 0.8 mm. Ventral margin straight or sinuate; ends subequal, the posterior a little the most curved ; postero and antero-dorsal regions angular, the angles 10 or 15 degrees greater than a right angle. Ventral edge slightly thickened. Marginal or sickle-shaped ridge high, projecting beyond the dorsal edge, running parallel with and very close to the abrupt posterior margin ; then curving more rapidly than does the outline of the valve into the ventral margin, it gradually increases its distance from the ventral edge, and in a slightly flexuous manner traverses the valve for almost its entire length, terminating at a point near the middle of the anterior margin. Postero-median ridge consisting of three prominently confluent nodes, the 24 368 SYSTEMATIC PALEONTOLOGY uppermost projecting considerably beyond the dorsal margin. Antero- median node large, prominent and of triangular form. Antero-dorsal node projecting prominently beyond the edge, but not as high, and only about half as large as the antero-median one.”—Ulrich, 1894. The types of this striking ostracod were found in the topmost division (Lebanon) of the Stones River limestone of Central Tennessee. Occurrence.—CHAMBERSBURG LimeEsToNE (Tetradium cellulosum bed). Fort Loudon, Pennsylvania. Collections.—Maryland Geological Survey, U. 8. National Museum. Genus MAGRONOTELLA Ulrich MacroNOrELLA ULRICHI Ruedemann Plate XLITI, Figs. 6-9 Macronotella ulrichi Ruedemann, 1901, New York State Mus. Bull., No. 49, p. 83, pl. vi, figs. 6-16; pl. vii, fig. 1. Description.—“ Valves three-fourths circular to subovate; dorsal out- line rarely straight, mostly prominent in the central part, specially in older specimens; cardinal angles obtusely rounded to shortly truncate ; posterior margin with a little longer truncation, lateral and ventral margins forming approximately a continuous circular line; in larger specimens the anterior and posterior margins more strongly rounded, and the ventral margin less curved; free edges in most specimens with’ a broad depressed border and beveled edge. Surface strongly convex, culminating in the dorsocentral region ; in some specimens almost smooth, with only faint, widely and irregularly distributed circular impressions ; others with very large deep pits; on the apex always a flat. smooth circular area. Walve projecting slightly above the straight cardinal line, and forming a broad, low, triangular, reentrant cardinal area. “ Dimensions: Length, 2.7 mm. ; height, 2.1 mm. ; thickness, .? mm.”— Ruedemann, 1901. This fine ostracod is easily distinguished by its strongly convex valves with a flat, smooth area at the apex of the surface which elsewhere is marked by circular impressions or deep pits. MARYLAND GEOLOGICAL SURVEY 369 Occurrence—CuaMBERSBURG LimEsToNE (Tetradium cellulosum bed). Fort Loudon, Franklin County, Pennsylvania. The type specimens were found in the Rysedorph conglomerate at Rysedorph Hill, Rensselaer County, New York. : Collection.—U. 8S. National Museum. Genus CERATOPSIS Ulrich CERATOPSIS CHAMBERSI (Miller) Plate LV, Fig. 34 Beyrichia chambersi Miller, 1874, Cincinnati Quart. Jour. Sci., vol. i, p. 234, eee aad Hall and Whitfield, 1875, Pal. Ohio, vol. ii, p. 104, pl. iv, figs. 11, 12. Ceratopsis chambersi Ulrich, 1894, Geol. Minnesota, vol. iii, pt. 2, p. 676, pl. xlvii, figs. 19-22. Description.—* Carapace minute, the extreme length not exceeding half a line, and the greatest width not more than two-thirds as much as the length. Form of the valves broad ovate, with one side, for a space equal to about one-fourth of the width of the figure, cut away, forming the straight hinge-line, which is equal in length to about six-sevenths of the entire length of the carapace. Greatest width of the valve a little more than one-third of the length from the anterior end. Surface of the valves highly convex, most prominent near the middle of the length, crossed by three curving sulci, none of which reach the ventral border, the middle of the curve being directed towards the posterior extremity. The middle sulcus is stronger and much deeper than the others, while the posterior one is faintly marked, and situated at about the posterior third of the length. The anterior sulcus is short, comparatively deep, nearly semicircular, and situated within the anterior third of the length, and about midway between the cardinal and basal borders. From the anterior margin of this depression, or between it and the anterior border of the valve, there rises a strong, thickened, lanceolate, or scythe-shaped, curved spine, which equals in length two-fifths, or sometimes one-half that of the entire valve. The anterior and posterior surfaces of the spine are 370 SYSTEMATIC PALEONTOLOGY convex, the latter most strongly so, while the lateral edges are sharp and the ventral one generally deeply serrate, although a few specimens have been noticed without the serrations, perhaps from wearing. The margin of the valve is bordered by a thickened rim, within which there is often a slightly depressed channel. Surface of the crust smooth, or very finely granulose.”—Hall and Whitfield, 1875. ; Occurrence —MARTINSBURG SHALE (Eden division). Southern Penn- sylvania and on the west slope of Rickard Mountain in Maryland. Collections.—Maryland Geological Survey, U. S. National Museum. Genus ULRICHIA Jones ULRICHIA BIVERTEX (Ulrich) Plate LY, Fig. 32 Leperditia bivertex Ulrich, 1879, Jour. Cincinnati Soc. Nat. Hist., vol. ii, p. 11, pl. vii, figs. 5, 5a. Ulrichia ? bivertex Ruedemann, 1912, New York State Mus. Bull., No. 162, p. 120, pl. ix, figs. 11, 12. Description.—* Length, 1.00 mm. ; breadth, .75 mm. Carapace minute, subreniform ; dorsal margin straight, over two-thirds as long as the entire length of the valve; anterior and posterior extremities equal in width; ventral curve nearly uniform. Valves strongly convex. Tubercle at the anterior end, near the dorsal margin large, rising abruptly, obtusely rounded, and slightly directed posteriorly. Posterior tubercle situated near the dorsal margin, and about half the length of the valve from the posterior extremity, less obtusely rounded, and more prominent than the anterior tubercle. Between the tubercles there is a deep sulcus, extending from the dorsal margin to one-half the distance across the valve. ‘Surface smooth. On the interior there is a corresponding pit for each tubercle, and a divisional ridge between them.”—Ulrich, 1879. Occurrence.—MarvTINsBurG SHALE (Eden division). Jordans Knob, one and one-haJf miles northeast of Fort Loudon, Pennsylvania. Collection—U. S. National Museum. MARYLAND GEOLOGICAL SURVEY 371 Family CYPRIDAE Genus BYTHOCYPRIS Brady ByvTHocyPRIS CYLINDRICA (Hall) Plate LV, Figs. 28-31; Plate LIT, Figs. 14-16 Leperditia (Isochilina) cylindrica Hall, 1872, 24th Rep. New York State Cab. Nat. Hist., p. 231, pl. viii, fig. 12 (Extract 1871, p. 7, pl. iv, fig. 12). Bythocypris cylindrica Ulrich, 1894, Geol.. Minnesota, vol. iii, pt. 2, p. 687, pl. xliv, figs. 29-35, p. 688. Description Carapace minute, seldom exceeding two-hundredths of an inch in length, nearly twice as long as wide; valves very convex and cylindrical, the anterior and posterior ends subequal and strongly rounded ; cardinal line much shorter than the length of the valve; tubercle obsolete. Surface smooth.”—Hall, 1872. An abundant fossil in all divisions of the Trenton and Cincinnatian rocks of the United States and Canada. Occurrence —MAntInsBurG SHALE (Eden division). Southern Penn- sylvania and in the debris from the same on Fairview and Rickard Mountains in Maryland. . Collections—Maryland Geological Survey, U. 8. National Museum. Superorder CIRRIPEDIA Family LEPIDOCOLEIDAE Clarke Genus LEPIDOGOLEUS Faber LeprpocoLeus JaMEsI (Hall and Whitfield) Plate LV, Figs. 1-4; Plate LIT, Figs. 24, 25 Plumulites jamesi Hall and Whitfield, 1875, Geol. Surv. Ohio, Pal., vol. ii, p. 106, pl. iv, figs. 1-3. Lepidocoleus jamesi Faber, 1886, Cincinnati Soc. Nat. Hist., vol. ix, p. 15, pl. i, figs. A-F. Lepidocoleus jamesi Ruedemann, 1901, New York State Museum Bull. No. 42, p. 521, pl. ii, figs. 10-12. Description.—“ General form of the plates triangular, with the apex a little inclined to one side, the lateral margins gradually and rapidly diverg- ing from the initial point, one of them considerably longer than the other. BG SYSTEMATIC PALEONTOLOGY Basal margin sigmoidal, the convex portion situated next to the longest lateral face, the concave portion to the shorter, and the shorter lateral margin deflected downwards in some cases (probably the marginal row of plates). “ The surface of the plates is flattened or slightly convex on the sides, and very faintly depressed along the middle, the whole marked by rather closely arranged, annulating, and scaliform transverse lines parallel with the basal or sigmoidal margin, and marking stages of growth. These transverse lines are usually faintest near the apex, and gradually increase in width with the increased growth of the plate, but in some cases they are quite irregular in their distances. “The length from the apex to the basal margin of the plate is usually a little greater than the transverse diameter, and seldom exceeds a sixteenth of an inch, the largest specimens seen not measuring a line in their greatest diameter.”—Hall and Whitfield, 1875. Occurrence. —MarviInsBurc SHALE (Eden division). Jordans Knob, one and one-half miles northeast of Ft. Loudon; Tuscarora Mountain, two and one-half miles southeast of McConnellsburg, Pennsylvania; and in sandstone debris on the east slopes of Rickard Mountain, Washington County, Maryland. Also in the Corynoides bed at Williamsport, Maryland. Collections—Maryland Geological Survey, U. 8. National Museum. Superorder MALACOSTRACA Division PHYLLOCARIDA Family CERATIOCARIDAE Genus CARYOCARIS Salter CARYOCARIS SILICULA 0. sp. Plate LI, Figs. 21-23 Description.—Pod-shaped bodies which have been identified by Salter as the carapace of phyllopods under the name of Caryocaris, are known in the Canadian shales of America, but no more recent species have been MaryYLaNp GEOLOGICAL SurvEY 373 described. The discovery of well-preserved examples of similar phyllo- pods in considerable numbers in the lower part of the Martinsburg shale just above the Sinuites zone is of considerable interest. These Middle Ordovician phyllopods all conform to a single type for which the name Caryocaris silicula is proposed. The species differs from the others of the genus in its narrower or more elongated carapace, and a more nearly equal anterior and posterior extremity. The latter characteristic is so marked that it is difficult to discriminate the two extremities. A complete carapace is about 11 mm. long and 3.5 mm. high. No other portions of the organism than the carapace have been noted. Occurrence—MartinsBurG SHALE (Corynoides bed). Strasburg, Virginia, and in the same zone northward to Chambersburg, Pennsy!- vania. Collections.—Maryland Geological Survey, U. 8. National Museum. PLATE XXIV PAGE OLENELLUS ‘THOMPSONI (Hall) isos csa ce sed ds Hee C466 84% OS FOE KDE Da eO oOaS 339 A large, almost entire individual of this characteristic trilobite with the third segment unusually prolonged. (After Walcott.) Fragments of the free checks or of the segments are the portions most frequently found in the Antietam Sandstone of Maryland. Cambrian. Georgia slate, Parker’s quarry, Georgia, Vermont. 374 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXIV LOWER CAMBRIAN TRILOBITE Olenellus thompsoni Hall. 25 PLATE XXV Figs. 1-4. OBOLLELA MINOR Walcott......... 0. cece eer ee eee were eee e ene 233 1. Cast of pedicle valve, enlarged. 2. Exterior of pedicle valve. 3. Exterior of brachial valve. 4. Cast of interior of brachial valve and edge view of same. Cambrian (Waucoban), near Stissingville, Dutchess County, New York.- Figs. 5-8. HYoLiTHES COMMUNIS BillingS.......... 0... cee e cece ee eee eaee 318 5,6. Lateral views of two specimens, enlarged. 7,8. Transverse sections showing irregularities in thickness of shell. Cambrian (Waucoban), Troy, New York. Fig. 9. ScOLITHUS LINEARIS Haldemann............c cece cece cece ee eeees 276 Fragment of drifted Antietam Sandstone, preserving the tubes of this species. Pebble, five miles southwest of Washington, D. C. Figures 1 to 8 are after Walcott. MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXV LOWER CAMBRIAN. ANTIETAM SANDSTONE FOSSILS. PLATE XXVI PAGE Fig. 1-9. DOLICHOMETOPUS DL. SP....... sec c cece eeeeeee eaters ss oveeves S88 1. A cranidium slightly elongated by pressure from direction indicated by arrow. X 3. . A similar but less distorted cranidium. X 3. . Rock fragment with cranidium of nearly normal shape. X 3. 4. A large cranidium of the same species. Lateral pressure has narrowed the head. X 1.5. 5. A small pygidium of normal shape. X 1.5. 6. A large pygidium of apparently the same species, slightly distorted. X 1.5. 7. Very small undistorted cranidium. X 3. 8. Two cranidia of normal size. The upper head is slightly shortened while the lower one is laterally compressed by pressure from the direction of the arrow, making it appear elongate. xX 3. 9. Three well preserved cranidia with arrow showing direction of pressure. The upper left hand specimen is of another species with broader fixed cheeks. The upper of the two speci- mens on the right is shortened obliquely, the lower one antero- posteriorly. x 3. Cambrian. Elbrook limestone (20 feet above base). Small quarry on eastern outskirts of Waynesboro, Pennsylvania. ow bo 376 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXVI 9 MIDDLE CAMBRIAN. ELBROOK LIMESTONE FOSSILS. PLATE XXVII Figs. 1-5. HEoOrTHis DESMOPLEURA (MeekK)............ cece cece cece eeeee 237 1. Brachial valve enlarged. 2. Pedicle valve, with characteristic surface. 3,4. Cast of pedicle valve and side outline of same. 5. Exterior of pedicle valve showing surface characters. Ordovician (Ozarkian ?), El Paso County, Colorado. Figs. 6-8. SAUKIA STOSEI Walcott............ 0. cece cece cece ee eee ee eeee 351 6. Surface of limestone with cranidia, free cheek, and pygidium weathered out in relief. xX 3. 7. Side view of cranidium and free cheek shown in Fig. 6. xX 3. 8. Another view of cranidium and free cheek shown in Fig. 6. Cambrian (Ozarkian), Conococheague ls., near Scotland, Franklin County, Pennsylvania. Fig. 9. FOSSIL REEF-FORMING CALCAREOUS ALGAE... .. cc ce eee ee cee eeeeees 190 Photograph of a rock mass forming the edge of a reef of fossil algae (Cryptozoon) overlapped by stratified layers of the argillaceous Conococheague limestone. This algal growth developed regular concentric layers in its lower part (A), but these layers or laminae became rather loosely interwoven in the upper portion (B). In the upper righthand corner (C) the overlapping edges of laminated Conococheague limestone may be noted. One- eighth natural size. Cambrian (Ozarkian), Conococheague ls., one mile south of Clear Spring, Maryland. Figures 1 to 8 are after Walcott. 