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 DOCUMENTS 
 DEPT. 
 
 UC-NRLF 
 
ants 
 
U. S. GEOGRAPHICAL AND GEOLOGICAL SURVEY OP THE ROCKY MOL\T\L\ REGION. 
 
 J. W. FOWELL, IN CHARGKE. 
 
 PRELIMINARY REPORT 
 
 OX THE 
 
 PALEONTOLOGY OF THE BLACK HILLS, 
 
 K. P. WHITFIELD, 
 
 CONTAINING DESCRIPTIONS OF NEW SPECIES OF FOSSILS FROM THE 
 
 POTSDAM, JURASSIC, AND CRETACEOUS FORMATIONS | 
 
 OF THE BLACK HILLS OF DAKOTA. 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 July, T877. 
 
S. GEOGRAPHICAL AND GEOLOGICAL SURVEY OF THE ROC1Y MOUNTAIN REGION. 
 
 J. W. FO^VELL, IN CHARGJ-H5. 
 
 PRELIMINARY REPORT 
 
 OX THE 
 
 PALEONTOLOGY OF THE BLACK HILLS, 
 
 BY 
 
 R. 
 
 CONTAINING DESCRIPTIONS OF NEW SPECIES OF FOSSILS FROM THE 
 
 POTSDAM, JURASSIC, AND CRETACEOUS FORMATIONS 
 
 OF THE BLACK HILLS OF DAKOTA. 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 
 July, 1877. 
 
NOTE. 
 
 The new species of fossils described in this preliminary report, by 
 Professor E. P. Whitfield, from the Potsdam, Jurassic, and Cretaceous 
 formations, are such forms as are new to science in the collections made 
 by W. P. Jenney and H. Newton during the exploration of the Black 
 Hlls of Dakota in the summer of 1875. 
 
 These forms, with many others from the same formations, are em- 
 bodied in the final report on the paleontology of this region, which, 
 with sixteen lithographic plates, will accompany the publication of the 
 final results of the exploration in the Black Hills. 
 
 July, 1877. 
 
DOCUMENT 
 DEPT. 
 
 PRELIMINARY REMARKS. 
 
 The species described in the followiDg pages were collected in and 
 around the Black Hills during the expedition, and represent the differ- 
 ent formations recognized, except the Carboniferous, from which the 
 fossils obtained were few and of little interest. 
 
 The horizon of the Potsdam formation of the Black Hills appears to 
 be, so far as the fossils will serve to determine, about the same as that 
 of Wisconsin and the neighboring States ; and of some of the layers 
 the lithological features are so nearly the same that it would be difficult 
 to distinguish between specimens from the two localities. The purplish- 
 green quartzitic rock from the head of Red Caiion Creek, containing 
 Lingulepis pinniformis Owen sp. and several other Brachiopodous shells, 
 appears to hold nearly the same relation to the rest of the group as 
 does that at the Falls of the St. Croix, from which the species was orig- 
 inally described, namely, near the base ; the Eed Caiion Creek beds 
 resting immediately on the slates of older date (probably Huronian) 
 while the Trilobitic beds and the soft friable layers occur at a horizon 
 of about 100 feet below the Carboniferous. The entire fauna of the 
 Black Hills beds closely resembles that from Wisconsin ; although the 
 species are nearly all distinct, the generic facies is the same through- 
 out. Among the fossils from the higher parts of the formation there 
 are quantities of Plant remains belonging to the genus Palceophycus 
 which, I am informed, cover the surface of the rocks over large areas 
 where exposed, being densely matted together. These beds also hold a 
 position similar to the Plant beds of other localities. 
 
 The Jurassic formations seem also to be well represented in this region, 
 'and many of the beds are highly fossil if ero us. The species are not 
 numerous, but the individuals are extremely abundant, many of the 
 slaty calcareous layers being so largely composed of organic remains, 
 mostly Lamellibrauchiates, as to be quite friable and easily broken in 
 the hand, and some of the sandy layers have their surfaces densely cov- 
 ered with the separated shells of one or two species. The absence of 
 Gasteropoda is a noticeable feature at all localities from which specimens 
 have been brought, no example of this class of molluscs being present 
 in the entire collections from this formation. The few species of Fresh- 
 water Gasteropoda described, as probably from this horizon, in the 
 Smithsonian Contributions, (Pal. Up. Missouri,) being still doubtfully 
 referred. This same absence of Gasteropoda is also noticed in all the 
 collections of Jurassic age we have seen from the western countries. 
 
 3 
 
not more than three or four species having been obtained beyond those 
 above referred to. 
 
 Among the Cretaceous fossils there are many forms of great interest, 
 especially among the Inocerami and Cephalopoda. Among the former 
 the forms described under the new generic name of Endocostce are in- 
 teresting as affording light on a group of shells that, although long 
 known, have not been fully understood, probably owing to the want of 
 more and better material which this collection has afforded, the feature 
 there described having been seen on isolated specimens, poorly pre- 
 served. 
 
 Among the Cephalopods of the Cretaceous there are some fine exam- 
 ples of the aberrant forms of the Ammonite group, which show very 
 conclusively that a rich field awaits the future collector in this region. In 
 some of the localities of this formation, from which collections have 
 been brought, there appears to be a difficulty in recognizing the divis- 
 ions of the group, proposed by Messrs. Meek and Hayden, as the fossils 
 of two of the divisions are found intermingling at the same place and 
 in the same layers. The specimens brought from the locality, on Old 
 Woman's Fork of the Cheyenne, are of this character, and there seems 
 to be the same trouble among those from certain parts of Beaver Creek. 
 The collection affords no specimens belonging strictly to the Divisions 
 No. 1 and No. 3, though the beds were observed but not collected from. 
 