377 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXVII UPPER CAMBRIAN (OZARKIAN). CONOCOCHEAGUE LIMESTONE FOSSILS. PLATE XXVIII PAGE Figs. 1, 2. CRYPTOZOON PROLIFERUM Hall.......... cc cceees sce ecevensace 1. Edge view of a fragment showing the varying diameter of the bodies formed by the undulating layers in this species. At the top the laminae are less undulating and in fact become almost horizontal. This upper portion represents the beginning of a new growth of the organism. 2. Photograph of a fragment illustrating the view which would be seen in a cross-section taken through the middle line of Fig. 1. The variable diameter of the concentric masses is characteristic. Cambrian (Ozarkian), Conococheague. Near crossing of the Norfolk and Western Railroad and turnpike, one mile south- west of Antietam Station, Maryland. 378 189 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXVIII UPPER CAMBRIAN (OZARKIAN). CONOCOCHEAGUE LIMESTONE FOSSILS. PLATE XXIX PAGE Fig. 1. CRYpTOzZOON PROLIFERUM Hall...............0c000. silat Pe dara 324% 189 Photograph of the upper side of a well preserved example of this characteristic fossil, the original of which is 22 inches wide. The unequal size of the confluent heads is a characteristic feature in this species. Cambrian (Ozarkian), Hoyt ls. near Saratoga Springs, New York. Fig. 2, 3. CRyPTOZOON UNDULATUM Bassler 0. SD.......ecceeceseecceuens . 190 2. Edge view of lower portion of a specimen showing the rather evenly undulating layers which form a pseudocolumnar structure. 3. Under side of same specimen illustrating the relatively equal pro- portions of the areas formed by the undulating layers. Cambrian (Ozarkian), Conococheague ls., one mile south of Pleasant Hill School (2% miles southeast of Funkstown), Maryland. 379 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXIX UPPER CAMBRIAN (OZARKIAN). CONOCOCHFAGUE LIMESTONE FOSSILS. PLATE XXX PAGE CRYPTOZOON UNDULATUM Bassler n. Sp..........- Salus womlenne-4 wine eater e oa 190 Edge view of a specimen, two-thirds natural size. In the lower third the laminae are undulated strongly, giving the appearance of vertical columns in cross-section. The undulation is less pro- nounced in the middle third but the laminae are sti!l quite distinct. In the upper third above the black line the distinct lamination disappears and the layers show the beginning of a new growth which is again quite undulating. Cambrian (Ozarkian), Conococheague ls., one mile south of Pleasant Hill School (2% miles southeast of Funkstown), Maryland. 380 CAMBRIAN AND ORDOVICIAN, PLATE XXX MARYLAND GEOLOGICAL SURVEY “STISSOA ANOLSANIT ANOVWAHOOIONOD (NVIMNUVZO) NVIYaWvo wddn PLATE XXXI PAGE Fig. 1. PAL®opHycus TUBULARE Hall....... aii sie ata ebe vag caida aewadeees . 192 View of the cylindrical stems of this species, two-thirds natural size. Ordovician (Canadian), Tribes Hill ls. of New York. Figs. 2-5. OPHILETA COMPLANATA V@NUXEM........ cee cee ee eee cee eens 302 2,3. Top and side views of the type of Pleurotomaria hunterensis Cleland, representing a large specimen of Ophileta complanata. 4,5. Lower and upper views of a smaller specimen. Ordovician (Canadian), Tribes Hill ls.. Fort Hunter, New York. Fig. 6. PLEUROTOMARIA FLORIDENSIS Cleland............. ses ce cece reese Enlarged view of the type example. Ordovician (Canadian), Tribes Hill ls, Fort Hunter, New York. Figs. 7-12. DALMANELLA WEMPLEI Cleland........... 0. cece ee ee eee eeeeee 7. A large brachial valve. X 2. 8,9. Two pedicle valves with side outline of one. X 2. Ordovician (Canadian), Kittatinny ls., Columbia, New Jersey. 10. Brachial valve. 11,12. Two pedicle valves, showing alternation of coarse and fine costae. ; Ordovician (Canadian), Tribes Hill ls., Fort Hunter, New York. Figs. 13, 14. RIBerRIA NUCULITIFORMIS Cleland.............. ccc eee eee eee 13. Lateral view of well preserved cast showing the notch. 14. Posterior view of a cast. Ordovician (Canadian), Tribes Hill ls., Fort Hunter, New York. Figs. 15-17. RAPHISTOMA ? OBTUSUM Cleland.............. es eee ee eeeees Upper, side, and lower views of the type, enlarged. Ordovician (Canadian), Tribes Hill ls., Fort Hunter, New York. Figs. 18, 19. OPHILETA LEVATA VaDUXeEM............ see cece eee eee eeee Top and side views of the type of Ophileta discus Cleland determined by that author to be the same as Ophileta levata. Ordovician (Canadian), Tribes Hill ls., Fort Hunter, New York. Figs. 20, 21. EccLioMpHALUS MULTISEPTARIUS Cleland...............0008 20. Top view of the type. 21. Natural section showing the partitions. Ordovician (Canadian), Tribes Hill ls., Fort Hunter, New York. Figs. 22, 28. RAPHISTOMA COLUMBIANUM Weller...........-ececceceeees : Top view and side outline of the type example. Ordovician (Canadian), Kittantinny 1s., Columbia, New Jersey. Fig. 1 after Hall, 2-6, 10-21 after Cleland, and 7-9, 22-23 after Weller. 381 291 246 362 307 304 305 307 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXXI FOSSILS OF BEEKMANTOWN LIMESTONE (STONEHENGE MEMBER). PLATE XXXII PAGE Figs. 1, 2. CyRTOCERAS BEEKMANENSE Whitfield........ eld Piite lene SHEN B00 . 1. Lateral view of an incomplete shell, showing septa and living chambers. 2. Ventral view of same specimen. Ordovician (Canadian), Beekmantown ls. (Division D. 1), Beekmantown, N. Y. Figs. 3, 4. CyrTOCERAS GRACILE Cleland............. cece cee ec cen eeeenes Ventral and lateral views of the type. Ordovician (Canadian), Tribes Hill ls.. Fort Hunter, New York. Fig. 5. ORTHOCERAS PRIMIGENIUM Vanuxem........... Be Sad SeinevaniSae deur eee oes Natural longitudinal section, illustrating tapering of shell and close- ness of septa. Ordovician (Canadian), Beekmantown ls., Beekmantown, New York. Figs. 6, 7. CYCLOSTOMICERAS CASSINENSE (Whitfield).................. Lateral and ventral views of a young specimen preserving only the living chamber and several septa. Ordovician (Canadian), Beekmantown ls., Cassin beds, Fort Cassin, Vermont. Figs. 8-10.. ASAPHELLUS GYRACANTHUS Raymond............ecceeeeceece 8. Pygidium. 9. Free cheek. 10. An imperfect cranidium. Ordovician (Canadian), Tribes Hill ls., Fort Hunter, New York. Figs. 11-15. HEMIGYRASPIS COLLIEANA Raymond............cececeeeeeere 11. An imperfect cranidium. 12. A free cheek. X 2. 13. Well preserved pygidium. 14, An imperfect pygidium. 15. Hypostoma. Ordovician (Canadian), Stonehenge ls., Bellefonte, Pennsyl- vania. Figs. 16-18. SyMPHYSURUS CONVEXUS (Cleland)............e. ee ceeeeee hie 16. The cranidium figured by Weller as Illaenurus columbiana. Ordovician (Canadian), Kittatinny ls., Columbia, New Jersey. 17, 18. Two small pygidia. Ordovician, Tribes Hill ls., Fort Hunter, New York. Figs. 19, 20. Ooceras KIRBYI (Whitfield) ........... cc cece eee eee eens ae 19. Lateral view of the type. 20. View of the outer chamber separated from the shell to show depth of the septum. Ordovician (Canadian), Beekmantown ls. (Division D. 1), Beekmantown, New York. Figs. 1, 2, 5, 19, 20 are after Whitfield; 6, 7 after Ruedemann; 3, 4 after Cleland; and 8, 18 after Raymond. 382 330 329 322 331 345 346 347 328 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXXII FOSSILS OF BEEKMANTOWN LIMESTONE (STONEHENGE MEMBER). 26 PLATE XXXIII PAGE Figs. 1-3. OPHILETA COMPACTA Salter.......... 0c. cece cece eee tee eee eee . 804 1,2. Lower and upper sides of a specimen. 38. Schematic cross-section of the same. Ordovician (Canadian), Beekmantown ls., Beekmantown, New York. Figs. 4, 5. SYNTROPHIA LATERALIS Whitfield............ 0.0: cece sce eeeeee 267 4. Pedicle valve. xX 2. 5. Sketch of hinge of same. Ordovician (Canadian), Kittatinny ls., Columbia, New Jersey. Figs. 6, 7. ECCLIOPTERUS TRIANGULUS (Whitfield) .............. 2. ee eeee 302 6,7. Top and side views of a cast of the interior. Ordovician (Canadian), Beekmantown ls., Providence Island, Vermont. Figs. 8, 9. MACLURITES AFFINIS (Billings) .......... 0. ccs cece eee e ee eens 297 8. Top view. 9. Cross-section of the shell. Ordovician (Canadian), Division F of Quebec group. Keppel Island, Newfoundland. Figs. 10-12. Hysrricurus conicus (Billings) ............ 0... cc cee eee nee 340 10. Glabella. x 2. : 11. Pygidium. xX 2. 12. Profile of glabella in outline. Ordovician (Canadian), Beekmantown ls., Beekmantown, New York. Figs. 13-15. TrrraDIUM SIMPLEX Bassler N. SP......... cece eee cee ee eeee 199 18. Weathered fragment of limestone showing edge view of tubes. 14. Top view of corallum. 15. Portion of same. X 4. Ordovician (Canadian), lower part of the Beekmantown ls. just above the Stonehenge member, eastern edge of Hagerstown, Maryland. Figs. 1-3, 10-12 are after Whitfield; 4, 5, after Weller; 6, 7, after Ulrich; and 8 and 9 after Billings. MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXXI1IP FOSSILS OF BEEKMANTOWN LIMESTONE (CRYPTOZOON STEELI ZONE). PLATE XXXIV PAGE Fig. 1. CRYPTOZOON STEELI Seely. ..... 0.0... ccc e cece cence eee eeetseeeces 191 A small weathered, rounded specimen. Ordovician (Canadian), Cryptozoon steeli zone of the Beek- mantown Is., near Williamsport, Maryland. Fig. 2. OPHILETA COMPACTA Salter... ... 0. ccc cece eee cence tee ceneeeeeer 804 Casts of two examples embedded in the rock. Ordovician (Canadian), Cryptozoon steeli zone of the Beek- mantown lIs., Paradise Church, Maryland. Wig. 3:, LICGYMOMPHALUS (8D, esc ss cihsx's.c-aiene oo 8 ccash, 455 Aceiace 26a aveae See Rie Pag are oe 305 Specimen of a small narrow species. The ridges running across the shell are calcite-filled fractures of the rock. Ordovician (Canadian), Beekmantown ls., near Paradise Church, Maryland. Figs 4,. IECCYLIOMPHALUS: SDi icles «sie e dnnaiees eel sa bhi Sa ainiel se Dew HIN 805 Sections of several examples of an undetermined, large, loosely- coiled gastropod shell. Ordovician (Canadian), Beekmantown ls., lower part, Hagers- town, Maryland. Fig; 6. CYRTOCERAS: ? SDiiwsag sc sned eo ee eae ks eee ke ge Pate es nee Sas dese ei 329 View of a curved cephalopod showing appearance on a weathered sur- face. In the fresh rock all trace of the structure is generally gone. Ordovician (Canadian), Lower Stonehenge division of the Beekmantown ls., near Funkstown, Maryland. _ Figures 3, 4 and 5 are introduced to show the usual aspect of the fossils found in the Beekmantown limestone of Maryland. 384 CAMBRIAN AND ORDOVICIAN, PLATE XXXIV MARYLAND GEOLOGICAL SURVEY : a &, rn FOSSILS OF BEEK MANTOWN LIMESTONE (CRYPTOZOON STEELI ZONE). PLATE XXXV Figs. 1-8. PLEUROTOMARIA ?? GREGARIA Billings..........ceeceececceeees 290. 1, 2. Side view of an example enlarged and natural size. 3. Another view of the same. Ordovician (Canadian), Beekmantown ls., St. Ann, Canada. Figs. 4, 5. HorMoTOMA GRACILENS (Whitfield) ........... 0... 0c cece ce eee 293: Two nearly complete specimens. Enlarged. Ordovician (Canadian), Beekmantown ls. (Division D), Beek- mantown, New York. Fig. 6. DALMANELLA ELECTRA (Billings) ........... 0.20 c cece cece ce eeces 245 Pedicle valve. xX 2. Ordovician (Canadian), Kittatinny ls., Columbia, New Jersey. Figs. 7, 8. MACLURITES OCEANUS (Billings) .............. cee ce eee ae eens 299 Top and side views of the type. Ordovician, Quebec group, Port aux Choix, Newfoundland. Figs. 9,10. EccyLiopTerus DISJUNCTUS (Billings) ..............0 eee eens 301 9. View of the spire. 10. Lower side of the shell. Ordovician (Canadian), Beekmantown ls., Leeds and Gren- ville counties, Canada. Fig. 11. TurritomMa AacrEA (BillingS)........... 0... ccc cece cee eee eee 293 Drawing of the type specimen natural size. Ordovician (Canadian), Division G of Quebec group, Port aux Choix, Newfoundland. Fig. 12. ISOCHILINA SEELYI Whitfield. ...... 0... . cc ccc cee ccceeencvcceves 363. View of a right valve with lateral and ventral edge views. xX 4. Ordovician (Canadian), Beekmantown ls., Providence Island, Lake Champlain, Vermont. Fig. 18. CyRTOCERINA MERCURIUS BillingS.......... 0... cc cece eee eee e eens 331 Side view of the type specimen. Ordovician (Canadian), Point Levis, Quebec. Fig. 14. TRoCHOLITES INTERNISTRIATUS Whitfield..................0000- . 326 Lateral view of specimen showing surface sculpture of the various stages of the shell. Ordovician (Canadian), Beekmantown ls., Cassin beds, Fort Cassin, Vermont. Fig. 15. CAMEROCERAS and CYRTOCERINA... 0... cece cece cece cette teen ee: 331 A group of specimens showing occurrence and condition of preserva- tion of these cephalopods in Maryland strata. The two left- hand views represent a species of Cyrtocerina. The remaining figures are of an undetermined species of Cameroceras. These fossils occurred as imperfectly silicified, iron-stained pseudo- morphs on the weathered edges of rifts and caves in the lime- stone. Ordovician (Canadian), Beekmantown ls., quarries at Legore, Maryland. Figs. 1-3, 7-11, and 13 are after Billings; 4, 5, 12 are after Whitfield; 6 after Weller; and 14 after Ruedemann. 385 CAMBRIAN AND ORDOVICIAN, PLATE XXXV MARYLAND GEOLOGICAL SURVEY FOSSILS OF THE BEEKMANTOWN LIMESTONE. PLATE XXXVI Figs. 1-3. MACLURITES SORDIDUS (Hall) ........ ccc cae eee e reece cereeees 1,2. Lower side of two specimens. 3. Upper side of a partial cast. Ordovician (Canadian), Beekmantown ls., Beekmantown, New York. Figs. 4,5. PLEUROTOMARIA ?? CANADENSIS BillingsS.............cceceeeoes : 4. Side view of a cast. 5. View showing spire of specimen with shell preserved. Ordovician (Canadian), Beekmantown ls., Leeds and Gren- ville counties, Canada. Figs. 6,7. RApPHISTOMINA LAURENTINA (Billings) ............ 0.0 ee eeeeeee 6. Side view. 7. Top view of a cast. Ordovician (Canadian), Romaine formation, Mingan Islands, Canada, Figs. 8, 9. HorMoToMA ARTEMESIA (Billings) ........... ccc ee eee e cess 8. Cast of the interior of a fragment. 9. A partly restored, well preserved specimen. Ordovician (Canadian), Beekmantown ls., Leeds and Gren- ville counties, Canada. Figs. 10-12. ISoOCHILINA GREGARIA Whitfield............ ccc ce cece e ee eens . 10. View of right valve and outline showing elevation. X 4. 11. Left valve of a larger example, with sketch of outline. xX 4. 12. Internal cast of right valve and outline. xX 4. Ordovician (Canadian), Beekmantown ls., east shore of Lake Champlain, Vermont. Fig. 138. PLIOoMEROPS SALTERI (Billings).............0eee08 oo BRuneadensha recces Pygidium. Enlarged. Ordovician (Canadian), Beekmantown Is., Phillipsburg, Quebec. Fig. 14. GonruRUS CAUDATUS (Billings) ....... 0... ccc cece eee ee eeeee Pygidium, illustrating the large triangular spine. Ordovician (Canadian), Division G and H of the Quebec group. Port aux Choix, Newfoundland. Fig. 15. CERATOPEA KEITHI Ulrich........... ccc cece cece eect eens eeees et Side and edge views of a group of specimens. Ordovician (Canadian), Beekmantown, Ceratopea zone, western edge of Bristol. Tennessee and Wytheville, Virginia. Figs. 1-3, 10-12 are after Whitfield; 4-9, 18, and 14 are after Billings. 386 289 308 291 363 359 340 299 CAMBRIAN AND ORDOVICIAN, PLATE XXXVI MARYLAND GEOLOGICAL SURVEY FOSSILS OF THE BEEKMANTOWN LIMESTONE. PLATE XXXVII Figs. 1-4. STROPHOMENA STOSEI Bassler 0. SP.......-- eee eee cece cece ecees 1. A brachial valve and interior of a brachial valve nearby. X 2.5. 2. A pedicle valve of a specimen referred to this species doubtfully on account of its high hinge area. X 2.5. 8. A crushed pedicle valve. X 2.5. 4, Fragment of a larger shell referred to the species. Ordovician (Chazyan), Frederick l|s., stone fences just east of Frederick, Maryland. Fig; 5. RETEOCRINUS: PSP, UDGCb sic. esas sess xia hel siee bee eH ES ele Fe se A plate-like structure with seven rays. X 6. Other examples exhibit only six rays. None of the specimens shows a basal portion con- necting the rays. Ordovician (Chazyan), Frederick ls., just east of Frederick, Maryland. Figs. 6-8. ACIDASPIS ULRICHI Bassler 0. SP..... 2... eee eee cee ee eee eee Three specimens illustrating the unusual development of long spines not only along the free cheeks but even to the tip of the genal spine, and the extraordinary curvature suggesting that the spines were directed over the thorax. X 2. Ordovician (Chazyan), Frederick Is., east of Frederick, Mary- land. Fig: 9. ISOTELUS SPs UNGEE. 65 oer scdsan yea Gi sn ROGAViteeaes See Ses ESS Imperfect free cheek. X 1.5. Ordovician (Chazyan), Frederick ls., east of Frederick, Mary- land. Bigs 10) (CAMEROCERAS (SDs) ae es h5G/s 5b tale Svenea e's deiauels wie alesse eee oo HORS Endosiphuncle composed of crystalline matter, embedded in limestone. Ordovician (Chazyan), Frederick ls., east of Frederick, Mary- land. 387 209 355 345 321 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXXVII FOSSILS OF THE FREDERICK LIMESTONE, PLATE XXXVIII Figs. 1-5. HeBERTELLA VULGARIS RayMond...........e cece rere eee e en eees 239 1-2. Three views of a small specimen with direct striae. 4,5. A large specimen exhibiting some bifurcating striae. Ordovician (Chazyan), Chazy, New York. Figs. 6-8. DirnorTHIs (PLAESIOMYS) PLATYS (Billings)............... we. LAT 6. Brachial valve. 7. Edge view of shell. 8. Pedicle valve. Ordovician (Chazyan), Montreal, Canada. Figs. 9-12. HEBERTELLA BOREALIS (Billings) ...........0ce ce eee rece ence 9-11. Three views of a specimen. 12. An example with very short hinge line. Ordovician (Chazyan), near Montreal, Canada. Figs. 13-15. TETRADIUM SYRINGOPOROIDES Ulrich............. Ee isis 18. Surface of a weathered slab showing usual aspect of the species. 14. Portion of the same illustrating tubes in more detail. X 3. 15. Drawing of a transverse section illustrating the usual appearance of the tubes (at the top), the development of the characteristic four septa (in the middle), and two tubes still united (at bottom of figure). X 6. Ordovician (Chazyan), upper part Stones Rives ls., Pinesburg Station, Maryland. Figs. 1-5, 9-12 are after Raymond and 6-8 are after Billings. 388 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXXVIII FOSSILS OF THE STONES RIVER LIMESTONE. PLATE XXXIX Figs. 1.5. LopHoSpira BICINCTA (Hail).......... ccc cece eee eecceeeneees 294 1. A perfect, silicified shell. 2. Portign of the last whorl of same, showing direction and regularity of lines of growth. X 2. 3. Right side of last whorl of Fig. 1. Ordovician (Chazyan), Stones River ls., Murfreesboro, Ten- nessee. 4, A large cast of the interior on which some of the external lines of growth are obscurely preserved. Ordovician (Chazyan), Black River group, Beloit, Wisconsin. 5. Vertical section of an elongated specimen. Ordovician (Chazyan), Black River group, Dixon, Illinois. Figs. 6-8. BUCANIA SULCATINA (HMMOMNS)...........0 ccc eee cece eee enee 309 6. Side view of a large individual. 7. View of a specimen. X 2. 8. A young individual. X 6. Ordovician (Chazyan), Lake Champlain area. Figs. 9-11. Ampyx (LONCHODOMAS) HALLI (Billings).................... 337 9. Head with rostral spine broken. 10. Pygidium with two of thoracic segments. 11. Side view of head. Ordovician (Chazyan), Highgate Springs, Vermont. Figs. 12-15. MAcLURITES MAGNUS LeSUeUL........... eee e eee ee eee eee 297 12-14. Top, side, and botttom views of same specimen, two-thirds natural size. 15. Interior view of an operculum, two-thirds natural size. Ordovician (Chazyan), Lake Champlain area. Fig. 16. LePerDIcIaA FABULITES Conrad Var......... eee ee eee eee eee eee 364 Surface of slab with numerous examples of this variety. X 1.3. Ordovician (Chazyan), Stones River group, Lebanon ls., Columbia, Tennessee. Figs. 1-5 are after Ulrich and Scofield; 6-8, 12-14 are after Raymond; and 9-11 are after Billings. MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XXXIX FOSSILS OF THE STONES RIVER LIMESTONE. PLATE XL Figs. 1-8. HELOPORA DIVARICATA Ulrich. ......... 0c cece cece eee eee ceeeces 1. Segment natural size and xX 7. 2. Portion of the same. X 18. 8. Transverse section. xX 18. Ordovician (Mohawkian), Black River (Decorah) shales, Minneapolis, Minnesota. Figs. 4-6. CHASMATOPORA RETICULATA (Hall).............cecee ees eeeeees 4. Frond showing the reverse side. 5. Portion of the same. x 9. 6. Small fragment exhibiting the reverse or celluliferous side. X 18. Ordovician (Mohawkian), Trenton shales, Minneapolis, Minnesota. Figs. 7-10. CHASMATOPORA SUBLAXA (Ulrich) ........... cc cece eee cece eee 7,8. Fragments showing obverse and reverse sides. 9. Celluliferous side of specimen, Fig. 7. X 9. 10. Reverse side of small fragment, Fig. 8, illustrating striated char- acter. xX 9. Ordovician (Mohawkian), Black River (Decorah) shales, Minneapolis, Minnesota. Figs. 11-14. EscHAROPORA CONFLUENS Ulrich............. ccc cece eee eens 11. A specimen preserving the pointed articulating base. 12. Surface of example illustrating arrangement of apertures. xX 9. 13. Vertical section. X 18. 14, Tangential section of a well preserved fragment. X 18. Ordovician (Mohawkian), Black River (Decorah) shales, Minneapolis, Minnesota. Figures after Ulrich. 390 226 227 223 CAMBRIAN AND ORDOVICIAN, PLATE XL MARYLAND GEOLOGICAL SURVEY n FOSSILS OF THE CHAMBERSBURG LIMESTONE (CARYOCYSTITES BED). 27 PLATE XLI Figs. 1-3. SoLENOPORA COMPACTA BillingS........... cece eee ee reece eeeeee 192 1. View of a small mass. 2,3. Longitudinal and transverse sections. X 35. Ordovician (Mohawkian), Black River (Decorah) shales, near Cannon Falls, Minnesota. Fig. 4. TeTRADIUM COLUMNARE (Hall)............ cece cece cece eee e eens 201 Fragment of a corallum. Ordovician (Mohawkian), Trenton ls., Lewis County, New York. Fig. 5. CoLUMNARIA HALLI Nicholson.......... ccc cee cece ect e cece eeenees 198 Corallum showing the little extension of the septa in the tubes. Ordovician (Mohawkian), Trenton ls. of Canada. Fig. 6. HEBERTELLA BELLARUGOSA (Conrad) .........c cece cece cece eeceeee 239 Exterior of a brachial valve. Ordovician (Mohawkian), Trenton shales of Minnesota. Fig. '1.. CARYOCYSTLDES® SD vice sedis 6 espe oo Xian VA Dalla a WN Twa wee RANT Soi 208 A weathered plate of this cystid showing the pores. xX 4. Ordovician, Caryocystites bed of the Chambersburg ls., Fort London, Pennsylvania. Figs. 8, 9. RAFINESQUINA CHAMPLAINENSIS Raymond..............0e00e . 261 8. Specimen exhibiting brachial valve, cardinal area, and deltidium. 9. Pedicle valve. Ordovician (Chazyan), New York. Fig. 10. CARABOCRINUS SD............ gba ods apaseccaos Sona teNE abate Senda Roa 209 An imperfect plate. Ordovician, Caryocystites bed of Chambersburg ls., Fort London, Pennsylvania. Figs. 11-138. LepTaENA CHARLOTTAE Winchell and Schuchert.............. 257 Views of the pedicle and brachial valve and side outline of the same specimen. Ordovician (Mohawkian), Black River (Decorah) shales, St. Paul, Minnesota. Figs. 14-16. CAMAROTOECHIA PLENA (Hall)........... cece cece cece er eceee 270 Views of the pedicle and brachial valves and side outline of an average specimen. Ordovician (Chazyan), Canada. Fig. 17. HeEperTELLA BOREALIS (Billings)................ ee ee .. 238 An example showing the pedicle valve. Ordovician (Chazyan), near Montreal, Canada. Fig. 18. HEBERTELLA VULGARIS Raymond........... sai blade ous daiss pees 239 Pedicle valve of a large example. X 2. Ordovician (Chazyan), New York. Fig. 19. GonrocerRaAs CHAZIENSE Ruedemann........... equlavadiweneviss: sae ei ene O28 An imperfect specimen showing the arrangement of the septa. Ordovician, Carocystites bed of the Chambersburg ls., Fort Loudon, Pennsylvania. Figs. 1-3, 6, 11-13, are after Winchell and Schuchert; 4 after Hall; 5, 14-16, after Billings; and 8, 9, 17, 18, after Raymond. 891 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XLI oe s3 oA CO aN ie esd DATA T AS {7 x BETS prep FOSSILS OF THE CHAMBERSBURG LIMESTONE (CARYOCYSTITES BED). PLATE XLII PAGE Figs. 1, 2. STREPTELASMA PROFUNDUM (Comrad)..........ceceeceececeees 1. An entire specimen with a portion broken away to show the great depth of the body cavity. 2. View of the body cavity. Ordovician (Mohawkian), Black River (Platteville) ls., Mineral Point, Wisconsin. Figs. 3-5. TETRADIUM CELLULOSUM (Hall) .......... cc cece cece eee ene eeee 8. Section in the rock cutting the tubes longitudinally and showing their arrangement in bundles. 4. Portion of two bundles, enlarged. 5. Cross-section in rock, exhibiting the arrangement of the tubes and the occurrence of the characteristic four septa. Ordovician (Mohawkian), Black River ls., Watertown, N. Y. Fig. 6. CAMAROCLADIA RUGOSA UIPich......... cece cece eee eee ee enee Rock fragment composed almost entirely of the branches of this organism. Ordovician (Mohawkian), Black River (Decorah) shales, St. Paul, Minnesota. Figs. 7, 8. ORBIGNYELLA WETHERBY! (Ulrich).............. 0. cee eee eeeee 7. Vertical section exhibiting the characteristic curved diaphragms. xX 18. 8. Tangential section showing the angular tubes and the granular walls. X 18. Ordovician (Mohawkian), Black River (Platteville) ls., Minneapolis, Minnesota. Figs. 9-12. ZyYGOSPIRA RECURVIROSTRIS (Hall)........... cc see ecw cece eee 9, 10. Brachial and pedicle valves of an entire specimen. X 2. 11, 12. Anterior and lateral views of the same. Ordovician (Mohawkian), Trenton portion of the Jackson- burg, Is., Jacksonburg, New Jersey. Figs. 13-15. HELicoTOMA PLANULATOIDES Ulrich........... sts i 3 6 xa 4-4 RC Re Three views of an entire silicified specimen. Ordovician (Mohawkian), Black River (Lowville) ls., Mercer County, Kentucky. Figs. 16, 17. HELICOTOMA VERTICALIS Ulrich............. cece cece ee eees ‘ Basal and lateral views of a cast of the interior. Ordovician (Mohawkian), Black River (Lowville) ls., High Bridge, Kentucky. ‘Figs. 18-20. CTENODONTA GIBBERULA Salter........ sce cece cece cee eeee x 18. Lateral view of a large right valve. 19. Cardinal view of the same. Ordovician (Mohawkian), Stones River (Murfreesboro) ls., Murfreesboro, Tennessee. Fig. 1, 2 are after Winchell and Schuchert; 3-5 are after Hall; 7, 8, 18-20 are after Ulrich; 9-12 are after Weller; and 13-17 are after Ulrich and Scofield. 199 202 196 214 272 300 301 277 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XLIP € SY iD FOSSILS OF THE CHAMBERSBURG LIMESTONE (TETRADIUM CELLULOSUM BED), PLATE XLIII PAGE Figs. 1-5. LePERDITIA FABULITES (Conrad) ......-... 0.0 cece ee eee eee ones 1. Cast of interior of right (larger) valve showing impressions of papillae along ventral margin. X 2. . 2,3. Ventral and dorsal views of a complete carapace. X 2. 4. Left valve of the same. X 2. 5. Posterior view. X 2. Ordovician (Mohawkian), Black River (Platteville) ls., Minneapolis, Minnesota. Figs. 6-9. MACRONOTELLA ULRICHI Ruedemann............eeeeeeeeeeees 6,7. Ventral and lateral views of a large valve. X 14. 8,9. Similar views of another specimen showing the specific char- acters well developed. X 14. Ordovician (Mohawkian), Rysedorph conglomerate, Ryse- dorph Hill, Rensselaer County, New York. Figs. 10-12. LeEperDITELLA TUMIDA (Ulrich)...... Shiela ch erste tacoma Nene Wigubeears 10. Right valve. x 10. ; 11,12. Dorsal and posterior views of same in outline. X 10. Ordovician (Mohawkian), Black River (Lowville) ls., High Bridge, Kentucky. Figs. 13-15. DREPANELLA MACRA Ulrich.............. cece eeeeeeeeeeeeene 13. Left valve. xX 20. 14, 15. Sectional views of same between points marked c and b. Ordovician (Mohawkian), Stones River (Lebanon) ls., La- vergne, Tennessee. Figs. 16, 17. OMosprmra ALEXANDRA (Billings)............ 0.000 cceceeeuee 16. Cast of the interior. Ordovician (Mohawkian), Black River (Platteville) is., Dixon, Illinois. 17. An imperfect, silicified shell. Black River (Lowville) ls., Mercer County, Kentucky. Figs. 18-21. PTeERYGOMETROPUS CALLICEPHALUS (Hall).............000000: 18. A nearly complete pygidium of large size. 19. A small complete pygidium. 20. An incomplete head. Ordovician (Mohawkian), Trenton portion Jacksonburg ls., Jacksonburg, New Jersey. 21. Complete individual. Ordovician (Mohawkian), Trenton ls. of Canada. Figs. 22, 23. CrRAURUS PLEUREXANTHEMUS GYIeeN.........cccccceeceeeece 22, An incomplete cranidium. Ordovician (Mohawkian), Trenton portion of Jacksonburg ls., Jacksonburg, New Jersey. 23. General aspect of species of this type. The original of this figure has since been referred to a new species, C. dentatus Raymond and Barton. Trenton ls., of Canada. Figs. 1-5, 10-15 are after Ulrich; 6-9 after Ruedemann; 16, 17, 21, 23 after Billings; 18-20, 22 after Weller. 393 364 368 366 367 308 360 358 CAMBRIAN AND ORDOVICIAN, PLATE XLIII MARYLAND GEOLOGICAL SURVEY nh hie 6 © AYA ARS FOSSILS OF THE CHAMBERSBURG LIMESTONE (TETRADIUM CELLULOSUM BED) PLATE XLIV Figs. 1-5. HEMIPHRAGMA IRRASUM (Ulrich)...........cccceceeeeecsueuee 1. Surface of a zoarium illustrating the usual aspect. x 10. 2. Tangential section. Xx 18. 3. Vertical section exhibiting incomplete diaphragms in mature zone. x 9. 4,5. Two specimens of the branching zoarium. Ordovician (Mohawkian), Black River (Decorah) shales of Minnesota. Figs. 6, 7. DIANULITES PETROPOLITANUS DybowSKki............0ceeecceeve 6. Vertical section. x 9. 7. Tangential section X 9 and a portion X 35 showing wall structure in detail. Ordovician (Mohawkian), Trenton shales, Goodhue County, Minnesota. Figs. 8-10. HELOPORA SPINIFORMIS Ulrich............. cece cece renceecece 8. A segment natural size and lower portion of same. xX 18. 9,10. Vertical and transverse sections of a segment. X 18. Ordovician (Mohawkian), Stones River (Lebanon) ls., La- vergne, Tennessee. Figs. 11-14. RHINMICTYA NEGLECTA Ulrich............. 0c ccc een eee ecenee 11. Fragment, natural size, and portion of surface X 18, showing the usual aspects of the species. 12. Tangential section. x 18. 13,14. Vertical and transverse section. xX 18. Ordovician (Mohawkian), Trenton ls., Burgin, Kentucky. Figs. 15-17. PRASOPORA INSULARIS UITich............ccc cece cece eee cece 15. Tangential section exhibiting the numerous mesopores. X 18. 16. Small portion of a tangential section through a macula and sur- rounding zoecia. xX 18. 17. Vertical section illustrating great abundance of cystiphragms and diaphragms. X 18. Ordovician (Mohawkian), Trenton shales near Cannon Falls, Minnesota. Figures are after Ulrich. 394 217 228 229 215 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATEGXLIV 2 c-e? Leeks Oa ° e YU Ny pe iy) = i} (] vs ent bes EN stl eht cls TON LL ny 5 17 FOSSILS OF THE CHAMBERSBURG LIMESTONE (ECHINOSPHERITES BED). PLATE XLV PAGE Figs. 1-3. PIANODEMA SUBEQUATA (Conrad)........ Veedwew tes eS eae S . 249 Pedicle and brachial valves of a well preserved example and profile of the same. Ordovician (Mohawkian), Black River (Decorah) shales, Minneapolis, Minnesota. Fig. 4. RAFINESQUINA MINNESOTENSIS (Winchell) .............eeeee0e: .. 