FOSSILS FROM THE PRIMORDIAL ROCKS. 
 
PLANTS. 
 
 GENUS PAL^EOCHOKDA. 
 
 PALJEOCHORDA PRIMA, n. sp. 
 
 Plate 1, fig. 2. 
 
 Plants, the remains of which, as preserved on the surface of the rock, 
 consist of narrow, linear, grass-like stipes, coiled or twisted without 
 any regular order, leaving by their removal or decomposition flattened 
 depressions of from one line to two lines in width and of an indefinite 
 length, with rounded or obtusely- pointed extremities. 
 
 The examples in the collection before us are coiled, forming irregular 
 curves, usually enrolled, but sometimes sigmoidal. The surfaces are 
 smooth and structureless, presenting no marking whatever, although 
 the substance is usually of a somewhat lighter color than the surround- 
 ing rock. The terminations are usually sharply rounded, and the whole 
 appearance is more that of the impression of an Annelid than of a plant, 
 though it is difficult to conceive of the preservation of anything other 
 than a plant to leave such markings. We have referred them to the 
 above genus, presuming them to be congeneric with those figured by 
 Professor McCoy in his Synopsis British Palaeozoic Fossils, plate 1 A, 
 fig. 3, although they are not elevated or rounded bodies, but flattened 
 stipes. 
 
 Formation and locality. In the plant beds of the Potsdam formation 
 (probably Upper Potsdam or Calciferous), Head of Red Water Valley, 
 Black Hills, Dakota. 
 
 GENUS PALJ]OPHYCUS, Hall 
 
 PAL^EOPHYCUS OCCIDENTALS, n. sp. 
 
 Plate 1, fig. 3. 
 
 Remains consisting of strong, subcylindrical, flexuous stems or roots, 
 covering the surface of the sandstone. The steins are more or less 
 rounded, although frequently quite flattened, and varying in diameter 
 from one-fourth of an inch to one inch, frequently bifurcating and some- 
 times dividing into threes. They are commonly interlaced with each 
 other, but do not appear to coalesce, but are simply overlapped 5 the 
 surfaces, although sometimes quite smooth, are generally marked by 
 indistinct longitudinal pits and ridges of greater or less extent, fre- 
 
 7 
 
quently occurring of an inch in length, while many are merely short, 
 roughened depressions, which give a corrugated surface to the sterns. 
 
 Judging from the specimens in the collection, we should suppose they 
 often attain considerable length, as on a specimen measuring nearly ten 
 inches the variation in diameter is scarcely perceptible, but occasion- 
 ally one will be found to terminate in an obtuse point. 
 
 This species bears some resemblance to Fucoides duplex Hall, (Post. & 
 Whit., Lake Sup., p. 226, pi. A., 23, fig. 1,) but does not present the 
 longitudinal depression along the middle as in that one, except near a 
 bifurcation. It is very similar to P. tubularis Hall,. from the Calciferous 
 Sandstone of Ke\y York ; but is less ridged and has a somewhat differ- 
 ent mode of bifurcation from any of the specimens of that species which 
 we have seen. If a larger number of the New York species were ex- 
 amined, however, it is possible that the resemblance might be much 
 greater than at present supposed. 
 
 Formation and locality. In the plant beds of the Potsdam formation 
 (probably Upper Potsdam or Calciferous). Head of Bed Water Valley, 
 Black Hills, Dakota. 
 
 MOLLUSCOIDA. 
 
 BRACHIOPODA. 
 
 LlNGULEPIS CUNEOL.US, n. sp. 
 Plate 2, figs. 5 and 6. 
 
 Shells small, rather below the medium size, triangularly ovate in out" 
 line, or sometimes subcuneate ; ventral valve triangularly ovate, with 
 a sharp somewhat pointed beak, the width and length about as three 
 and four, and the point of greatest length near the lower third of the 
 length of the valve; cardinal slopes abrupt, scarcely convex; basal line 
 rounded at the sides but nearly straight in the middle ; surface of the 
 valve strongly convex, becoming almost subangular in the upper part 
 dorsal valve much shorter, proportionally, than the ventral, the length 
 but little exceeding the width ; sides and base more rounded and the 
 beak truncate ; surface distinctly convex. 
 
 Surface of the shell apparently smooth, but usually exfoliated, in 
 which condition a few fine radiating lines are visible. 
 
 The shell differs from L. pinnaformis Ovven, in size and in the more 
 distinctly cuneate form of the ventral valve. At first sight, it might be 
 taken for the young of that species, but a little critical examination 
 soon reveals marked distinctions in the truncation of the front margin, 
 and especially in the form of the cardinal slopes, which are rounded 
 and never concave, as in almost all ventral valves of that species. In con- 
 sequence of this latter feature, the beak does not appear so attenuated 
 as in that one, although proportionally quite as long. In the general 
 
surface characters and form of the valves it corresponds with the genus 
 Linyulcpis, although we have not been able to distinguish the muscular 
 impressions. 
 
 Were it not for the difference in the size of the shells, we should be in- 
 clined to think this might be the species figured by Messrs. Meek and 
 Haydeu, (Pal. Upp. Missouri, p. 3, PI. 1, fig. 1 a and &,) as. Dakotensis; 
 but as their figures appear to be of the natural size, we should suppose 
 it to be very distinct, as all the specimens of our shell noticed have 
 been small, none exceeding one-fourth of an inch in length. 
 
 Formation andloeality. In soft, friable sandstone of the Potsdam group, 
 at Red Canon Creek, in the Southwest Black Hills, Dakota. 
 
 LTNGULEPIS PERATTENUATUS, n. si). 
 
 Plate 2, figs. 7-9. 
 
 Shell spatulate or elongate-ovate, becoming acutely pointed toward 
 the beak; sides below the middle of the length of the ventral valve, 
 rounded ; front margin very regularly curved ; cardinal slopes straight, 
 or sometimes slightly convex, greatest width a little more than half the 
 length of the ventral valve and sometimes nearly two-thirds as great. 
 Surface of the ventral valve depressed convex, very slightly subangular 
 along the middle above the lower third of the length, and a little more 
 distinctly so in the upper part. Apex scarcely truncate. Dorsal valve 
 considerably shorter than the ventral, broadly truncated at the upper 
 end, the line of truncation being distinctly arched. Surface evenly con - 
 vex. Structure of the surface of the shell polished, with fine, somewhat 
 lamellose, lines of growth. 
 
 The shell in many points closely resembles L. pinnaformis Owen, but 
 is a proportionally longer shell and not exceeding one-half the size of 
 the adult specimens of that species. When compared in shape, it is 
 more elongate in front, the lower end of the shell forming a section of 
 an ellipse rather than of a circle as in that one; the cardinal slopes are 
 convex and the valves proportionally longer, the apex being more elon- 
 gated in proportion to the size of the body of the shell, but not so nar- 
 row. The two species are associated in the same blocks, and the dis- 
 similarity between examples of the same size is so perceptible that there 
 will not be the slightest difficulty in recognizing them as distinct. 
 
 Formation and locality. In greenish-purple sandstone of the Potsdam 
 formation, at the Headwaters of Red Cafion Creek, southwest Black 
 Hills, Dakota. 
 
10 
 
 ARTICULATA. 
 
 TKILOBITA. 
 
 CALYMENnm 
 
 GENUS CREPICEPHALUS, Owen (?LOGANELLUS, D 
 CREPICEPHALUS (LOGANELLUS) CENTRALIS, n. s}). 
 
 Plate 2, figs. 21-24. 
 
 Species recognized only by the glabella and fixed cheeks, with a few 
 imperfect fragments of the movable cheeks. The former parts, when 
 united, are somewhat quadrangular in outline, broadest at the base and 
 gently narrowing in front ; glabella rounded-conical, higher than wide, 
 the anterior end somewhat sharply rounded ; surface highly convex and 
 marked by three pairs of distinct lateral furrows, which are strongly 
 bent backward in their direction from the margin, and on the larger 
 specimens the posterior pair almost unite in the middle. Occipital fur- 
 row distinct, extending entirely across the base of the head ; occipital 
 ring strong, rounded, and in the older individuals supporting a short 
 spine; dorsal furrows well pronounced, extending with equal clearness 
 in front of the glabella. Fixed cheeks broad, more than equaling one- 
 half the width of the glabella; palpebral lobes small and slightly angu- 
 lar, situated opposite the middle of the glabella; ocular ridges distinct, 
 directed anteriorly in passing from the eye to the dorsal furrow. Frontal 
 limb short, not more than one-third as long as the glabella, one-half of 
 its length formed by the strong, rounded marginal rim and furrow. 
 Facial suture directed gently inward from, the front of the eye lobe to 
 the anterior margin, with but little curvature; behind the eye it is 
 directed backward and outward at an angle of from thirty-five to forty 
 degrees with the occipital line of the head, with a slightly sigmoidal 
 curvature, giving an elongate triangular form to the postero-lateral 
 limbs. 
 
 There is considerable variation in the form and proportions of the 
 glabella among the different individuals in the collection, the larger 
 specimens being proportionally broader and the lateral furrows much 
 more distinctly marked. On the smaller one figured the furrows are 
 not distinct enough to indicate without exaggeration. The presence or 
 absence of an occipital spine is also noticed, dependent apparently on 
 the same cause. It is possible that the two individuals may belong to 
 different species, but from their great similarity in other respects we 
 feel confident that this is not the case. 
 
 This species resembles in some of its characters C. (Batkyurus ?) an- 
 gulatus, H. & W., from the same formation on the west side of Pogonip 
 Mountain, White Pine, Nev., described in Mr. Clarence King's report, 
 but lacks the angular frontal limb of that species, and the facial sutures 
 
11 
 
 converge in front of the eye, while in that one they are slightly diverg- 
 ent. We know of no other species with which it is closely related, 
 unless it should prove to be more nearly related to Agraulus Oiceni, 
 Meek & Hayden, Pal. Upp. Missouri, p. 9, figs. A, B, C, than we are 
 inclined to believe. There are several particulars in which it differs 
 very materially from their figures, and also from the description given, 
 that would at once mark it as distinct, if it were not that the imperfect 
 material in both cases tends to lead to error. The difference in the 
 width of the occipital lobe is a very marked one, and also the length of 
 the frontal limb, while the form of the glabella varies much in being 
 more distinctly conical than in that species. 
 
 Formation and locality. In coarse sandstones of the Potsdam forma- 
 tion, at Castle Creek, West Black Hills, Dakota. 
 
 CREPICEPHALUS (LOGANELLUS) PLAXUS, n. sp. 
 
 Plate 2, fig. 20. 
 