261 Brachial valve of the type form of this species. Ordovician (Mohawkian), Black River 1s., Rocktown, Wis- consin. Figs. 5, 6. RAFINESQUINA MINNESOTENSIS INQUASSA (Sardeson)......... . 264 Dorsal and profile views of an ordinary example of this variety. Ordovician (Mohawkian), Black River (Platteville) ls., Mineral Point, Wisconsin. Fig. 7. RECEPTACULITES OCCIDENTALIS Salter.......... cc cece cece cece eeee 194 Weathered surface of an imperfect specimen. Ordovician (Mohawkian), Black River portion of Jackson- burg ls., near Springdale, New Jersey. Figs. 8, 9. DINORTHIS PECTINELLA (EMMOMS)............cccececcccceece 248 8. Pedicle valve. 9. Incomplete brachial valve. Ordovician (Mohawkian), Lowest Trenton portion of Jackson- burg Is., near Newton, New Jersey. Figs. 10-12. HEBERTELLA BELLARUGOSA (Conrad) ...........0eceeeeeeeees . 239 10. Exterior of a large pedicle valve. 11. Interior of the same. 12. Exterior of a dorsal valve of the ordinary size. Ordovician (Mohawkian), Trenton shales of Minnesota. Figs. 18, 14. Ampyx (LoNcHODOMAS) NORMALIS (Billings)............... 336 Head and pygidium. 3 Ordovician, Chazyan of Newfoundland. Figs. 15-20. EcHINOSPHERITES AURANTIUM Var AMERICANUM Bassler n. var. 207 15. A specimen of average size showing the ovate form of this variety. 16. A well preserved small example preserving the point of attach- ment at the base. X 2. 17. A slightly distorted but otherwise typical specimen. _ 18. Compressed example with plates exposed by weathering. 19. Abraded outer surface of the plates showing pore rhombs. X 3. 20. Inner surface of calyx plates exhibiting pores. X 3. Ordovician (Mohawkian), Echinospherites bed of Chambers- burg ls., 34% miles north of Greencastle, Pennsylvania. Figs. 1-3, 5, 6, 10-12 are after Winchell and Schuchert; 7-9 after Weller; and 13, 14 after Billings. 395 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XLV 17 FOSSILS OF THE CHAMBERSBURG LIMESTONE (ECHINOSPHERITES BED). PLATE XLVI PAGE Figs. 1-5. NIDULITES PYRIFORMIS Bassler.............eeececceeeeceeeseee 193 1. A nearly complete example partially embedded in limestone. The pyriform shape of the organism is shown. . Surface of same showing the usual aspect of the cups. X 4. 3. A group of examples on a limestone slab with their interior filled with crystalline calcite. : . A fractured piece of limestone with cross-sections of this organism. 5. Weathered rock surface with Nidulites in various positions. Ordovician (Mohawkian), Nidulites bed of Chambersburg ls., Strasburg, Virginia. bw > 396 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XLVI CHAMBERSBURG LIMESTONE ( NIDULITES BED). PLATE XLVII PAGE Figs. 1-38. ScENIDIUM ANTHONENSE Sardeson..........ececeeseecceeees .. 268 1. A complete brachial valve. x 2. 2. Incomplete pedicle valve. X 2. 3. Profile of same. xX 2. Ordovician (Mohawkian), Black River portion of the Jackson- burg ls., Jacksonburg, New Jersey. Figs. 4-6. ORTHIS TRICENARIA Comrad........ 0c. ccc eeee ccc ee ce teteeeeene 240 Brachial and pedicle valves of a complete example and profile view of same. Ordovician (Mohawkian), Black River (Decorah) shales, Minneapolis, Minnesota. Figs. 7,8. PRASOPORA CONTIGUA UITich.......... 0. cece eee eee eee en eee 7. Tangential section of the hemispheric zoarium, showing the com- parative fewness of mesopores. xX 16. 8. Vertical section illustrating the occurrence of cystiphragms and also the small number of mesopores. X 18. Ordovician (Mohawkian), Black River (Decorah) shales, Goodhue County, Minnesota. : Figs. 9-11. DipLorrypa ? APPALACHIA Bassler n. SP.......... eee e cece eee 9. View of the hemispheric zoarium, basal side up in the rock. 10. Tangential section. xX 10. 11. Vertical section. xX 10. ; Ordovician (Mohawkian), Nidulites bed of Chambersburg ls., Strasburg, Virginia. Figs. 12-14. CoRyNOTRYPA DELICATULA (JAMES) ..... 0. eee ec eee cee eeee 12. Zoarium illustrating the elongate club-shaped, incrusting zoccia. xX 9. 13. Several zowecia of the same zoarium more slender than usual. X 25. 14. Unusually large zocecia of another form of the species. X 25. Ordovician (Mohawkian), Black River (Decorah) shales, St. Paul, Minnesota. Figs. 15-17. CoRYNOTRYPA INFLATA (Hall).......... cc cece cece eee eee eeee 15. Small portion of a large zoarium growing upon a brachiopod. X 9. 16. Three zocwcia of one form of the species. X 18. 17. Profile view of a zoecium. Ordovician (Mohawkian), Black River (Decorah) shales, Cannon Falls, Minnesota. Fig. 18. ONCHOMETOPUS SIMPLEX Raymond and Narraway............... An imperfect specimen referred to the species on account of its general form but particularly on account of the absence of a concave border. Ordovician (Mohawkian), Nidulites bed of Chambersburg Is., Wilson, Maryland. Figs. 1-3 are after Weller; 4-6 are after Winchell and Schuchert; 7, 8, 12-17 after Ulrich. 397 216 219 213 212 348 CAMBRIAN AND ORDOVICIAN, PLATE XLVII MARYLAND GEOLOGICAL SURVEY 10 ALTOVA bahecob le Lt FOSSILS OF THE CHAMBERSBURG LIMESTONE (NIDULITES BED). PLATE XLVIII Figs. 1-7. PLECTAMBONITES PISUM Ruedemann.............sseeeeeeeeeee 1. A pedicle valve less tumid than usual. X 1.25. 2. Posterior view of same. 1.25. 3. Pedicle valve of normal dimensions. > 1.25. 4. Brachial valve of an entire shell. X 1.25. 5. Internal cast of pedicle valve showing casts of muscular and vas- cular impressions. X 1.25. . Interior view of brachial valve. X 1.25. 7. Pedicle valve with long cardinal line. X 1.25. Ordovician (Mohawkian), Rysedorph conglomerate, Ryse- dorph Hill, Rensselaer County, New York. a> Figs. 8-11. ParaSTROPHIA HEMIPLICATA Hall........... 02 cece ee eee eee eee 269 8,9. Brachial and pedicle views of an entire specimen. 10,11. Anterior and lateral views of the same. Ordovician (Mohawkian), Lower Trenton portion of the Jack- sonburg ls., near Newton, New Jersey. Fig. 12. ORBICULOIDEA LAMELLOSA (Hall)......... 2. ceca cece ence ee enee 234 Exterior of a brachial valve. X 2. Ordovician (Mohawkian), Trenton ls., Middleville, New York. Figs. 18-15. ARTHROPORA BIFURCATA UIrich...........ce cee e eee erence eens 224 13. Segment natural size. 14. Surface of upper part of original of Fig. 15 showing aged condition of zoecia. X 18. 15. A small segment natural size and its upper part X 18 illustrating the youthful condition. Ordovician (Mohawkian), Black River (Decorah) shales, St. Paul, Minnesota. Figs. 16-18. CHRISTIANIA TRENTONENSIS Ruedemann..................0- 256 16. Somewhat exfoliated pedicle valve. X 2. 17. Brachial valve. xX 2. 18. Interior of brachial valve showing the quadrupal adductor scar divided by high vertical muscular walls. X 2. Ordovician (Mohawkian), Rysedorph conglomerate, Ryse- dorph Hill, Rensselaer County, New York. Figs. 19, 20. ZyGosprra EXIGUA (Hall)........ 0... ee eee eee eee ene ene 273 Pedicle and brachial valves illustrating the smooth exterior. X 2. Ordovician (Mohawkian), Trenton ls., Watertown, New York. Fig. 21. CyRTOCERAS CAMURUM Hall....... ccc ccc cece eee rece neeee 330 Type specimen showing the rapidly curving shell. Ordovician (Mohawkian), Trenton ls., Middleville, New York. Fig. 22. ORTHOCERAS ARCUOLIRATUM Hall........... i bea lense ewan awl ge sie 323 Fragment of the shell, exhibiting the arched annulations. Ordovician (Mohawkian), Trenton ls., Watertown, New York. Figs. 23-25. ISoTELUS GIGAS DeKay........... ccc cece cece e eee eeenenee 344 23. A small but rather perfect specimen of the spinous form. 24. A larger example of same. 25. Aspinose form. Ordovician (Mohawkian), Trenton ls., near Trenton Falls, New York. Figs. 1-7, 16-18 are after Ruedemann; 8-11, 13-15 are after Ulrich; 12, 19, 20 are after Hall and Clarke; 21, 22 are after Hall. 398 CAMBRIAN AND ORDOVICIAN, PLATE XLVIII MARYLAND GEOLOGICAL SURVEY FOSSILS OF THE CHAMBERSBURG LIMESTONE (CHRISTIANIA AND GREENCASTLE BEDS) . 28 PLATE XLIX PAGE Fig. 1. SrroPHOMENA SCULPTURATA Bassler 1. SP........ 0c cece eee ee eeee Exterior of a brachial valve illustrating the highly ornamented sur- face. X 2. Ordovician (Mohawkian), Sinuites bed at base of Martinsburg shale, 1 mile south of St. Thomas, Pennsylvania. - Fig. 2. LEPraENA TENUISTRIATA Sowerby Var........ cece cece eee eeee seis Pedicle valve of an incomplete specimen. X 2. Ordovician (Mohawkian), Sinuites bed at base of Martins- burg shale, 1 mile south of St. Thomas, Pennsylvania. Figs. 3-10. CHRISTIANIA LAMELLOSA Bassler N. SP...... 0.0 e eee ee ee eee eens 3,4. Pedicle valve showing the characteristic lamellose markings. Natural size and X 2. 5,6. Another example showing pedicle valve, natural size and X 2. 7,8. Brachial valve of another specimen natural size and X 2. 9,10. Interior of a brachial valve illustrating characteristic muscular scars. Natural size and X 2. Ordovician (Mohawkian), base of Martinsburg shale, Stras- burg, Virginia. Figs. 11-138. TripLecia (CLIFTONIA) SIMULATRIX Bassler n. sp...........- 11. Pedicle valve of an exfoliated specimen. Ordovician (Mohawkian), Sinuites bed at base of Martins- burg shale, 1 mile south of St. Thomas, Pennsylvania. 12,18. Brachial valve with the shell preserved. Natural size and enlarged. Ordovician (Mohawkian), base of Martinsburg shale, Stras- burg, Virginia. Figs. 14-16. Lepropotus ? ovaLis Bassler n. SP.....-.. eee cece eee eee 14. Exterior of pedicle valve. xX 4. 15. Interior of brachial valve showing the median and lateral septa. x 4, 16. Interior of another brachial valve with markings more obscure. x 4. Ordovician (Mohawkian), Sinuites bed at base of Martinsburg shale, 2 miles northwest of Kauffman, Pennsylvania. Figs. 17-21. DALMANELLA EDSONI Bassler n. SP....... eee ee cece teen eens 17. Interior of brachial valve. 18. Pedicle valve of incomplete specimen illustrating the strongly marked ridges. 19. Brachial valve of specimen almost complete. Sinuites bed at base of Martinsburg shale 1 mile south of St. Thomas, Pennsylvania. 20. Brachial valve of partially exfoliated example. 21. Exfoliated and incomplete pedicle valve. Ordovician (Mohawkian), Trenton limestone, Shipyard Bay, Highgate Springs, Vermont. Figs. 22, 23. COLEOLUS IOWENSIS JaMeS........ cece eee ee eee eee tenes 22. Rock fragment with numerous specimens illustrating the long, slender curved form. X 2. 23. Portion of the same showing exterior of shells. X 6. Richmond group, Maquoketa shale, Graf, Iowa. 399 250 260 257 266 230 243 320 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE XLIX 22 BRACHIOPODA AND MOLLUSCA OF THE MARTINSBURG SHALE (SINUITES BED). PLATE L PAGB Figs. 1-5. CONOTRETA RUSTI (Walcott) ...... 0... ccc eee eee eee tens asa S284 Internal cast of pedicle valve showing impressions of the strong “apical callosity and the radiating ridges. x 8. . Apical view of the same. The subtriangular posterior slope and its obscurely defined median furrow are visible. xX 9. . Cardinal view of a young individual with very faint posterior slope. 12. Ordovician (Mohawkian). Trenton Is., Trenton Falls, New York. . Cardinal view of very small example retaining the shell. X 25. . Profile of the same. Ordovician (Mohawkian) Trenton ls., Covington, Kentucky. HES 6-8. LINGULA RICINIFORMIS (Hall)...... Mealy 2B aee eee RLY Role we sole ite ie 22 Well preserved ventral valve. ? Enlarged sketch of the posterior portion of the same specimen showing growth stages, p, protegulum ; 0, obolella; s, nealogic. Ordovician (Mohawkian) Trenton shale, St. Paul, Minnesota. 8. A nearly complete, partially exfoliated valve. X 2. Ordovician (Mohawkian) Trenton portion of Jacksonburg ls., Jackson- burg, New Jersey. Figs. 9, 10. DALMANELLA TESTUDINARIA (Dalman) Var........e cece eee rene nenee 242 9. A pedicle valve. X 2 10. Brachial valve. X 2. Ordovician (Mohawkian) Trenton portion of Jacksonburg Is., Jackson- burg, New Jersey. Figs. 11-13. HINDIA PARVA (Ulrich) ....... eee ee eee eee eee ee eee eee eee eas 197 11. Three specimens showing variations in size. 12. Vertical section. x 10. 18, Longitudinal section. X 10. Ordovician (Mohawkian) Trenton shales, Fillmore County, Minnesota. Figs. 14-16. ScENIDIUM ? MEROPE (Billings) ......... cee eee eee eee e eee 268 Ventral side, area, and lateral views of the type. Ordovician (Mohawkian) Trenton ls., Ottawa, Ontario. Figs. 17-18. CYRTOLITINA NITIDULA (Ulrich) ....... 22s cee eee etree eee teen gee 311 Two views of the type. The specimen, although a cast of the interior, preserves the surface markings. 2 Ordovician (Mohawkian) Trenton ls., Covington, Kentucky. Figs. 19, 20. EccyLIOMPHALUS TRENTONENSIS (Conrad) .....-.--seeeeeeeeee .. 806 Two views of an incomplete specimen. Ordovician (Mohawkian) Trenton portion of the Jacksonburg ls., Jacksonburg, New Jersey. Figs. 21, 22. MICROCERAS INORNATUM (Hall) ...........-. Aries tascaVa ne as asta Veeeaoeeeta Raipaas es . 812 Side and edge views of a complete shell. X 6. Ordovician (Cincinnatian) Maysville group, Cincinnati, Ohio. BIER: on 26. CYCLORA MINUTA (Hall) ............ FECES TED S-4 SRT HBlstnle hea 316 . View of side and aperture. X 6. Under side of shell. X 6. 35. Under side of another specimen showing lip more spreading near umbilicus. oh 0 be x 6. 26. View of side and aperture. X 6. Ordovician (Cincinnatian) Maysville group, Cincinnati, Ohio. Fig. 27. CyYCLORA HOFFMANNI (Miller) .............. 8:16 pA Repeats ng Bd Sue. colmlerastante on . 317 A complete shell. X10. Ordovician (Cincinna tian) Maysville group, Cincinnati, Ohio. Figs. 28-30. CycLora PARVULA (Hall) ...........-e00% oe GREED EAL SS ea eRA ES 316 28. View of side and aperture. X 8. 29. Under side of shell. x 8. 30. Side view of shell illustrating the characteristic angulated first whorl. xX 8. Ordovician (Cincinnatian) Maysville group, Cincinnati, Ohio. Figs. 31-36. STROPHOSTYLUS TEXTILIS (Ulrich and Scofield)...............0008 315 31. Cast of the interior showing the usual form of the species. 32. Surface markings of a well preserved specimen. X 5. 33. Cast of a depressed shell retaining traces of the external markings. 34. Ventral view of a testiferous example. 35. Shell in which part of the last whorl was removed to show the spirally- twisted plates of the columella. 36. Dorsal view of the incomplete shell. Ordovician (Mohawkian) Trenton sheles, St. Paul, Minnesota. Figs. 37-39. SINUITES CANCELLATUS (Hall) ....... 0. eee eee eee cece tence ne enee 313 Three views of an entire shell representing the average proportions of the Trenton form of the species. Ordovician (Mohawkian) Trenton shales, Chatfield, Minnesota. Figs. 40, 41 SINUITES GRANISTRIATUS (Ulrich) ...... 5a Animals aS Bn Roet) sascoden OD ora 314 40. Dorsal view of an average example. 7 41. View of aperture of another specimen. Ordovician (Cincinnatian) Eden shale, Covington, Kentucky. Fig. 42. CONULARIA TRENTONENSIS (Hall) .........00. earienadeieia-s sissies sahevavinnts éevars, B20 A nearly complete example. Ordovician (Mohawkian) Trenton portion of Jacksonburg ls., Jackson- burg, New Jersey. Fig. 43. TROCHOLITES AMMONIUS (Conrad) .... cece eee cece eer eeee Siege eb .. 327 Emmons’ illustration of this species. Ordovician (Mohawkian) Trenton ls., of New York. Figs. 1-5 are after Hall and Clarke; 8-10, 19, 20, 42 are after Weller; 6, 7, 11-13 are after Winchell and Schuchert ; 14-16 after Billings; 17, 18, '31- -41 after Ulrich and Scofield; 21-26 after Meek; and 23 after er 400 ATE L OVICIAN, PL CAMBRIAN AND ORD VEY OLOGICAL SUR MARYLAND GE ri ry St my Crt INUITES BED). THE MARTINSBURG SHALE (S FOSSILS OF PLATE LI PAGE Vise, 1-3. SPYROCPRAS BILINEATUM (Hall) ......... 0... cc ccc cere etna rene 825 Apical portion of shell showing gradual development of the annulations. X 2. 5 Fragment of small shell exhibiting surface markings. X Ordovician (Mohawkian) Black River (Decorah) Shales of Minnesota. 3. Portion of shell illustrating appearance when broken out of limestone. Ordovician (Mohawkian) Sinuites bed at base of Martinsburg shale, 1 mile south of St. Thomas, Pennsylvania. Figs. 4-7. ORTHOCERAS JUNCEUM (Hall) ..... cee cece eee een eer t cette eens 323 ‘4. Wragmentary shell showing convexity of septum and a section of the same illustrating the central portion of the siphuncle. 5. A shell with the outer chamber well preserved. Ordovician (Mohawkian) Trenton Is., Watertown, New York. 6. Another fragment with the outer chamber and a number of septa preserved. 7. Outer chamber of another example, natural size. Ordovician (Mohawkian) Sinuites bed at base of Martinsburg shale, 1 mile south of St. Thomas, Pennsylvania. Figs. 8-10. AMPHILICHAS TRENTONENSIS (Conrad) ...... e+e eee ce eer een are erae 354 8. Dorsal view of a nearly complete cranidium. 9, 10. Anterior and lateral views of the same. Ordovician (Mohawkian) Trenton portion of the Jacksonburg ls., Jacksonburg, New Jersey. Fig. 11. EOHARPES OTTAWAENSIS (Billings) 2.2.0.0... cece cece eee ete cence 332 Billings’ illustration of a nearly complete example of this fine species. Ordovician (Mohawkian) Trenton ls., Ottawa, Ontario. Figs. 12-14. CYPHASPIS MATUTINA (RuedemannD) ....... ce cere renee ence nee eeeee 353 12. Dorsal view of cranidium of young specimen. X 10. 13. Lateral view of same. X 10. 14. Cranidium of older example. X_5. Ordovician (Mohawkian) Rysedorph conglomerate, Rysedorph Hill, Rensselaer County, New York. Fig. 15;. CALYMENE SENARIA. (CONTA): o606634 644 Heaw ade oo he N TE RES ER EK EOE SSD 357 3 Posterior view of pygidium illustrating the usual part of the trilobite ound. Ordovician (Mohawkian) Trenton portion of Jacksonburg ls., Jackson- burg, New Jersey. Fig. 16. TRIARTHRUS FISCHERI (Billings) 1... 0... cece cece eee eee teen eee “341 Type specimen. A glabella with the fixed cheeks. Ordovician, Chazyan of Newfoundland. Figs. 17, 18. TRIARTHRUS BECKI (Green) ........ cee eee eee eee eee eee 342 > Two specimens of average size showing the characteristic tubercles along the median line of the axis. Ordovician (Cincinnatian) Utica shale of New York. Figs. 19, 20. CRYPTOLITHUS TESSELATUS (Green) ......... eee cece eee eet eee 335 Dorsal and anterior view of the head, the portion usually found. . Ordovician (Mohawkian) Trenton portion of Jacksonburg ls., Jackson- burg, New Jersey. Figs. 21-25. PROETUS LATIMARGINATUS (Weller) ........0- ccc cee eee cece ee eeees 352 1, 22. Dorsal and lateral views of nearly complete cranidium. X 2. 23. Dorsal view of same specimen. 4, 25. A complete free cheek. Natural size and X 2. Ordovician (Mohawkian) Trenton portion of Jacksonburg ls., Jackson- burg, New Jersey. Figs. 26-29. ILLAENUS AMERICANUS (Billings) 2... 0... cece eee ce eee eee eee 349 26, 27. Dorsal and front views of the original type. 28. Pygidium of the same. 29. A complete example. Ordovician (Mohawkian) Trenton ls., Ottawa, Ontario. Figs. 30-33. BUMASTUS TRENTONENSIS (Emmons) ........... ccc e eee ee eee eee 351 30. Cranidium of enrolled specimen with eyes preserved. 31. Pygidium of another enrolled example. 32. A complete although imperfect extended specimen showing the characteristic eight segments. ~- 33. Cephalon showing the lunate depressions. Ordovician (Mohawkian) Trenton ls., near Watertown, New York. Figs. 1, 2 are after Clarke ; 4, 5 after Hall; 8-10, 15, 19-25 after Weller; 11, 16, 26-29 after Billings: 12-14 after Ruedemann. 401 CAMBRIAN AND ORDOVICIAN, PLATE LI MARYLAND GEOLOGICAL SURVEY Hae ARIES Tcksdueds pote bek. Lad tots. A \ith AV. Dy aaa (0 1 KK y KN Ht ( A 29 MARTINSBURG SHALE (SINUIT ES BED). FOSSILS OF THE PLATE LII PAGE Figs. 1, 2. CoryNOIDES CALICULARIS Nicholson...........cee0eceee0e seeee 206 Nicholson’s figures of this small, interesting graptolite. Middle Ordovician of Great Britain. Figs. 3, 4. CLIMACOGRAPTUS SPINIFER (Ruedemann)...... she Bea aban ca law eee, 208 Two rhabdosomes. Ordovician (Cincinnatian), Utica shale of eastern New York. ‘J Figs. 5-7. CLIMACOGRAPTUS PUTILLUS (Hall)...... 2... cece csceceececues 202 Three examples enlarged showing the characteristics of the species. Ordovician (Cincinnatian), Utica shale of New York. Figs. 8, 9. SCHIZOCRANIA FILOSA (Hall)....... 0... cece eee e ete e eee eenee 235 8. Valve of Rafinesquina alternata with five pedicle valves of this species attached. One specimen shows the scars of the brachial valve. 9. Exterior of a brachial valve attached to Rajfinesquina. x 2. Ordovician (Cincinnatian), Maysville group, Cincinnati, Ohio. Figs. 10-12. CyciLornaA MINUTA Hall........... cece cece eee ee eee eeeee 316 Three views of this dwarfed gastropod. X 6. Ordovician (Cincinnatian), Maysville group, Cincinnati, Ohio. Fig. 18. LEpPToBOLUS INSIGNIS Hall............. 0. 0c eee eee eeee bagted toa areas 231 Exterior of the shell showing the concentric and radiating striae. x 8. Ordovician (Cincinnatian), Utica shale, Middleville, New York. Figs’ 14-16. ByTHocyPRIS CYLINDRICA (Hall).............c cece cece cnees 371 Side and two edge views of a complete carapace. X 20. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Fig. 17. CRYPTOLITHUS TESSELLATUS GIe€@N......... cece cece eee cece cence 335 Diagrammatic drawing of an entire specimen. ‘ Upper Ordovician of Canada. Figs. 18-20. TRIARTHRUS BECKI Gre@n......... cece cece cece ec ecccevaceece 342 Outline drawings of three specimens. Ordovician (Cincinnatian), Utica shale, New York. Figs. 21-23. CarYocARIS SILICULA Bassler n. Sp...........e0ee eee seeacaauatane 372 21. Valve of this crustacean, imperfect at one end. X 3. 22. A less complete example. X 3. 23. A specimen representing the opposite valve. X 3. Ordovician (Mohawkian), lower beds of Martinsburg shale, Strasburg, Virginia. Figs. 24, 25. LepmocoLeus JamMeEsi (Hall and Whitfield)............ Saieow olde Detached plates, enlarged. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Figs. 1, 2 are after Nicholson; 3-7 after Ruedemann; 8, 9, 24, 25 after Hall and Whitfield; 14-16 after Ulrich; and 13 after Hall and Clarke. 402 CAMBRIAN AND ORDOVICIAN, PLATE LII MARYLAND GEOLOGICAL SURVEY pcre SS FOSSILS OF THE MARTINSBURG SHALE (CORYNOIDES BED). PLATE LIII Fig. 1. CLIMACOGRAPTUS BICORNIS (Hall)......... 0. cece cece eee eeeees 204 Typical specimen showing sicular extremity. Ordovician (Crazyan), Normanskill shale, Kenwood, New York. Figs. 2-4. DIPLogRAPTUS VESPERTINUS Ruedemann...........-..0- eee eeee 205 2. Early form of the species. xX 5. 3. Late type. xX 5. 4. Enlargement of a larger specimen. xX 5. Ordovician (Chazyan), Normanskill shale, Van Schaick Island, New York. Pig. 5 “MBRGOGRINUS: SDs sepies sie ava xg hs ieee aecniesa aia. Gage Deeks Sind Seg Nw eee 211 Several segments. xX 4. Ordovician (Cincinnatian), Eden portion of Martinsburg shale, one and one-half miles northeast of Fort Loudon, Pennsyl- vania. Figs. 6, 7. HETEROCRINUS HETERODACTYLUS Hall............. cece eee eee 210 6, An example preserving the body and a part of the column. 7. Portion of the same enlarged. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Fig. 8.. HUDSONASTER CLARKI Bassler, N. SP... .. 2... cece eee cence eens 211 Photograph of a gutta-percha squeeze of the two type specimens pre- served as a mold in sandy shale. X 4. Ordovician (Cincinnatian), Eden portion of the Martinsburg shale, one and one-half miles northeast of Fort Loudon, Pennsyl- vania. Fig. 9. BERENICEA VESICULOSA Ulrich.......... BM sudrdtsaniideacd uain eu teuncece aan Goa 214 Surface of the type specimen. X 18. : , Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Fig. 10. HALLOPORA ONEALLI SIGILLARIOIDES (Nicholson)................ 222 A fragment of sandstone with several molds of this abundant species. Ordovician (Cincinnatian), Eden portion of the Martinsburg shale, one and one-half miles northeast of Fort Loudon, Pennsyl- vania. Figs. 11-183. BytTHopora ARcCTIPORA (Nicholson)................ cece eeeee 221 11,12. Fragment of the cylindrical zoarium, natural size and a portion enlarged. 13. Several zowecia much enlarged. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Figs. 14,15. ARTHROPORA CLEAVELANDI (JaMeS).........-ee cee eee eee eeee 225 14. Three segments. X 4. 15. Portion of a segment. X 18. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Figs. 1-4 are after Ruedemann; 6, 7, after Meek; and 11-15 after Nicholson. 403 CAMBRIAN AND ORDOVICIAN, PLATE LIII MARYLAND GEOLOGICAL SURVEY 5 5 a | pene an Ot oo Cad PUD RG SHALE (EDEN DIVISION). MARTINSBU FOSSILS OF THE PLATE LIV Figs. 1, 2. BaTostoMa JAMESI (Nicholson) .........eescceeceer cere er eenes .. 220 1. ‘Zoariun natural size. 2. Surface of same enlarged, showing rounded cells with thick wall and numerous acanthopores. Ordovician (Cincinnatian) Eden shale, Cincinnati, Ohio. Figs. 3, 4. RAFINESQUINA SQUAMULA (James) ..... a. d ood a 5s mole .. 264 Two examples, each showing the pedicle “valve. Ordovician (Cincinnatian) Eden shale, Cincinnati, Ohio. Figs. 5, 6. DALMANELLA MULTISECTA (Meek) 2... .- cere cece nec e ete erence eens ~. 244 5. Pedicle valve. 6. Interior of brachial valve. Ordovician (Cincinnatian) Eden shale, Cincinnati, Ohio. Figs. 7-9. STOPHOMENA HALIIE (Miller) .......... SIE Raub us dalariersasade-e ai sya gesrmya tpbneaset.s 251 7. Interior of pedicle valve. 8. Brachial valve. 9. Interior of brachial valve. Ordovician (Cincinnatian) Eden shale, Cincinnati, Ohio. Figs. 10-14. StTroPHOMENA SINUATA (James) ........... wy csieipie aoe A ha ate 252 10-11. Interior of the brachial and pedicle valves. 12-14. Anterior view and the two sides of a specimen. Ordovician (Cincinnatian) Maysville group, Cincinnati, Ohio. Figs. 15, 16. PLECTORTHIS PLICATELLA (Hall) ..... 0. cece eee cect reece ee eeee 242 Brachial valve and interior of the same valve of ‘another example. Ordovician (Cincinnatian) Maysville group, Cincinnati, Ohio. Figs. 17-19. CTENODONTA OBLIQUA (Hall) 2... ... cee eee eee eee eee eee eee . 278 Views of two shells and the cardinal side of one. X 10. Ordovician (Cincinnatian) Maysville group, Cincinnati, Ohio. Figs. 20-22. ZYGOSPIRA MODESTA (Hall) ....... cc eee cece ee eee et eee een enee 274 Opposite sides and edge view of this small brachiopod. Ordovician (Cincinnatian) Maysville group, Cincinnati, Ohio. Figs. 23, 24. _PHOLIDOPS CINCINNATIENSIS (Hall) ...... da batten aetna ita wee. 236 Brachial valve and profile of the same. X 3 Ordovician (Cincinnatian) Maysville group, Cincinnati, Ohio. Fig. 25. LEpPrAENA GIBBOSA (JAMES) 2.2... eee cee rete eee enter eee eens 259 Pedicle valve of a specimen identified by the author of the species. Ordovician (Cincinnatian) Eden shale, Cincinnati, Ohio. Figs, 26-29. CTENODONTA FILISTRIATA (Ulrich)...... BEET elase DE PEE Wa eS MENS . 279 26. Left valve. 27. Right side of cast of interior. 28. Cardinal view of left valve. 29. Portion of surface of shell, highly magnified. Ordovician (Cincinnatian) Eden shale, Cincinnati, Ohio. Fig. 30. LyRODESMA CONRADI (Ulrich) ........ ese eee eee eee eens 286 gone of the interior showing the muscular scars and the sinuate ‘pallial "Gndnwielan (Cincinnatian) Eden shale, Cincinnati, Ohio. Figs. 31-83. _PLECTAMEBONITES RUGOSUS (Meek) .......0..0eeee0% Sisveea goweece Loo 31, 32. Pedicle and brachial valves. 33. Interior of the brachial valve. Ordovician (Cincinnatian) Eden shale, Cincinnati, Ohio. Figs. 34-36. BySSONYCHIA VERA (Ulrich) ......- cee eee ce reece eee ooaseeets: 282 34, 35. Left side and anterior view of a partial cast of the interior. 36. Well preserved cast of the interior showing muscular impressions. Ordovician (Cincinnatian) Eden shale, Newport, Kentucky. Fig. 37. CLIDOPHORUS PLANULATUS (Conrad) ........+s22e005 6rd Cee MO CIDE US LO Shell of this species on slab with Plectambonites. Ordovician (Cincinnatian) pe shales of New York. Figs. 1, 2 are after Nicholson ; 5, 6, 10-24 after Meek ; 7- 9 after Miller; : and 26-30, 34 after Ulrich. 404 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE LIV FOSSILS OF THE MARTINSBURG SHALE (EDEN DIVISION ) ‘ PLATE LV Figs. 1-4. LepmocoLteus Jamesi (Hall and Whitfield)................05 371 1. Sketch showing the plates in position. 2,38. Detached plates enlarged. . Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. 4. A broader plate referred to this species. X 10. Ordovician (Mohawkian), Trenton ls., Trenton Falls, New York. Figs. 5,6. LopwosprrA (RUEDEMANNIA) LIRATA Ulrich.............0..065 395 5. A specimen with numerous spiral ridges on the basal part of the volutions. 6. Portion of the lower part of the last whorl of same including the band. X 3. Ordovician (Cincinnatian), Eden shale, Newport, Kentucky. Figs. 7, 8. HORMOTOMA GRACILIS (Hall).......... 00. cece ence eter ee eees 292 View natural size, and a portion enlarged, of the typical form of this species. Richmond (Maquoketa) shale, Graf, Iowa. Figs. 9-11. SINUITES GRANISTRIATUS (Ulrich)........... 0.0. cece eee ences O14 9. Lateral view of a specimen. 10. Dorsal view of an average example. 11. Apertural view showing form of mouth and extent of the gran- ostriate expansion. Ordovician (Cincinnatian), Eden shale, Covington, Kentucky. Figs. 12-21. SmnvITEs CANCELLATUS (Hall)........ 0... cece cece eee eens 313 12,13. Two views of a cast of the interior showing strong wrinkles of growth near the aperture. 14. Apertural view of shell with mouth less expanded than usual. 15.16. Two views of a small cast. Ordovician (Mohawkian), Black River and Trenton forma- tions of Minnesota. 17. Dorsal view of a globose variety. 18. Surface of left lobe of outer lip. X 4.5. Ordovician (Cincinnatian), Eden shale, Covington, Kentucky. 19-21. Three views of an average entire shell. Ordovician (Mohawkian), Trenton shales, Chatfield, Minne- sota. Figs. 22-24. TETRANOTA OBSOLETA UIrich............ 00sec ee eee e ee eteee 310 Three views of the type. Ordovician (Mohawkian), Trenton shale, Goodhue County, Minnesota. Figs. 25, 26. Liosprra MICULA (Hall)........... 00.00 ccc ccc eee ee ueeeeees 296 Two views of a nearly perfect example. Ordovician (Cincinnatian), Eden shale, Covington, Kentucky. Fig. 27. OrRTHOCERAS TRANSVERSUM Miller. .......0.-.c0cccecccccsececces 324 Type specimen, showing the transverse surface markings. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Figs. 28-31. ByTHOCPRIS CYLINDRICA (Hall)........ 0... cc ccc cccccecceuue 371 28, 30, 31. Views of a complete carapace. X 20. 29. Interior of a right valve. x 20. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Fig. 32. ULRICHIA BIVERTEX (Ulrich)............0.cc cc cece cece ee nneeees 370 Right valve showing the two prominent nodes. X 20. Ordovician (Mohawkian), Trenton shales, Montgomery County, New York. Fig. 33. APARCHITES MINUTISSIMUS (Hall).............cceceecccecceucs 366 Valve highly magnified. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Fig. 34. CERATOPSIS CHAMBERSI (Miller)...........0. 0... cc ccc ccc eccuce 369 Valve illustrating the prominent spine. Highly magnified. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Figs. 1-3, 33, 34, are after Hall and Whitfield; 6, 32 after Ruedemann; 4-26 after Ulrich and Scofield; 27 after Miller; and 28-31 after Ulrich. 405 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE LV FOSSILS OF THE MARTINSBURG SHALE (EDEN: DIVISION). PLATE LVI PAGE Figs. 1, 2. CALYMENE GRANULOSA Foerste.......... cece cece cece ween eaee 356 1. An entire, extended specimen. 2. Portion of same showing granulose surface. X 4. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Figs. 3, 4. ISoOTELUS STEGOPS GTee@N...........ece eee eens peinislg Sete gh is gts 342 3. A complete although somewhat imperfect example. — 4. The spinose form of the species. Ordovician (Cincinnatian), Eden shale, Cincinnati, Ohio. Figs. 5, 6. CRYPTOLITHUS BELLULUS (Ulrich) ...........0ccccececeeecaces 333 5. Cephalon with spines preserved. 6. The original type representing the young form of the species. x 3. Ordovician (Cincinnatian), Eden shale, Covington, Kentucky. Figs. 7-18. TRIaARTHUS BECKI GYeE@N........... cece eee cece eee ee ee eeaee 342 7-11. Specimens in various stages of growth. 12,18. Drawings of Beecher’s celebrated restorations showing the appendages in position. Ordovician (Cincinnatian), Utica shale, New York. Figs. 14-17. CryproLiTHUS RECURVUS (Ulrich) n. sp.............0. cee eee 334 14, 15. Two imperfect but almost entire specimens. Ordovician (Cincinnatian), Eden shale, Covington, Kentucky. 16. Cephalon showing convexity. 17. Pygidium. Ordovician (Mohawkian), Trenton ls., Covington, Kentucky. Fig. 18. CoRNULITES FLEXUOSUS Hall.......... 0... ccc ccc eee eeceetcceeee 276 A group of tubes adhering to a brachiopod shell. Ordovician (Cincinnatian), Maysville group, Cincinnati, Ohio. 406 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE LVI FOSSILS OF THE MARTINSBURG SHALE (EDEN DIVISION ). PLATE LVII Figs. 1-3. LINGULA NICKLESI Bassler N. SP......-.. cece cece eee cece eneees 1,2. Two examples, one partly exfoliated. 38. View of specimen shown in Fig. 1. X 4. Ordovician (Cincinnatian), Maysville group, Fairview forma- tion, Cincinnati, Ohio. Figs. 4-7. PLECTORTHIS PLICATELLA (Hall).......... 0.0 cece cece ce eeeeee 4,5. Front and interior. 6, 7. Cardinal and profile views of shell. Ordovician (Cincinnatian), Maysville group, Fairview forma- tion, Cincinnati, Ohio. Fig. 8. RAFINESQUINA ALTERNATA (Emmons)..........-..0eceeeeeceeues Pedicle valve of the usual Maysville form of the species. Ordovician (Cincinnatian), Maysville group, Cincinnati, Ohio. Figs. 9-12. OrTHORHYNCHULA LINNEYI (JaMeS)........... 2c cece ee eeees 9,10. Dorsal and ventral views of an average specimen. 11. Central portion of cardinal region showing distinct cardinal area and open delthyrium. X 3. 12. Profile views of shell natural size. p Ordovician (Cincinnatian), Maysville group, Nashville, Ten- nessee. Figs. 13-16. ZyGospIRA MODESTA Hall............. cece cece ee rec eeee oem Dorsal, ventral, edge, and side views cf an example of this abundant brachiopod. Ordovician (Cincinnatian), Maysville group, Cincinnati, Ohio. Figs. 17-28. ZyGoOsSprra ERRATICA Hall.............. Pe Sapetoue des ancatias sea evadep eashosuasine 17. A small example. 18. Profile view of moderately convex specimen. 19. Front view of another specimen. ~ 20, 21. Opposite sides of cast of a large example. 22. Cardinal view of large specimen. Ordovician (Cincinnatian), Pulaski shales of New York. Fig. 24. PreriInEA DEMISA (Conrad)............cc cece cue cecceeeeecees Left valve, natural size. Ordovician (Cincinnatian), Maysville group, Cincinnati, Ohio. Fig. 25. MopioLODON TRUNCATUS (Hall) ......... 0.0. c cece cee cence eeeees Left side of a cast of the interior, showing usual aspect of the species. Ordovician (Cincinnatian), Maysville group, McMillan for- mation, Cincinnati, Ohio. Fig. 26. BySSoONYCHIA RADIATA (Hall)...... 0.0.0.0... ccee cece cceeeceenecs Left valve of the usual size. Ordovician (Cincinnatian), Maysville group, Fairview for- mation, Cincinnati, Ohio. Fig. 27. ALLONYCHIA OVATA Ulrich.......... 0.0. cc cc cece eeeeeneceunees Left valve, natural size. Ordovician (Cincinnatian), Maysville group, Fairview forma- tion, Covington, Kentucky. ss Figs. 28, 29. BySSONYCHIA PRAECURSA Ulrich............. ccc cceeecceeees 28. Cast of interior of right valve. 29. Anterior view of shell showing the byssal opening. Ordovician (Cincinnatian), Lorraine shales, Lorraine, New York. Figs. 4-8, 13-16 after Meek; 17-23 after Hall; 9-12 after Hall and Clarke; 24, 26 after Hall and Whitfield; and 25, 27-29 after Ulrich. 407 241 265. 271 274 284 288 282 284 283 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE LVI} FOSSILS OF THE MARTINSBURG SHALE ( MAYSVILLE DIVISION ). PLATE LVIII PAGE Fig. 1. ORTHODESMA NASUTUM Conrad............. cece eet 289 A fairly well preserved right valve showing the narrow, extended, nasute form. Ordovician (Cincinnatian), Orthorhynchula bed at top of Fairview formation, Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Pennsylvania. Figs. 2, 3. ISCHYRODONTA UNIONOIDES (Meek).......cee eee eee rereeeees 281 2. Right valve of an example presenting the test. 3. Impressions of inner side of a right valve showing the anterior muscular scar. Ordovician (Cincinnatian), top of Fairview or base of McMillan formation, Covington, Kentucky. . Fig. 4. RAFINESQUINA SQUAMULA (JaM€S)....... 0c cece cece eee tenes 264 Impression of the shell in sandstone. Ordovician (Cincinnatian), Orthorhynchula bed at top of Fairview formation, Tuscarora Mountain, one and one-half miles southeast of McConnellsburg, Pennsylvania. Figs. 5, 6. ORTHOCERAS LAMELLOSUM Hall............. eee e cece cece cece 324 5. View showing separation of septa and other characters of the shell. 6. View illustrating position of the siphuncle. Ordovician (Cincinnatian), Pulaski shales near Pulaski, New York. Figs. 7-9. LiIoSPIRA MICULA (Hall)........ 0... cece cece eee eee eee enone 296 Top, bottom, and side views of a nearly perfect example. Ordovician (Cincinnatian), Eden shale, Covington, Kentucky. Figs. 10, 11. Isorerus MEGIsTOS Locke.............00.eeeeeeee pbk aiibiegr Grace 343 10. Meek’s type of Asaphus megistos Locke (Pal. Ohio, Vol. 1, pl. 14, fig. 13) enlarged one-third, representing the spinous form (? male). Ordovician (Cincinnatian), near top of Fairview formation, Cincinnati, Ohio. 11. Hypostoma of a larger example. Ordovician (Cincinnatian), lower part of McMillan forma- tion, Morrow, Ohio. Fig. 12. MopIoLOPSIS MODIOLARIS (Conrad) ........... ccc cee ceeeceeeene 286 One of Hall’s original figures which well represents the usual aspect of the species. It illustrates a slightly compressed right valve. Ordovician (Cincinnatian), Pulaski shales near Pulaski, New York. Figs. 2, 3, 7-9 are after Ulrich and 5, 6, 12 after Hall. 408 MARYLAND GEOLOGICAL SURVEY CAMBRIAN AND ORDOVICIAN, PLATE LVIII ee MEd FOSSILS OF THE MARTINSBURG SHALE (MAYSVILLE DIVISION), GENERAL INDEX A Abbe, Cleveland, Jr., 42. Acadian fossils, 89. Adirondack uplift, 74. Aikin, W. BE. A., 35. Alabama, 23, 83, 118, 136. Ale, Myra, 8. Alexander, J. H., 35, Algexe, Calcareous, 82. Proterozoic forms of, 85. Alleghany Plateau, 23. Amsterdam, N. Y., fossils from, 192. Antietam battle-field, 70, 80. Antietam Creek, 57. Antietam sandstone, 48, 54, 57, 58, 59, 65, 88, 89. Composition of, 58. Antietam Station, 85. Appalachian Region, 23, 60, 88. Appalachian Valley, 60, 61, 67, 76, 83, 85, 89, 90, 101, 106, 107, 109, 110, 114, 116, 118, 126, 129, 132, 154, 156, 160, 161, 167, 191. Fossils from, 190, 196, 201, 202, 206, 208, 241, 245, 257, 292, 300, 308, 315, 360. Axeman limestone, 101. Bain, H. F., 87. Bassler, R. S., 11, 13, 23, 42, 48, 185, 187. Bear Pond Mountain, 172. Beaver Creek, 65, 70. Beekmantown formation, 103, 117, 140. Beekmantown limestone, 48, 76, 80, 82, 87, 89, 114, 115, 116, 123. Areal distribution. 109. Faunal zones, 96. Generalized section of, 93. Lithologic character of, 92. Residual products of, 105. Section of, 94. Topography of, 105. BeekmantowmConococheague boundary, 103. Bellefonte, Pa., Fossils from, 347. Bellefonte dolomite. 101. Benevola, 65, 70. Berry, E. W., 7. 29 Billings, E., 196, 308, 341. cited, 309, 319, 333, 337, 350. Birdseye limestone, 27. Bissel, 99. Black River, 117, 129, 136, 141, 154. Black River group, Fossils from, 195, 199, 202, 213, 219, 226, 227, 249, 263, 273, 315, 326, 330, 349, 359. Blue Ridge, 61, 65, 67, 90, 132. Fossils from, 277. Blue Ridge District, 23. Blue Ridge Province, 56, 58. Blue Springs, Fossils from, 193, 198, 208, 209, 224, 226, 227, 238, 239, 240, 258, 261, 271. Boonsboro, 59, 65. Bostetter, 123. Bowman's Mill, 81. Brachiopods, 71, 82, 83, 97, 99, 100, 113, 135, 142. Braddock, 114. Brown, T. C., 44, 87. Buena Vista shale, 67. Burnside Bridge. 70. Butts, Charles, 88. Cc Caleareous alge, 82. Cambria, Wales, 25. Cambrian, 23, 25. Columnar sections of, 48, 49. Correlation table of, 51. Geology of, 24. History of, 25. Paleogeography of, 45. Paleontologic characteristic of, 50. Physiography of, 23. Stratigraphic characteristics of, 50. Cambrian age, Fossils of, 88. Cambrian-Ordovician limestones, 60. Table of, 60. Thickness of, 60. Campbell, H. D., 67. Canada, 23, 1386. Fossils from, 202, 224, 231, 232, 238, 239, 248, 269, 277, 278, 282, 283, 285, 298, 302, 309, 326, 350, 359. Canadian system, 30, 31. Canajoharie, N. Y., Fossils from, 192, 303, 304. 410 GENERAL INDEX Canu, Ferdinand, 45, Caradoc Group, 25. Carlisle, Pa., 120. Fossils from, 306, 355. Caryocystites bed, 133, 136, 148, 149, 150, 151, 152, 154, Fauna of, 135. “ Cauliflower ’’ chert, 117. Catoctin Mountain, 53, 56, 58, 59, 110, 11, i332, Catoctin schist, 54. Cavetown, 61, 62, 70. Cearfoss, 147. Central Basin, Tennessee, 127. Cephalopods, 98, 99, 113, 115, 144. Ceratopea zone, 93, 96, 103. Fossils of, 104. Chambersburg, Pa., 94, 120, 124, 130, 131, 140, 143, 144, 153. Fossils from, 166, 197, 203, 206, 215, 231, 232, 235, 238, 239, 243, 269, 295, 306, 310, 312, 315, 316, 317, 320, 321, 323, 326, 327, 333, 836, 338, 341, 342, 350, 351, 353, 354, 355, 356, 357, 362, 373. Section 1 mi. east of, 94. Chambersburg limestone, 49, 117, 129, 145, 146, 147, 148, 149, 150, 151, 152, 153, 157. Age of, 153, Areal distribution of, 132. Correlation of, 153. Distribution of beds of, 152. Divisions of, 154. Faunal zones of, 132, Lithologic character of, 130. Sections of, 144. Thickness of, 131. Chambersburg quadrangle, 57. Fauna of, 164. Chambersburg-Gettysburg Pike, 94. Champlain Region, 120. Champlain Valley, 87, 90. Faunas of, 127. Charlton, 80, 86, 102, 103. Fossils from, 302. Chazy formation, 112. Chazyan age, 115, 117, 129. Chazyan limestones, 27, 120. Chazyan shales, Fossils from, 206. Chewsville, 65, 70, 73, 81, 82, 85. Christiania bed, 133, 140, 142, 143, 144, 145, 146, 147, 152,153. Fauna of, 143. Christiania zone, 144. Cincinnati, Ohio, Fossils from, 242, 251, 280, 282, 286, 324, 356. Cincinnatian series, 30, 156. Clark, William Bullock, 19, 41, 42, 212. Clarke, J. M., 170, 272. Cleland, H. F., 303. Clinton formation, 170. Coastal Plain, 23. Collingwood shale, 267. Colorado, Fossils from, 238. Columbia, Fossils from, 247. Conococheague Creek, 76, 132, 139, 141, 150, 151, 156, 158, 161, 217. Conococheague limestone, 48, 65, 72, 73, 74, 88, 89, 90, 92, 98, 106, 110. Age of, 82. Areal distribution of, 81. Correlation of, 82. Cryptozoon reefs of, 838. Edgewise conglomerate of, 86. Fossils of, 88. General section of, 78. Section of, 77. Topography of, 81. Contents, 11. ; Coplay limestone, 100. Corynoides bed, 158. Fauna of, 167. Cowans Gap, 168. Fossils from, 169, 221, 222, 237, 296, 811, 334, 356. Covington, Ky., Fossils from, 284, 312, 834, 335. Crown Point limestone, 120, 126. Cumberland Valley, 24, 76, 129, 191. Cumberland Valley Railroad, 108, 123, 360. Cushing, H. P., 74. Crinoid plates, 143. Cryptozoon reefs, 78, 83. Cryptozoon steeli zone, 93, 96, 101, 103, 107, 191, Fossils of, 102. D Dana, James D., 38, 45. Decorah shales, 139, 141. Fossils from, 197, 217, 224, 258. Dickey, Pa., Section N. W. of, 148, 149. Distribution of fauna, Tables of, 174. Dorsey, C. W., 41. Ducatel, J. T., 35, 36. E Eakles Mills, 59, 65. Fossils from, 234, 277, 319, 339. Eaton, H. N., 44. Echinospherites bed, 132, 133, 139, 144, 145, 146, 150, 151, 152, 153, 154. Fauna of, 189. Eden age, 156, 163. Eden division, 157, 158. Fossils of, 167, 169. GENERAL INDEX Eden formation, Fossils of, 169. Eden shale, Fossils from, 211, 214, 255, 260, 324, 334, 356. Edgewise conglomerate, 86. Elbrook formation, 48, 63, 65, 70, 72, 80, 81, Age of, 74. Areal distribution of, 72. Correlation of, 74. Lithologic character of, 72. Residual products of, 73. Thickness of, 72. Topographic form of, 73. Elbrook limestone, 76, 83, 88, 89. Elk Ridge, 53, 56, 58, 59. Emmons, §. F., 27. Eopaleozoic, 30. Esthonia, Russia, Fossils from, 218, 228. Etheridge, Robert, 45. F Fairview formation, 171, 272. Fairview Mountain, 172. Fossils from, 225, 275, 371. Foerste, A. F., 255, 265, 280, 285, 287. Fontaine, W. M., 37. Fort Cassin, Fossils from, 327, 332. Fort Hunter, Fossils from, 247, 304, 306, 362. Fort Loudon, 148, 149, 160, 168. Fossils from, 193, 197, 198, 199, 201, 202, 205, 208, 209, 210, 211, 212, 214, 221, 222, 225, 226, 227, 228, 237, 238, 239, 240, 242, 245, 251, 253, 255, 258, 260, 261, 265, 271, 273, 276, 278, 279, 280, 286, 292, 297, 300, 301, 309, 311, 315, 8324, 328, 334, 335, 342, 343, 356, 359, 865, 366, 367, 368, 369, 370, Section 4% mi. south of, 150. “ Fossiliferous graywacke series,” 25. Frazer, Persifor, Jr., 37, 38, 39. Frederick, 114, 115, 116. Fossils from, 209, 250, 322, 345, 356. Frederick limestone, 115. Age of, 117. Fossils of, 116. Thickness of, 116. Frederick Valley, 24, 90, 109, 110, 111, 113, 114, 115, 116. Frederick Valley limestones, 111. Age of, 113. Description of, 111. Extent of, 111. Structure of, 113. Fruitville, 66. Fucoids, 99. 411 Funkstown, 97, Fossils from, 190, 238, 247, 303, 304, 306, 807, 329, 330, 332, 348, 352. G Gatesburg dolomite, 83. Gastropods, 94, 98, 99, 100, 103, 104, 122, 128, 137, 163, Geiger, H. R., 32, 39. Goodnow, Frank J., 5. Grabau, A. W., 87. Grasty, J. S., 43. Great Valley, 24, 32, 73, 76, 81, 172. Elevation of, 24. Extent of, 24. Greater Appalachian Valley, 23. Division of, 23. Greencastle, Pa., 120. Fossils from, 224, 274, 328, 330, Section at, 147. Greencastle bed, 133, 140, 141, 143, 144, 145, 146, 147, 152, 153, 154. H Hagerstown, 62, 73, 81, 82, 85, 98, 99, 103, 107, 110, 126. Fossils from, 191, 192, 196, 200, 246, 247, 267, 291, 297, 299, 303, 304, 305, 306, 307, 322, 340, 346, 347, 348, 362, 363. Hagerstown Valley, 24, 57, 65, 73, 80. ~ General section of Conococheague limestone in, 78. Hagerstown-Frederick trolley road, 64. Halfway, 103. Fossils from, 246, 290, 292, 300, 341, 360. Hall, James, 202, 323, 325. Cited, 189, 199, 201, 210, 242, 266, 272, 274, 275, 276, 283, 285, 288, 298, 317, 323, 327, 339, 342, 367, 870, 371, 372. Harmony Hill School, 65. Harper’s Ferry, 54, 57, 58. Harpers schist, 88. Harpers shale, 48, 54, 57, 58, 59, 61, 65, 89, 113, 114. Outcrop of, 58. Thickness of, 57. Harrington, Emerson C., 5, 9. Harrisburg, Pa., 120. Hayes, C. W., 117. Highbridge, Ky., 118. Highgate Springs, Fossils from, 244. Historical Review, 25. Hitchcock, E., 36. Hoosac Mountains, 27. Hoyt limestone, 74. Fossils from, 190, 191. 