 Glabella and fixed cheeks, when united, subquadrangular in outline, 
 narrowest across the eyes and slightly expanding in front, and more 
 abruptly so posteriorly. Glabella very depressed convex, slightly 
 conical and somewhat squarely truncate in front, the width across the 
 base being equal to about three-fourths of the height above the occipital 
 furrow, and that of the anterior end to about half the height j lateral 
 furrows very faintly marked, oblique, and extending about one-third of 
 the width from the margin. Occipital furrows not strongly marked, 
 extending entirely across the base of the head ; ring narrow, and with- 
 out spine. Dorsal furrows distinct, but not deep, extending around 
 the front of the glabella. Fixed cheeks wide, more than half as wide, 
 opposite the eyes, as the middle of the glabella. Frontal limb of moder- 
 ate length, at least as long as the width of the anterior end of the gla- 
 bella, but its entire extent and anterior margin have not been fully ascer- 
 tained. Facial suture cutting the anterior border at right angles to the 
 margin of the head and directed slightly inward to the eyes, behind which 
 it is directed obliquely backward, at an angle of about 60 with the base 
 of the head, to the occipital furrow, behind which it runs more directly 
 outward. Ocular ridges distinct. Palpebral lobes small and situated 
 behind the middle of the head. 
 
 The species is only known by the glabella and fixed cheeks, and is 
 remarkable only for its general flatness and want of prominent charac- 
 ters. There is no known species from the same formation either in the 
 Wisconsin locality or from the more western regions that is so closely 
 related to it as to be readily mistaken. <?. (L.) quadra-vis, H. & W., 
 of Clarence King's report, from the slates above Call's Fort, North 
 Wahsatach Mountains, is perhaps as closely related as any, but differs 
 in having the glabella more rounded in front and proportionally broader. 
 
 Formation and locality. Associated in the same beds and locality 
 with the preceding species. 
 
FOSSILS FROM THE JURASSIC ROCKS. 
 
 13 
 
RADIATA. 
 
 ECHINODERMATA. 
 
 ASTEROIDEA. 
 
 GENUS ASTERIAS, Linneus. 
 
 ASTERIAS ?DUBHJ3I, n. Sp. 
 
 Plate 3, fig. 3. 
 
 Several impressions of a species of star-fish, apparently of the genus 
 Asterias, are present in the collection from a bed of light-red sandstone, 
 which occurs at a horizon of from 80 to 100 feet above the Triassic red 
 beds. 
 
 The specimens are not in a condition to afford a full description of 
 their specific characters. They are of small size, the rays being from 
 three-fourths of an inch to one and one-fourth inches long, measuring 
 from the center of the body. The rays are slender and flexuous, most 
 of them being more or less curved in their direction and elevated along 
 the middle, as shown on a gutta-percha cast taken in a natural mold of 
 a group of three individuals. The upper surface is subangular, and in 
 structure they are apparently composed of small nodiform plates, placed 
 in longitudinal rows. The center of the body or disk is marked by an 
 obscurely pentangular depression on the upper surface. None of the 
 specimens show the under side of the body or rays, so that the charac- 
 ters of these parts are entirely unknown. 
 
 The species appears to have been some.what abundant, judging from 
 the condition in which they are grouped on the sandstone, and although 
 the specimens are obscure and too imperfect for positive determination 
 and description, it has been thought best to designate them by name, 
 as they will undoubtedly prove a characteristic form over a certain 
 region, and of a limited horizon. The sandstone is marked, on the 
 layers in which they are found, by ripple or wave marks, having a 
 width of about 3 inches, and indicates a near proximity to a shore-line 
 over the area where they were obtained, and that the individuals are 
 probably stranded specimens. A single very imperfect impression of a 
 Lamellibranchiate shell is represented on the same fragments of rock, 
 but too imperfect for determination. 
 
 Formation and locality. In red sandstones of Jurassic age, Park 
 Sands, 70 feet above the red beds, on the east side of Spear-Fish Creek, 
 near its junction with the Bed Water, northeast of Crow Peak, Black 
 Hills, Dakota. 
 
 15 
 
16 
 
 PECTENIDJE. 
 
 GENUS PECTEN, Brug. 
 PECTEN NEWBERRYI, n. sp. 
 
 Plate 4, figs. 12-15. 
 
 Shell of moderate size, suborbicular in outline, erect and subequilat- 
 <eral, the height and length nearly equal. Valves depressed-lenticular 
 in a transverse section when united ; their surfaces depressed- con vex, 
 except along the sides of the valves near the cardinal slopes, where the 
 surface is elevated so as to form a broad, rounded, fold-like border on 
 this part ; with a broad, undefined, shallow depression separating it 
 from the body of the valve. Hinge line short; that of the left valve 
 less than half as long as the shell below ; straight or a very little slop- 
 ing outward from the apex of the valve, which is small, appressed, and 
 not projecting above the line of the hinge. Anterior side of the hinge 
 a little longer than the other, the anterior wing being rounded at the 
 extremity, more than as long again as the height above the body of the 
 valve at its widest part ; separated from the shell below by a very shal- 
 low, rounded byssal notch, and along the surface by a scarcely percepti- 
 ble groove bordering the body of the valve. Posterior wing smaller, 
 triangular, a little obtuse at the outer upper angle, and proportionally 
 somewhat higher or longer on the lateral border than the anterior wing. 
 Surface of the left valve marked, except on the fold and depression 
 bordering the cardinal slopes, by strong, flattened radii, which are vari- 
 able in strength, size, and distance, and are separated by flattened 
 interspaces, usually of greater width than the ribs themselves. The 
 surface is also marked by closely arranged, distinctly elevated, regular, 
 lamellose, concentric lines parallel to the outer margin, and coincident 
 with the lines of growth, and are slightly arched backward in crossing 
 the radii. These latter markings also cover the surface of the folds of 
 the cardinal borders and the cardinal auriculations. 
 
 A single right valve of small size associated with a number of left 
 valves, on the same block, has the same general form and the same 
 fold-like feature of the cardinal slopes, but appears to be entirely desti- 
 tute of the radii on the body of the valve ; and the concentric markings 
 are also much less distinct and regular than on the opposite valve. The 
 anterior wing is also very small and obtusely triangular, but may have 
 been somewhat mutilated. There can be little if any doubt, however, 
 that this right valve belongs to the same species. 
 
 This species may be readily distinguished by the peculiar fold like 
 feature of the cardinal slopes and the character of the concentric mark- 
 ings, being entirely different in these respects from any other of the 
 genus described from rocks of this age. 
 
17 
 
 Formation and locality. In reddish and buff colored argillaceous 
 
 limestones of Jurassic age, at T Spring, west of the Black Hills 
 
 of Dakota. 
 
 PSEUDOMONOTIS (EUMICROTIS) ORBICULATA, 11. sp. 
 Plate 3, figs. 17-19. 
 
 Shell of moderate size, orbicular in outline, nearly equilateral and 
 subdiscoid. Left valve depressed-convex, most rotund just below and 
 anterior to the beak ; beak small, full, slightly incurved, and projecting 
 somewhat above the cardinal border. Anterior wing very short, almost 
 obsolete, the anterior end regularly rounded from its extremity to and 
 along the basal margin ; posterior wing of moderate size and com. 
 pressed, shorter than the shell below, the posterior margin rounding 
 backward from its extremity to near the middle of the length of the 
 valve, thence somewhat regularly rounded to the base. Surface of the 
 valve marked by numerous unequal, slender, and slightly elevated radii, 
 which are separated by wider flattened interspaces ; also by irregular 
 concentric stride of growth, which often give a knotty or roughened sur- 
 face to the radii where crossing them, especially toward the posterior 
 border and near the outer margin. Eight valve less convex than the 
 opposite one, with a smaller inconspicuous beak, which does not project 
 beyond the cardinal line. Anterior side of the hinge line characterized 
 by a small and very obscure wing, which is reduced to a mere point, 
 reaching to not more than one-third of the length of the very short an- 
 terior side of the hinge. The wing is separated from the body of the 
 shell below, as in others of this division of the group, by a narrow and 
 rather deep groove, but not by a distinct sinus. Posterior wing longer 
 and compressed, but not extending to more than half the length of the 
 body of the shell below. Surface of the valve marked, in all cases ob- 
 served, by fainter radii than the left valve, but otherwise of similar 
 character. 
 
 This species is closely related to P. (E.} curta, Hall, but is much larger, 
 several of the individuals measuring seven-eighths of an inch in length, 
 and one specimen measures nearly an inch ; while those of that species 
 seldom attain to more than two-thirds of that size. The shell is also 
 much less oblique; less convex; the radii sharper and not usually so 
 distant, although in this latter feature they both differ very materially 
 among the different individuals, and the right valve is also distinctly 
 marked by the radii, which is not the case in that one. 
 
 Formation and locality. In calcareous clays of Jurassic age, ranging 
 about 20 feet above the red beds, at Red Water Valley, Black Hills, 
 Dakota. 
 
 2 B H 
 
18 
 
 FAM. MYTILDXffi. 
 
 GENUS MYTILUS, Li An. 
 
 MYTILUS WHITEI, n. sp. 
 
 Plate 5, figs. 9-12. 
 
 Shell of moderate size, trapezoidal in. outline, very oblique; hinge 
 line slightly arcuate, as long or a little longer than the distance from 
 the apex to the postero-basal extremity ; anterior or byssal border long, 
 distinctly concave from the apex of the beak to the junction of the basal 
 border, the general direction being at an angle of about 45, or within 
 45 with the cardinal line ; posterior margin a little more than half as 
 long as the shell and nearly parallel to the anterior border, or slightly 
 converging toward the base ; basal margin short and more or less 
 rounded, somewhat variable in different individuals. Beaks small, 
 pointed, terminal and incurved, with a short but distinct area-like 
 space beneath them; umbones prominent, subangular, and with a 
 slightly flattened or concave space on the anterior side, just below the 
 apex of the beak. Umbonal ridge elevated, strongly arcuate and sub- 
 angular, the -surface of the shell sloping rapidly to the posterior and 
 postero-cardinal margins. Anterior slope of the shell nearly or quite 
 vertical, or sometimes a little concave near the middle of the length. 
 
 Surface of the shell marked by numerous strong but very irregular 
 varices of growth, which give to the shell an extremely rugose appear- 
 ance. Bet ween the varices the surface is marked by fine lines of growth. 
 No radiating lines or other surface markings, beyond those described, 
 can be detected. Substance of the shell thick and strong. 
 
 The shell is a strongly marked and very characteristic species, and 
 judging from the fragments in the hand specimens of rock, must have 
 been an abundant form in a certain layer at the locality where collected. 
 We know of no American species of the genus having any close resem- 
 blance to this one. 
 
 Formation and locality. In rocks of Jurassic age, associated with 
 other Jurassic fossils, near Sun-Dance Hills, Northwestern Black Hills, 
 Wyoming. 
 
 GENUS TRAPEZIUM, Humph. (= CYPRICARDIA, Lam.}. 
 TRAPEZIUM BELLEFOURCHENSIS, n. sp . 
 