412 Hudson River formation, 112. Hudson River shale, 27, 113. Hunt, T. Sterry, 37, 45. Huyett, 105. Fossils from, 291, 293, 294, 299, 302, 327, 331, 364. Illinois, Fossils from, 320. Illustrations, 15. Introduction, 23. Iowa, Fossils from, 268, 320. J James, U. P., cited, 260. Jandorf, M. L., 44. Jefferson, Thomas, 34. Jordan Knob, Pa., 168. Fossils from, 169, 205, 210, 211, 212, 214, 221, 222, 225, 237, 242, 245, 251, 253, 255, 260, 265, 276, 279, 280, 286, 296, 297, 311, 315, 324, 834, 335, 348, 356, 367, 370, 372. Juniata formation, 49, 156, 157, 168, 170. Juniata shales, 161. K Kauffman, Pa., 123, 139. Fossils from, 231. Keedysville, 58, 60. Keith, Arthur, 32, 34, 39, 40, 57, 59, 67. Kentucky, 315, 327. Fossils from, 195, 197, 224, 230, 272, 300, 301, 309, 315, 327. Kentucky River, 118. Keyes, C. R., 34, 39, 112, 113, Cited, 111. Kittatinny limestone, 76, 99. Fossils from, 100, 346. Kuckers shales, Fossils from, 228. L Lake Champlain area, Fossils of, 261, 271, 310. Lapparent, A. de, 27. Lapworth, Charles, 26, 27. Le Gore, 111. Exposures at, 115, 116. Lebanon limestone, 118. Fossils from, 229. Lehigh Valley, 76, 120. Leitersburg, 82, 86. Lenoir limestone, 118, 120, 126, 129, 261. Lesley, J. P., 38, 40. Licking Creek, Pa., Section of, 95. GENERAL INDEX Little Antietam Creek, 66, Fossils from, 234. Little Falls dolomite, 74. Llandovery Group, 25. Lorraine, N. Y., Fossils from, 289, Loudon formation, 48, 53, 54, 88. Conglomerates of, 54. Thickness of, 53. Loudon slate, 54. Lower Cincinnatian shales, 167. Lower Martinsburg shale, Fauna of, 165. Lower Maysville, 156, 157, 160, 161, 170, 171. Lower Medina, 171. Lower Ozarkian, 83. Lower Stones River, 122. Fauna of, 122. Thickness of, 123. Lower Trenton, 156. Fossils from, 216. Lowville age, 133. Lowville limestone, 136, 151, 153. Ludlow, 26. M McConnellsburg, 160, 169, 172. Fossils from, 221, 222, 225, 237, 242, 251, 253, 265, 266, 272, 275, 276, 282, 283, 284, 285, 287, 288, 289, 290, 296, 311, 325, 334, 356, 372. Macfarlane, J. R., 39. Maclure, William, 35. Maclurea limestone, 298. McMillan formation, 161, 171. McMullen, H. A., 5. * Mapleville, 59. Maquoketa shale, 320. Marcou, Jules, 36. Marion, Fossils from, 202, 273. Section at, 145, 146. Martinsburg, W. Va., 122, 123, 133, 140, 154, Martinsburg shale, 49, 110, 129, 130, 142, 148, 145, 146, 147, 148, 149, 150, 151, 154, 157, 160, 161, 171. Areal distribution of, 161. Faunas of, 163, 164. Lithologic character or, 157. Section of, 157. Topographic features of, 161. Martinsburg shale belt, 77, 89, 94,. 103. 106, 191. Section east of, 144. Massanutten Mountain, 154. Massanutten syncline, 80, 81, 180, 154, 156, 158, 160, 161, 165. Mathews, FE. B., 7, 9, 43. GENERAL Maugansville, 128. Fossils from, 238, 247. Mayhill sandstone, 26. Maysville age, 163. Maysville division, Fossils of, 168, 170. Meek, F. B., cited, 236, 253, 275, 279. Mercersburg, Pa., 147. Fossils of, 166. Section 2% mi. S. E. of, 151. Mercersburg Quadrangle, Fauna of, 165. Middle Chazy limestone, 126. Middle Chazyan, Fossils from, 328. Middle Chazyan faunas, 127. Middle Cincinnatian division, 168. Middle Ozarkian formation, 83. Middle Stones River, 124, 126. Fauna of, 124. Middleville, Fossils from, 234, 330. Miller, 8. A., cited, 245, 251, 324. Millers Chapel, 86. Mingan Islands, Fossils from, 196. Minnesota, Fossils from, 197, 216, 217, 218, 224, 228, 230, 232, 249, 258, 268, 315, 333, 349. Mississippi River, 136. Mississippi Valley, 139. Fossils from, 203, 219, 241, 248, 263, 273, 278. Mitchill, S. L., 35. Mohawk Valley, Fossils from, 303, 304. Mohawkian age, 117, Mohawkian rocks, Fossils from, 198. Mohawkian series, 156. Montalto Mountain, Pa., 57. Montalta quartzite member, 57. Thickness of, 57. Moore, E. S., 44. Mosheim limestone, 118. Murchison, Sir R. I., cited, 25, 26. Murfreesboro limestone, 118, 120. N Narraway, J. E., 351. Cited, 348. Nason, F. 8., 87. National Highway, 97, 330, 363. Exposure along, 105. New Brunswick, Fossils from, 246. New Jersey, 76, 99, 120. Fossils from, 100, 195, 197, 232, 234, 246, 268, 270, 306, 307, 346, 351, 353. New Mexico, Fossils from, 238. New York, 90, 99, 118, 120, 126, 171. Fossils from, 100, 191, 202, 231, 234, 238, 239, 248, 254, 257, 273, 277, 278, 281, 282, 284, 291, 306, 307, 321, 323, 325, 327, 328, 329, 333, 346, 354, 232, 270, 285, 326, 359. INDEX 413 Newfoundland, Fossils from, 246, 294, 297, 299, 341, Nicholson, Dr., cited, 193. Nidulites bed, 132, 133, 140. 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154. Fauna of, 141. Nittanny dolomite, 101. Nittanny Valley, 101. Norfolk and Western Railroad, 85, 190. Normanskill, Fossils from, 206. North Mountain, 73, 110, 133, 147, 156, 163. Oo Observatory Hill, 60. Ohio, 67. Fossils from, 233, 281. Ohio Valley, 160, 161. Fossils from, 202, 203, 211, 214, 215, 221, 222, 231, 237, 248, 253, 255, 260, 272, 273, 278, 282, 283, 284, 285, 312, 315. Oneida conglomerate, 170. Ontario, 90. Fossils from, 234, 333. Odlites, 78, 86, 93. Orbigny, Alcide d’, cited, 26. Ordovician, 23, 26. Columnar sections of, 48, 49. Correlation table of, 50. Geology of, 24. History of, 25, Paleogeography of, 45. Paleontologic characteristics of, 50. Physiography of, 23. Stratigraphic characteristics of, 50. Orthorhynchula bed, 160, 168, 272. Fossils of, 170. Oswegan series, 170. Oswego sandstone, 161, 170, 171, 282. Ozarkian, 88, 89. Ozarkian fossils, 89. Ozarkian limestone, Fossils from, 190. Ozarkian system, 30, 31. Pp Paleogeography, Cambrian, 45. Ordovician, 45. Paleozoic rocks, Classification of, 30. . Parr’s Ridge, 24. ‘i Peabody, Charles, 43. ue * Peach lands,” 67. ‘ Pen Mar, Pa., 57, 58. oe RY 4.14 GENERAL INDEX Pennsylvania, 24, 60, 62, 66, 67, 68, 70, 73, 83, 96, 99, 101, 118, 120, 129, 132, 133, 142, 143, 144, 153, 156, 158, 160, 163, 167, 168, 171, 172. Fossils from, 190, 194, 195, 204, 210, 211, 217, 219, 224, 225, 230, 231, 234, 246, 249, 254, 257, 260, 264, 207, 270, 272, 274, ZTT, 282, 290, 292, 298, 319, 337, 344, 345, 349, 870, 371. Piedmont Plateau, 23, 24, 111. Division of, 24. Pierce limestone, 118. Pinesburg Station, 122, 126, 128, 132, 139, 144, 151, 156, 158, 161, 167. Fossils from, 194, 195, 201, 208, 216, 218, 219, 229, 230, 240, 241, 248, 249, 268, 264, 268, 298, 337, 365. Pinesburg-Wilson area, 132. Platteville limestone, 365. Point Levis, Fossils from, 246. Pondsville, 59. Potomac River, 32, 53, 54, 57, 82, 147, 132, 161. Potsdam sandstone, 27, 74. Powell Mountain, 163. Preface, 19. Prosser, C. 8, 34, 42. Prosser limestone, Fossils from, 216. Proterozoic limestones, 84. Pulaski shale, 171, 275, 287, 288. Fossils from, 325. Q Quebec, Fossils from, 246. Queenston-Richmond formations, 171. R Raver’s Run, Fossils from, 233. Raymond, P. E#., 127, 351. Cited, 238, 239, 240, 247, 261, 271, 310, 338, 347, 348. Reading, Pa., Fossils from, 191. Red Medina, 161, 168, 170, 171. Richmond Group, 161, 171, 320. Fossils from, 218, 214. Rickard Mountain, Fossils from, 205, 211, 222, 225, 237, 245, 255, 265, 275, 281, 282, 292, 296, 297, 313, 315, 324, 342, 356, 367, 370, 371, 372. Ridley limestone, 118. Ringgold, 70, 73, 85. Roadside, 66. Rogers, H. D., 37. Rogers, W. B., 38. Rohrersville, 54, 59. Rome, N. Y., Fossils from, 288. Rome sandstone, 68. Rome shale, 68. Ruedemann, Rudolph, 331. Cited, 208, 204, 205, 206, 254, 256, 328, 354, 368. Russell shale, 68. Rysedorph conglomerate, 254, 257, 354, 369. Rysedorph Hill, Fossils from, 369. Ss Safford, J. M., 117. St. Thomas, Pa., Fossils from, 166, 244, 251, 260, 267, 306, 315. Section 2% mi. south of, 148. Salter, J. W., 26. Sapp, E. H., 7. Saratoga, Trilobites of, 76. Saratoga Springs, Fossils from, 191. “ Saratogan,” 74, Saxton, Pa., Fossils from, 233. Scharf, J. T., 38. Schuchert, Charles, 28, 30, 42, 43, 45, 170, 232. Cited, 198, 258, 263. Scofield, W. H., cited, 292, 295, 315. Scotland, Pa., 76, 77. Fossils from, 288, 352. Section of Conococheague limestone west of, 77. Security, 82. Security Cement and Lime Company, 82. Sedgewick, Adam, cited, 25, 26, 27. Seely, H. M., 87. Shady limestone, 66. Sharpsburg, 58, 70, 73, 80. Fossils from, 190. a Shenandoah,” 61. Shenandoah formation, 60. Shenandoah limestone, 60, 66. Shenandoah River, 57. Shenandoah series, 117. Shenandoah Valley, 24. Sherwood limestone, 61, 66. Silurian, Usage of, 33. “ Silurian System,” 25. Singewald, J. T. Jr., 7. Sinuites bed, 141, 145, 150, 164. Fauna of, 165. Sinuites zone, 164. Smithsburg, 68, 70, 71. Fossils from, 234, 339. South Mountain, 24, 53, 54, 56, 58, 61, 62, 64, 65, 69. Stonehenge limestone, 78, 97, 99, 100, 101, 106, 107. Fossils of, 100. Stonehenge member, 82, 93, 96, 106, 114. Stones River, Fossils from, 202, 214, 227, 229, 249, 295. GENERAL Stones River limestone, 49, 63, 92, 95, 105, 108, 110, 117, 145, 146, 148, 149, 150, 151, 152. Areal distribution of, 126. Fauna of, 127, 128. General sections of, 117. Lithologie character of, 121. Paleontology of, 121. Stose, G. W.,-20, 34, 48, 44, 57, 67, 72, 76, 77, 87, 88, 94, 130, 230, 250. Stoufferstown, Fossils from, 291, 293, 294, 302, 308, 327, 331. Strasburg, Va., 153, 163. Fossils from, 197, 232, 235, 243, 257, 267, 316, 317, 321, 355, 358, 373. Sugar Loaf Mountain, 56, 113. Swartz, C. K., 7, 44. Sword Mountain, 172. T Taconic system, 27. Taylor, R. C., 36. Tennessee, 83, 117, 126, 127. Cedar glades of, 121. Fossils from, 197, 206, 224, 227, 229, 230, 238, 239, 248, 249, 272, 298, 300, 344. Tetradium cellulosum bed, 133, 136, 144, 145, 146, 147, 148, 149, 150, 151, 152, 158, 154. Fauna of, 137. Tomstown formation, 73. Tomstown limestone, 48, 58, 61, 64, 65, 88, 89. Age of, 66. Areal distribution of, 65. Correlation of, 66. Economic features of, 64. Lithologic characters of, 62. Residual products of, 63. Topography of, 61. Tomstown-Waynesboro boundary, 69. Tomstown Valley, 65. “ Transition” beds, 129. “Transition Series,” 25, 26. Trenton age, 141, 156, 163, 165. Trenton Falls, Fossils from, 235. Trenton formation, 112 154, 157. Trenton limestone, 27. Fossils from, 197, 202, 203, 205, 232, 235, 269, 270, 315, 323, 827, 330, 333, 350, 351, 353, Tribes Hill limestone, Fossils from, 329, 346, 362. Tribes Hill limestone fauna, 99, 100. Trilobites, 76, 82, 89, 103, 113. Turner’s Gap, 53. 226, 326, 354. 192, INDEX 415 Turritoma zone, 98, 95, 96, 104. Fossils of, 105. Tuscarora Mountain, 168, 172. Fossils from, 169, 222, 225, 242, 251, 258, 266, 272, 275, 276, 282, 283, 284, 285, 287, 288, 289, 296, 325, 334, 356, 372. Section along west slope of, 173. Tuscarora sandstone, 171, 172. Tyson, P. T., 37. U Ulrich, E. 0., 20, 28, 29, 30, 31, 34, 42, 43, 45, 47, 74, 87, 88, 93, 94, 99, 101, 11%, 122, 124, 130, 121, 132, 137, 139, 142, 144, 146, 153, 163, 171, 172, 356. Cited, 213, 214, 216, 219, 224, 226, 227, 228, 229, 278, 281, 286, 292, 295, 296, 311, 334, 365, 368, 370. Upper Chazyan, 154. Upper Maysville, 157, 161, 171. Upper Medina, 171. Upper Ordovician shales, 154, 161. Upper Stones River, 126, 140, 144. Utah, Fossils from, 238. Utica shale, 27, 156. Fossils from, 231. Vv Valley limestone, 60. Vanuxem, Lardner, 304. Cited, 303. Vermont, 90. Fossils from, 297, 302, 332. Virginia, 24, 61, 67, 83, 103, 111, 118, 126, 130, 142, 163, 167. Fossils from, 190, 191, 194, 217, 234, 254, 257, 267, 272, 277, 292, 297, 345. WwW Wagner’s Cross Roads, 63, 70. Walcott, C. D., 40, 41, 59, 66, 74, 84, 86, 235, 319. Cited, 32, 238, 351. Walling, H. F., 39. Washington County, Fossils from, 204, 234, Warrior limestone, 83. Waucoban fossils, 89. Wautaga shale, 67, 68. Waynesboro, 57, 66, 67, 69, 74. Fossils from, 230, 319, 339. 416 GENERAL Waynesboro formation, 48, 63, 65, 66, 72, 73, 88, 89. Age of, 71. Areal distribution of, 70. Correlation of, 71. Weonomic features of, 71. Lithologic character of, 68. Name and synonymy of, 67. Thickness of, 68. Tomstown-Waynesboro boundary of, 69. Waynesboro sandstone, 61. Weller, Stuart, 303. Cited, 195, 234, 236, 241, 243, 248, 249, 268, 270, 273, 315, 314, 315, 321, 335, 345, 353, 355, 358, 359, 362. Wenlock, 26. West Virginia, 123, 151, 153. Western Maryland Railway, 58, 62, 65, 72, 80, 86, 99, 103, 139, 156, 161, 167. _Weverton, 54. Weverton quartzite, 53, 88. Weverton sandstone, 48, 54, 61, 113. Composition of, 55. Outerops in, 54. Thickness of, 56. INDEX White Medina (Tuscarora) sandstone, 168, 171. Whitfield, R. P., cited, 283, 285, 288, 367, 370, 372. Williams, G. H., 41. Williams, R. C., 20. Williamsport, 110, 156, 158, 161, 167. Exposures in, 103. Fossils from, 203, 206, 231, 236, 246, 267, 290, 292, 297, 299, 308, 316, 336, 340, 342, 363, 372. Willis, Bailey, 41, 44. Wilson, Alice, 267. Wilson, Md., 182, 139, 141, 144, 151. Fossils from, 194, 201, 208, 213, 214, 217, 220, 240, 241, 248, 263, 264, 268, 349, 365. Winchell, N. H., 117, 232. Cited, 198, 258, 263. Wing, Mr., 87. ‘““Wing Conglomerate,’’ 87. Wisconsin, Fossils from, 197, 330. Woods, A. F., 5. Y York, Pa., Fossils of, 66, 88. PALEONTOLOGICAL INDEX Figures in bold face indicate principal discussion. A Acidaspis, 355. ulrichi, 117, 182, 355. Acrotretide, 234. Actinoceratide, 328. Actinostroma trentonensis, 192. Alecto inflata, 212. Alge, 82, 85, 189. Allonychia, 284. ovata, 170, 178, 284. Ambonychia cincinnatiensis, 282. radiata, 282, Ambonychiide, 282. Amphilichas, 354. ef. trentonensis, 136. trentonensis, 165, 166, 182, 354. Amphion salteri, 359. Ampyx, 336. ef. A. normalis, 142. halli, 124, 337. (Lonchodomas) halli, 128, 182, 337. (Lonchodomas) normalis, 140, 180, 336. normalis, 336. Amygdalocystide, 141. Anastrophia hemiplicata, zy. Anodontopsis (Modiolopsis) unionoides, 281. unionoides, 281. Anolotichia, 135. Anthozoa, 198. Aparchites, 137, 366. minutissimus, 169, 182, 366. Archeocyathus, 66. Arthroclema spiniformis, 228. Arthropoda, 332. Arthropora, 224. bifurcata, 143, 176, 224. cleaveland, 169, 176, 225. Arthrostylidx, 227. Asaphellus, 345. gyracanthus, 100, 182, 345. Asaphide, 342. Asaphus canalis, 345. convexus, 347. gyracanthus, 347. (Isotelus) megistos, 343. marginalis, 346. trentonensis, 354. Aspidobranchia, 289. Atremata, 2380. Atrypa exigua, 273. hemiplicata, 269. modesta, 274. plena, 270. recurvirostris, 272. Avicula demissa, 284. Aviculide, 284. Bathyuride, 340. Bathyurus, 136, 347. caudatus, 340. conicus, 340. levis, 347. Bastostoma, 220. cf, B. magnoporum, 135. irrasa, 218. jamesi, 169, 174, 220. Batostomellide, 221. Beatricea, 137, 148, 150. Bellerophon bilobatus, 313. cancellatus, 313. sulcatinus, 309. Berenicea, 214. vesiculosa, 169, 174, 214. Beyrichia chambersi, 369. Beyrichiide, 367. Billingsellide, 237. Bolboporites, 141. Brachiopoda, 230. Branchiopoda, 362. Bryozoa, 212, 220. Bucania, 309. champlainensis, 309. sulcatina, 124, 128, 180, 309. Bucaniide, 309. Bumastus, 351. milleri, 351. trentonensis, 164, 166, 182, 351. Byssonychia, 282. precursa, 170, 178, 283. radiata, 178, 282, 283. vera, 169, 178, 282. Bythocypris, 371. cylindrica, 169, 182, 371. Bythopora, 221. arctipora, 169, 174, 221. 