 Plate 5, figs. 1-4. 
 
 Shell small, transversely elongate-quadrangular, the length being 
 from two and a half to three times greater than the height ; dorsal and 
 basal margin subparallel, the former very slightly arched and the latter 
 scarcely concave, except in the older individuals, the smaller and me- 
 
19 
 
 (Hum-sized individuals being usually a little curved upward toward the 
 posterior end; beaks small, nearly terminal, rounded on the umbones 
 and very slightly incurved; posterior extremity truncate, in the older 
 specimens rather squarely so below, and rounding forward to the extrem- 
 ity of the hinge-line above. In the smaller individuals it is narrower, 
 somewhat sloping from above or obliquely truncate. Anterior end very 
 slightly prolonged below the middle of the height and excavated beneath 
 the beaks. A narrow linear escutcheon of considerable length is seen on 
 many of the separated valves. Anterior muscular impression rather 
 large and strongly impressed, as shown by the strong markings on 
 internal casts; posterior impression not distinguishable; pallia! line 
 faint, and the space within the limits often marked by radiating lines as 
 in the recent forms of the genus. 
 
 Surface of the valves veutricose, with a distinctly angular umbonal 
 slope in the larger specimen, but often obtusely rounded in the smaller 
 ones. A broad but rather faint depression runs obliquely backward 
 from the beak to the middle of the basal border on many individuals, 
 but is not always present. Surface of the shell marked by irregular 
 concentric lines of growth parallel to the margin of the valve. 
 
 The species is closely allied to a form described by Mr. Meek (in MS.) 
 under the name of Trepezium (Pachyniya) truncata, but is proportionally 
 very much more elongated than the specimens which are so labeled in 
 the collection at the Smithsonian Institution. The shells have been 
 exceedingly abundant in certain layers, being densely packed together, 
 so that it is impossible to separate the individuals. They are quite vari- 
 able in form at different stages of growth, the younger shells being 
 transversely elongate-ovate, narrowed and rounded, or very obliquely 
 truncate from above posteriorly, and becoming almost squarely truncate 
 behind in the older specimens, the slight sinuosity of the basal margin 
 being hardly noticeable until they attain to near their adult size. 
 
 Formation and locality. In a hard and somewhat siliceous limestone of 
 reddish color, at a level of 350 feet above the Triassic beds east of Belle 
 Fourche, Black Hills, Dakota. 
 
 TRAPEZIUM SUBEQUALIS, n. sp. 
 
 Plate 5, figs. 5-8. 
 
 Shell small, transversely elougate-subelliptical, about twice and a half 
 as long as high, or nearly so. Valves somewhat ventricose, wi:h large 
 tumid beaks situated a little nearest to the anterior end, and projecting 
 above the general line of the hinge; hinge-line, posterior to the beaks, 
 about half as long as the entire length of the shell, straight, but gradu- 
 ally declining to the extremity ; posterior end of the shell very obliquely 
 truncate, being much the longest below the middle of the postero-basal 
 angle ; anterior end shorter, slightly contracted in front of the beaks, 
 but rounded at the extremity and broader than the opposite end ; basal 
 
20 
 
 margin straight or very slightly convex in the middle, and strongly 
 rounded upward toward each extremity. Body of the shell often dis- 
 tinctly angular along the posterior-umbonal ridge and the postero-cardi- 
 nal slope quite abrupt ; some individuals, however, are obtusely rounded 
 on the'umbonal ridge. Surface of the shell marked by rather strong 
 concentric ridges of growth, which are crossed, on the rounded anterior 
 end and middle of the valve, by extremely fine radiating stripe, only 
 detected near the basal portion of the larger individuals by the aid of a 
 moderate magnifying power. 
 
 There may be some little doubt as to the true generic relations of this 
 shell, but it possesses so many of the features of Trapezium that we have 
 not hesitated to refer it to that genus ; the almost subcentral and some- 
 what prominent beak forms the strongest point of difference. It differs 
 in this respect from th e preceding species, as also in the general form 
 of the valves, and in the surface markings. The shells of the two 
 species have nearly the same dimensions, and in their mutilated and 
 imperfect condition, as seen imbedded in the rock, may readily be con- 
 founded, but the more prominent beaks and longer anterior end of this 
 one will at once distinguish them. 
 
 Formation and locality. In a hard white sandstone of Jurassic age, 
 associated with Pseudmonotis curta just above the Triassic red beds, at 
 Bed Canon Creek, Black Hills, Dakota. 
 
 Family uncertain.* 
 
 GENUS PLEUROMYA, Agassi*. 
 PLEUROMYA NEWTONI. 
 
 Plate 5, figs. 19 and 20. 
 
 Shell of moderate size, transversely subovate or triangularly ovate, 
 the greatest height being across the valve nearly on a line with the 
 beaks. Valves strongly convex near the anterior end, and in a cardi- 
 nal view acutely wedge-shaped, thickest opposite the beaks and rapidly 
 decreasing posteriorly. Beaks large, strong, enrolled, and approxi- 
 mate, situated at, or within, the anterior third of the shell and project- 
 ing largely above the the cardinal line. Hinge-line not exceeding one- 
 half the length of the shell, distinctly arched ; anterior end obliquely 
 subtruucate, longest below at its junction with the basal margin, and 
 in some cases the anterior slope is distinctly flattened. Posterior end 
 
 * The family relations of this shell, as well as some others herein described, are not 
 yet satisfactorily determined, and we do not like to refer them to a family to which 
 we feel certain, from their characters, as far as known, they have no resemblance or 
 affinity ; we rather prefer to leave them in doubt, and as subjects for future investiga- 
 tion. The reference of Pleuromya and Myacites to the same family with Anaiina we deem 
 unnatural, as from the character of the shell, and the consequent habits of the animal, 
 they must have been very far removed from each other in structural features, and 
 these we deem the ny sure and reliable means of classification. 
 