418 PALEONTOLOGICAL INDEX Cc Calcareous Alge, 82, 193. Callopora onealli sigillaroides, 222. sigillarioides, 222. Calymene, 356. becki, 342. callicephala, 356. callicephala granulosa, 356. granulosa, 169, 182, 356. senaria, 164, 166, 182, 357. Calymenide, 356. Camarocladia, 196. rugosa, 174, 196, 137. Camarotoechia, 270. plena, 135, 136, 178, 270. Camerata, 209. Camerella minor, 233. Cameroceras, 117, 180, 321. Carabocrinus, 135, 142, 174, 209. Caritodens demissa, 284. Caryocaris, 372. silicula, 167, 182, 372. Caryocystites, 133, 135, 174, 208, 209. Catazyga erratica, 275. Cephalopoda, 321. Ceratopea, 93, 95, 103, 299. keithi, 104, 178, 299. Ceratopsis, 369. chambersi, 169, 182, 369. Ceraurus, 358. pleurexanthemus, 137, 142, 182, 358. Cerionites, 194. Chetetes, 201. jamesi, 220. sigillarioides, 222. Chetetide, 199. Chasmatopora, 226. reticulata, 136, 176, 226. sublaxa, 136, 176, 227. Cheiruride, 358. Christiania, 256, 257. Jamellosa, 165, 166, 176, 257. trentonensis, 142, 143, 152, 176, 256. Cirripedia, 371. Clathrospira, 137. Cleiocrinus, 137, 149, Clidophorus, 280, 320. planulatus, 169, 178, 280. Cliftonia, 267. Climacograptus, 202. bicornis, 169, 174, 208, 204. putillus, 167, 174, 202. spinifer, 167, 174, 203. typicalis, 203. Clitambonitidse, 268. Celenterata, 198. Coleolus, 320. iowensis, 164, 165, 166, 180, 320. Columnaria, 198. alveolata, 198. halli, 135, 174, 198. Conotreta, 234. rusti, 164, 166, 176, 234. Constellariide, 217. Conularia, 320. trentonensis, 164, 166, 180, 320. Conulariida, 319. Conulariide, 320. Cornulites, 276. flexuosus, 169, 178, 276. Corynexochide, 338. Corynoides, 157, 206. calicularis, 165, 167, 174, 206. Corynotrypa, 212. delicatula, 142, 174, 213. inflata, 142, 174, 212. Craniide, 236. Crinoidea, 209. Crustacea, 332. Cryptolithus, 143, 333. bellulus, 169, 180, 333. recurvus, 169, 180, 334. tesselatus, 164, 165, 167, 180, 335. Cryptostomata, 223. Cryptozoon, 76, 82, 83, 85, 86, 89, 101, 102, 106, 107, 189, 190, 191. proliferum, 78, 82, 85, 89, 174, 189, 190. steeli, 98, 94, 95, 102, 174, 191. undulatum, 78, 82, 89, 174, 190. Ctenodonta, 143, 277, 279. ef. C. gibberula, 136, filistriata, 169, 178, 279. gibberula, 137, 178, 277. levata, 279. obliqua, 169, 178, 278, 320. Ctenodontide, 277. Cyathocrinide, 209. Cyathophyllide, 198. Cyathophyllum profundum, 199. Cycloceratide, 325. Cyclonema, 316, 317. Cyclora, 316. hoffmanni, 164, 165, 166, 180, 317. minuta, 164, 165, 166, 167, 180, 279, 316, 317, 320. parvula, 164, 165, 166, 180, 316. Cyclostomata, 212. Cyclostomiceras, 331. cassinense, 100, 180, 331. Cyphaspis, 353. matutina, 164, 165, 166, 182, 353. Cypricardites nasuta, 289. Cypride, 371. Cyrtoceras, 329. beekmanense, 100, 180, 330. camurum, 144, 180, 330. PALEONTOLOGICAL INDEX 419 gracile, 100, 180, 329. kirbyi, 328. Cyrtocerina, 331. mercurius, 105, 331. Cyrtochoanites, 32S. Cyrtodonta, 122, 136, 137. Cyrtodontide, 281. Cyrtolites (Microceras) inornatus, 312, trentonensis, 306. Cyrtolitide, 311. Cyrolitina, 311. nitidula, 165, 180, 311. Cystoidea, 207. Cytherina fabulites, 364. D Dalmanella, 94, 2-42. edsoni, 165, 166, 176, 243. electra, 104, 105, 176, 245. multisecta, 169, 176, 2-44. (Orthis) wemplel, 246. subequata, 249. testudinaria, 140, 142, 164, 165, 166, 176, 242, testudinaria var, multisecta, 244. wemplei, 99, 100, 176, 246. Dendrocrinide, 211. Dianulites, 217. petropolitana, 217. petropolitanus, 140, 174, 217. Diastoporide, 212. Dikelocephalidw, 351. Dinorthis, 247. ef. D. subquadrata, 143. pectinella, 140, 176, 248. (Plesiomys) platys, 128, 176, 247. platys, 124, 247. Diplograptide, 202. Diplograptus, 205. foliaceus mut vespertinus, 205. pristis, 205. vespertinus, 169, 174, 205. Diplotrypa, 141, 219. appalachia, 141, 142, 149, 174, 219. Discinide, 234. Dolichometopus, 74, 89, 182, 338. Drepanella, 367. macra, 187, 182, 367. E Eccyliomphalus, 305. multiseptarius, 100, 180, 305. trentonensis, 165, 166, 180, 306. triangulus, ov2. Eccyliopterus, 94, 301. disjunctus, 105, 180, 301. triangulus, 102, 180, 302. Echinodermata, 207. Echinospherites, 139, 144, 152, 207. aurantium americanum, 139, 143. 174, 207. Echinus aurantium, 207. Endoceratide, 321. Eoharpes, 332. ottawaensis, 164, 166, 180, 332. Eoorthis, 237. cf, desmopleura, 82, 89, 176. desmopleura, 237. remnicha, 237. wichitensis, 237. Escharopora, 223. cf. ramosa, 140. confluens, 136, 174, 223. Eucrustacea, 362. Eunema cf. E. salteri, 137. Euomphalide, 297. F Favosites, 201. Fucoides linearis, 276. G Gastropoda, 289. Girvanella, 122. Gomphoceras cassinense, 331. Gonioceras, 328. chaziense, 136, 180, 328. Goniurus, 340. caudatus, 104, 182, 3140. Graptodictya, 136. Graptolite germs, 206. Graptolithus bicornis, 204. putillus, 202. Graptolitoidea, 202. Graptoloidea, 202. H Hallopora, 222. onealli sigillaroides, 169, 174, 222. Halloporids, 222. Harpedide, 332. Harpina ottawensis, 332. Hebertella, 23S. pellarugosa, 136, 140, 176, 239. borealis, 124, 128, 136, 176, 238. vulgaris, 124, 128, 135, 136, 176. 239. Helicotoma, 122, 300. planulata, 300. planulatoides, 137, 150, 178, 300. 301. verticalis, 137, 178, 301. Helopora, 227. divaricata, 136, 176, 227. spiniformis, 139, 176, 228. 420 PALEONTOLOGICAL INDEX Hemigyraspis, 346. collieana, 100, 182, 346, Hemiphragma, 218. cf. H. irrasum, 143. irrasum, 136, 140, 174, 218. Heterocrinide, 210. Heterocrinus, 210. heterodactylus, 169, 174, 210. Hlindia, 197. parva, 165, 166, 174, 197. spheroidalis, 197. Hindiidae, 197. Hippothoa, 212. delicatula, 213. Holochoanites, 321. Holopea, 316. nana, 316. Hormotoma, 291, 31/. artemesia, 104, 178, 291. gracilens, 105, 178, 293. gracilis, 169, 178, 292. Hudsonaster, 211. clarki, lov, 174, 211. matutinus, 211. Hudsonasteridx, 211. Hyolithide, 318. Hyolithes, 318. communis, 59, 89, 180, 318. Hypoparia, 332. Hystricurus, 340. conicus, 102, 182, 340. Illenide, 349. Illenurus columbiana, 347. Illenus, 142, 148, 349. americanus, 165, 166, 182, 349. Inadunata, 209. Intricaria reticulata, 226. Ischadites, 139, 194. Ischyrodonta, 281. curta, 281. unionoides, 170, 178, 281. Isochilind, 363. amiana, 363. cf. I. gracilis, 136, 137. ef. I. ottawa, 137. gregaria, 104, 182, 363. ottawa var. intermedia, 363. seelyi, 105, 182, 363. Isotelus, 117, 137, 182, 342, 345, 348. eanalis, 345. gigas, 143, 182, 342, 343, 344. maximus, 343. megistos, 170, 182, 343. stegops, 169, 182, 342. K Kledenia, 137. Ledida, 280. Leperditella, 366. tumida, 137, 182, 366. Leperditia, 150, 151, 364. bivertex, 370. ef. L, fabulites, 186, 140, 142. fabulites, 122, 124, 127, 128, 129, 137, 152, 182, 364. (Isochilina) cylindrica, 371. (Isochilina) minutissima, 366. tumida, 366. Leperditiide, 363. Lepidocoleide, 371. Lepidocoleus, 143, 371. jJamesi, 167, 169, 182, 371. Leptena, 142, 149, 257, 260. alternata, 265. ef. L. charlotte, 143. charlotte, 136, 176, 250, 257. gibbosa, 169, 176, 259. rhomboidalis, 258. sericea var, rugosa, 255. tenuistriata, 165, 166, 176, 260. Leptobolus, 230. insignis, 167, 176, 231. ovalis, 164, 165, 166, 176, 230. Lichadide, 354. Lichenaria, 220, Licrophycus cf. L. ottawaense, 139. Lingula, 151, 232. elderi, 233. (Glossina) riciniformis, 232. nicklesi, 170, 176, 232. rectilateralis, 233. riciniformis, 164, 165, 166, 176, 230, 232. Lingulella, 71, 89, 176, 230. Lingulide, 232. Liospira, 93, 104, 296. ef. perangulata, 122. micula, 169, 170, 178, 296. Lituites internistriatus, 326. Lockeia, 139. Lonchodomas halli, 337. Lophospira, 294. bicincta, 124, 128, 178, 294. ef, L. procera, 137. (Ruedemannia) lirata, 169, 178, 295. (Seelya) lirata, 295, trochonemoides, 122. Lyrodesma, 286. conradi, 169, 178, 286. Lyrodesmidx, 286. M Maclurea, 299. magna, 297. oceana, 299. sordida, 298. PaLEONTOLOGICAL INDEX 421 Maclurites, 94, 98, 108, 104, 297. affinis, 102, 178, 297. magna, 297. magnus, 118, 120, 124, 128, 178, 297. oceanus, 105, 178, 299. sordida, 93. sordidus, 104, 178, 298. Macronotella, 368. ulrichi, 137, 182, 368. Malacostraca, 372. Matheria, 122, Merocrinus, 169, 174, 211. eurtus, 211. Mesonacide, 339. Mesotrypa, 142. Microceras, 312. inornatum, 164, 165, 166, 180, 312. Modiolodon, 288. truncatus, 170, 178, 288. Modiolopside, 286. Modiolopsis, 286. modiolaris, 170, 178, 286. nasutus, 289. truncatus, 288. Mollusca, 277. Molluscoidea, 212. Monotrypa (Chetetes) cumulata, 217. Monticulipora (Heterotrypa) jamesi, 220. wetherbyi, 214. Monticuliporide, 214. Murchisonia acrea, 293. alexandra, 308. artemesia, 291. bicincta, 294. gracilens, 293. gracilis, 292. N Nautiloidea, 321. Neotremata, 233. Nicholsonella cf. N. laminata, 135. Nidulites, 141, 144, 193. pyriformis, 141, 174, 193, 220. Notostraca, 362. Nucula obliqua, 278. Nuculites, 362. planulata, 280. Oo Obolella, 232, 233. minor, 59, 89, 176, 233. Obolellide, 233. Obolidz, 230. Odontopleuride, 355. Olenellus, 66, 71, 339. thompsoni, 59, 89, 182, 339. Olenide, 341. Omospira, 308. alexandra, 137, 180, 308. Onchometopus, 348. obtusus, 348, simplex, 142, 182, 348. suse, 348. Oncoceras, 122. Oncoceratide, 331. Ooceras, 328. kirbyi, 100, 180, 328. Ophileta, 94, 95, 98, 302. compacta, 102, 180, 304. complanata, 99, 100, 180, 302, 303, 304, 305. discus, 304. disjuncta, 301. levata, 100, 180, 304. Opisthobranchia, 318. Opisthoparia, 338. Orbicula filosa, 235. lamellosa, 234. Orbiculoidea, 234. lamellosa, 1438, 176, 234. Orbignyella, 214. wetherbyi, 137, 174, 214. Orocystites, 139, Orthacea, 237. Orthide, 238. Orthis, 240. ' bellarugosa, 239, borealis, 238. (Dalmanella) subequata, 249. desmopleura, 237. (Dinorthis) pectinella, 248. electra, 245. emacerata var. multisecta, 244. erratica, 275. (Hebertella) bellarugosa, 239, linneyi, 271. merope, 268. multisecta, 244, pectinella, 248. platys, 247. (Plectorthis) desmopleura, 237. plicatella, 241. subequata, 249. testudinaria, 242. tricenaria, 142, 143, 176, 240. Orthoceras, 122, 187, 322, 323. arcuoliratum, 144, 180, 323. junceum, 164, 165, 166, 180, 323. lamellosum, 170, 180, 324. primigenium, 100, 180, 322. transversum, 169, 180, 324. Orthoceratide, 322. Orthochoanites, 322. Orthodesma, 289. nasutum, 170, 178, 289. Orthorhynchula, 271. linneyi, 157, 160, 168, 170, 178, 271. Ostracoda, 363. 422 PALEONTOLOGICAL INDEX Oxoplecia, 267. calhouni, 267. Pp Pachydictya cf. P. robusta, 136. Paleophycus, 141, 192. tubulare, 100, 174, 192. Parastrophia, 269. hemiplicata, 143, 178, 269. Paterula, 231. Pelecypoda, 277. Pentameracea, 267. Phacopide, 360. Phacops callicephalus, 360. Pholidops, 236. cincinnatiensis, 169, 176, 236. Phyllocarida, 372. Phylloporina reticulata, 226. sublaxa, 227. Phylloporinide, 226. Phytopsis cellulosum, 202. Pianodema, 249. cf. P. subequata, 142, 149, subeequata, 140, 176, 249. Plesiomys platys, 247. Platymetopus trentonensis, 354. Platystrophia, 266. Plectambonites, 136, 140, 142, 143, 253, 255, 257. cf. P. pisum, 142. cf. P. sericeus, 149. pisum, 140, 143, 176, 253. rugosus, 169, 176, 255. Plectorthis, 241. aff. P. Whitfieldi, 142. plicatella, 169, 170, 176, 241, 242. Pleurocystide, 141. Pleurotomaria, 289, 290, 291. canadensis, 104, 178, 289. floridensis, 178, 291. gregaria, 105, 178, 290. hunterensis, 302, 303. laurentina, 308. micula, 296. Pleurotomariide, 289. Pliomerops, 359. salteri, 104, 182, 359. Plumulites jamesi, 371. Polygyrata, 303. Porambonitide, z69. Porifera, 195. Porocrinus, 142, Prasopora, 215. contigua, 142, 174, 216. insularis, 140, 174, 215. Primitia, 137. gregaria, 363. seelyi, 363. Prion odesmacea, 277. Proetide, 352. Proetus, 352. latimarginatus, 164, 166, 182, 352. Proparia, 356. Protorhyncha, 1387, Protowarthia cancellata, 313. granistriata, 314. Protozyga exigua, 273. Protremata, 237. Pterinea, 284. (Caritodens) demissa, 170, 178, 284. demissa, 284. modiolaris, 286. Pteropoda, 318. Pterygometopus, 360. callicephalus, 1387, 182, 360. ef. P. callicephalus, 142. cf. P. schmidti, 140. Ptilodictya arctipora, 221. cleavelandi, 225. Ptilodictyonide, 223. R Rafinesquina, 140, 261. alternata, 170, 176, 258, 264, 265. cf. R. incrassata, 142. champlainensis, 136, 176, 261. minnesotensis, 140, 176, 261, 264. minnesotensis inquassa, 140, 176, 264. squamula, 169, 170, 176, 264, Raphanocrinus, 139. Raphiophoride, 336. Raphistoma, 307. columbianum, 100, 180, 307. obtusum, 100, 180, 307. Raphistomide, 307, Raphistomina, 308. laurentina, 104, 180, 308. Receptaculites, 194. occidentalis, 139, 174, 194. Reteocrinide, 209. Reteocrinus, 117, 174, 209. Rhabdaria, 195. fragilis, 102, 174, 195. Rhinidictya, 229. ef. R. neglecta, 143. fidelis, 136. neglecta, 140, 176, 229. Rhinidictyonide, 229. Rhipidomellide, 247. Rhynchonellacea, 270. Rhynchonellide, 270. Ribeiria, 362. nuculitiformis, 100, 184, 362. Ruedemannia lirata, 295. PALEONTOLOGICAL INDEX 423 Ss Salterella, 66, S89, 180, 319. Saukia, 351. fallax, 351. pepinensis, 351. stosei, 82, 89, 182, 351. Scenidium, 268. anthonense, 142, 178, 268. anthonensis, 268. ef. S. anthonense, 143. halli, 268. merope, 165, 166, 175, <6s. Schizocrania, 235. filosa, 167, 176, 235. Scolithus, 57, 276. linearis, 58, 89, 175, 276. Sinuites, 157, 158, 313. cancellatus, 163, 164, 165, 166, 169, 180, 318, 314. granistriatus, 164, 165, 166, 169, 180, 314. Sinuitide, 313. Solenopleuride, 340. Solenopora, 192. compacta, 122, 135, 148, 174, 192, 193. spongioides, 192. Spongiz, 193. Spyroceras, 325. bilineatum, 165, 166, 180, 325. Stelleroidea, 211. Stenopora fibrosa, 195. Stictopora paupera, 229. Stictoporella, 142. Stomatopora proutana, 213. tenuissima, 213. Streptelasma, 199. profundum, 137, 174, 199. Streptorhynchus hallie, 251. Stromatotrypa, 142. Strophomena, 143, 250. alternata, 265. cf. S. emaciata, 137. cf. S. filitexta, 140, 142. deltoidea, 261. gibbosa, 259. hallie, 169, 176, 251, 257. (Hemipronites) sinuata, 252. inquassa, 264. sculpturata, 164, 165, 166, 176, 250. sinuata, 169, 176, 250, 252. squamula, 264. stosei, 117, 176, 250. Strophomenacea, 250. Strophostylus, 315, 316. textilis, 165, 166, 180, 315. Symphysurus, 347. econvexus, 100, 182, 347. Syntrophia, 267. lateralis, 93, 102, 104, 178, 267. T Tabulata, 199. Tellinomya obliqua, 278. ventricosa, 277. Telotremata, 270. Tentaculites flexuosa, 276. Tetrabranchiata, 321. Tetracoralla, 198. Tetractinellida, 197. Tetradium, 121, 199, 200. cellulosum, 133, 136, 137, 148, 149, 150, 174, 202. columnare, 135, 174, 201. peachii var. canadense, 192. simplex, 102, 174, 199. syringoporoides, 122, 124, 126, 127, 128, 129, 152, 174, 200. Tetranota, 310. bidorsata, 310, 311. obsoleta, 169, 180, 310. Thallophyta, 189. Torellellide, 319. Trematide, 235. Trematopora cf, primigenia, 143. Trematoporide, 218. Trepostomata, 214. Tretaspis, 143. Triarthrus, 341, 342. becki, 164, 165, 166, 167, 169, 182, 341, 342. fischeri, 164, 166, 182, 341. Trilobita, 332. Trinucleide, 333. Trinucleu3 concentricus, 335, 336. Triplecia, 266, 267. ef. T. nucleus, 143. (Cliftonia) simulatrix, 140, 142, 143, 165, 166, 178, 266. lateralis, 267. Trocholites, 326. ammonius, 164, 166, 180, 327. internistriatus, 105, 180, 326. Trocholitide, 326. Trochonematida, 315. Tubicola, 276. Turbo parvulus, 316. Turritella, 293. Turritoma, 104, 293. acrea, 104, 105, 178, 293. U Ulrichia, 370. bivertex, 169, 182, 370. 424 PALEONTOLOGICAL INDEX Vv Zz Vermes, 276. Zaphrentide, 199. : “ygospira, 272. erratica, 170, 178, 275. w exigua, 143, 178, 273. Wingia, 87. modesta, 169, 170, 178, 274, 275. Worm burrows, 276. recurvirostris, 136. 137, 178, 272.