21 
 
 narrowed, the postero-cardinal margin rapidly declining from the ex- 
 tremity of the hinge-line to the longest point of the valve, which is 
 narrowly rounded and at about the middle of the height ; basal margin 
 very slightly constricted, or emarginate, just within the anterior third 
 of the length, by a faint sulcus, which passes from the surface of the 
 umbo to the base of the shell ; posterior to this it is strongly convex, 
 and as it approaches the posterior third of the length is more strongly 
 rounded upward to the extremity. Body of the valve convex, most 
 ventricose on the umboues and along the middle of the valve ; anterior 
 umbonal ridge obtusely angular; anterior slope abrupt and sometimes 
 flattened obliquely ; posterior umbonal ridge scarcely defined or broadly 
 rounded. Immediately behind the anterior umbonal ridge a broad 
 undefined sulcus passes across the valve, slightly modifying the direction 
 of the concentric lines. Xo appearance of escutcheon or lunule exists, 
 nor of an external ligament. 
 
 Surface of the shell marked by numerous irregular concentric undu- 
 lations, which are usually broad and undefined, but on some individuals 
 have a slightly sharper character. The general surface beyond these 
 undefined undulations appears to have been smooth, and we should 
 suppose from its character that it had been semipolished. Substance 
 of the shell moderately thick. The features of the hinge and interior 
 have not been fully ascertained ; there appears, however, on a left valve 
 a strong tooth-like process of considerable height, and in front of it a 
 deep triangular pit, probably ligamental. 
 
 This species differs from Myacites (Pleuromya) subcompressa, Meek 
 (Sixth An. Kept. U. S. Geol. Surv. Territories, 1872, p. 472), in being pro- 
 portionally longer ; more distinctly ovate or less triangular. The ante- 
 rior end being of greater length in proportion to the rest of the valve, 
 the beaks are larger and project farther above the cardinal line; 
 the body of the shell is less flattened and the surface less strongly 
 marked. 
 
 Formation and locality. In shaly limestone of Jurassic age, on top of 
 the highest hills two miles south of Belle Fourche, Black Hills, Dakota. 
 
 TA^CREDIA COEBULIFOMIS, n. sp. 
 
 Plate 6, figs. 5-8. 
 
 Shell small, seldom measuring more than half an inch in length, very 
 broadly ovate in outline and largest on the posterior side of the beaks, 
 the length being a little more than once and a half the height; the beaks 
 large and full, slightly enrolled, almost central and strongly inclined to- 
 ward the anterior part of the shell. Anterior end narrowed, strongly 
 constricted in front of the beaks, giving a somewhat concave antero- 
 cardinal line, the extremity acutely rounded; posterior end broadly 
 rounded, and the postero cardinal line convex to near the beaks ; basal 
 line regularly curved except at the posterior part where it becomes a 
 
22 
 
 little more abrupt. Body of the valve strongly convex, almost inflated 
 on the urnbo. 
 
 Surface of shell apparently smooth, but under a magnifier showing 
 faint, scarcely defined, lines of growth. 
 
 The species differs from T. inornata, M. & H., in its smaller size, more 
 inflated valves, proportionally larger and more prominent beaks, and 
 greater inequality in size of the anterior and posterior parts of the 
 shell. 
 
 Formation and locality. In sandy and somewhat shaly limestones 
 of Jurassic age, 350 feet above the red beds of the Triassic, east of 
 Belle Fourche, Black Hills, Dakota. 
 
 TANCREDIA BULBOSA, n. sp. 
 
 Plate 6, figs. 1-3. 
 
 Shell very small, the larger individuals not measuring more than three- 
 eighths of an inch in length, by a height of one-fourth of an inch ; very 
 broadly ovate in outline, being inflated and globuliform in the middle 
 and posteriorly, and attenuate, narrowed and compressed toward the 
 anterior extremity. Beak strong, inflated, curving anteriorly, and sit- 
 uated a little to the anterior of the middle of the shell ; anterior end 
 acutely rounded, the sides of the shell abruptly compressed by a broad, 
 undefined, constricting sulcus, or depression, which passes obliquely 
 across the valve from in front of the beaks to the basal border, in 
 which it forms a distinct emargiuation ; posterior end broadly rounded, 
 and the posterior cardinal line strongly convex; antero-cardinal line 
 constricted in front of the beaks, and concave between them and the 
 anterior extremity ; basal line very convex for a little more than two- 
 thirds of the length from the posterior end, where it becomes emargi- 
 nate at the base of the oblique sulcus or depression, which crosses the 
 anterior part of the valve. Surface semi-polished, and under a magni- 
 fier showing fine lines of growth. 
 
 The species resemble T. corbuliformis herein described, but is a smaller 
 shell, seldom occurring of more than half the usual length of that one, 
 and is much more extreme in the unequal size of the anterior and pos- 
 terior parts of the valve, besides being much more globose in form, and 
 having the anterior oblique sulcus of the valve much more strongly 
 marked. 
 
 Formation and locality. In rock of Jurassic age associated with T. 
 corbuliformis and T.inornata at the same locality. 
 
 TANCREDIA POSTICA, n. sp. 
 
 Plate 6, fig. 14. 
 
 Shell small, trausversly ovate, the height and length being about as 
 three to five. Valves very ventricose, becoming tumid near the beaks 
 and on the postero-cardinal part. Beaks large, and but little elevated 
 
23 
 
 above the cardinal line, slightly enrolled and directed forward, situated 
 at about one-third of the length from the anterior extremity; antero- 
 cardinal line abruptly declining in front of , the beaks to the middle of 
 the height of the valve ; anterior end narrow and sharply rounded ; 
 posterior end very broadly rounded, and the postero-cardinal and basal 
 margins subparallel behind the beaks, the extreme height of the shell 
 continuing to the posterior end; antero-basal line strongly curving 
 upward to the anterior end of the shell. Surface of the valves appar- 
 ently smooth. 
 
 The shell differs from any of the preceding species in the greater 
 length and proportionate size of the posterior portions of the shell, in 
 the situation of the beaks, and in their strong anterior inclination, the 
 others being much more erect than those of this species. It will be 
 readily recognized by the inflated valves, subparallel cardinal and basal 
 margins, and short anterior end. 
 
 Formation and locality. In shaly limestones of the Jurassic formation 
 east of Belle Fourche, Black Hills, Dakota, associated with the preced- 
 ing species. 
 
 FAM. V 
 
 GENUS DOSINIA, Scopoli. 
 
 DOSINIA JUEASSICA, H. sp. 
 Plate 5, figs. 21-24. 
 
 Shell of moderate size, subcircular or very slightly transverse in form, 
 and for the genus quite ventricose, with rather large, prominent beaks. 
 Cardinal line arcuate but less curved than the general circle of the 
 shell, while the anterior end is more sharply curved and slightly an- 
 gular, and the posterior portion from the extremity of the hinge to the 
 basal border very slightly flattened or truncate. Beaks anterior to the 
 middle of the valve, directed forward and approximate at their apices ; 
 lunule small and very slightly impressed ; ligament proportionally long, 
 but narrow, the shell at its margins slightly incurved. Body of the 
 valve ventrieose, most gibbous on the utnbones and below, while an- 
 teriorly and posteriorly the shell is more compressed ; umbonal ridges 
 not defined. 
 
 Surface of the shell smooth, with a few obsolete or faintly- marked 
 concentric irregularities, but no defined varices ; fine concentric lines of 
 growth are seen on the perfect shells under an ordinary magnifier. 
 Inner margins of the valves smooth ; muscular impressions large but 
 faintly marked, submarginal ; pallial line deeply sinuate, the apex of 
 the sinus being directed toward the beak of the shell. 
 
 The shell is a well-marked species of Dosinia so far as the characters 
 have been ascertained, but the hinge structure has not been seen, none 
 of the casts being in a condition to show the teeth. The casts are quite 
 
24 
 
 abundant on weathered specimens where they have apparently been 
 subject to the percolating action of mineral waters, which has partially 
 destroyed them. 
 
 Formation and locality. In Jurassic rocks at the top of the highest 
 hills, two miles south of Belle Fourche, and at a horizon of 350 feet 
 above the Triassic red beds, east of Belle Fourche ; and also on the east 
 side of Spear-fish Greek, near junction with the Ked Water, northeast 
 of Crow Peak, Black Hills, Dakota. 
 
 FAM. PSAMMOBinXE. 
 
 GENUS PSAMMOBIA, Lam. 
 
 . PSAMMOBIA ! PREMATURA, n. sp. 
 
 Plate 5, fig. 31. 
 
 Shell small, transversely elongated, with parallel dorsal and basal mar- 
 gins, the length equaling a little more than twice the height. Valves 
 very depressed-convex and distinctly gaping at each end. Beaks small 
 and inconspicuous, compressed, situated a trifle nearest the anterior end ; 
 the antero-cardiual line gradually declining with a very slight con- 
 vexity to the narrowly-rounded anterior end, basal margin straight for 
 more than half the length of the shell, rounding upward anteriorly and 
 posteriorly j postero-cardiual line a very little lower than the apex of 
 the beak, behind which it is straight to near th-e extremity of the shell ; 
 posterior extremity reaching its greatest length considerably above the 
 middle of the valve, the margin being directed obliquely forward below 
 to the end of the basal line. Surface of the valve regularly curved 
 from beak to base and from the posterior umbonal ridge forward to the 
 anterior extremity of the shell, forming nearly a level line; posterior 
 to the umbonal ridge the shell is depressed, forming a broad oblique 
 sulcus extending from behind the beaks to the posterior margin of the 
 shell. Muscular markings faint. Pallia! line not profoundly sinuate, 
 but distinctly emarginate behind. Hinge and teeth unknown. 
 
 The species is only recognized by single valves, but the form is so 
 precisely like that of some of the recent Psammobias that it seems 
 unnatural to refer it to any other genus. The parallel dorsal and basal 
 margins and the form of the posterior slope will readily distinguish it 
 from any other shell in the rocks from this region. 
 
 Formation and locality. In the sandy limestones of the Jurassic beds 
 east of Belle Fourche, Black Hills, Dakota. 
 
 GENUS NE^ERA, Gray. 
 NE^ERA LONGIROSTRA, n. sp. 
 
 Plate 5, fig. 35. 
 
 Shell very small, scarcely exceeding one fourth of an inch in length ; 
 transversely elongate-ovate or clavate, widest anterior to the middle, 
 
25 
 
 and narrowed behind, a little more than twice as long as high. Valves 
 very convex, becoming inflated near the middle and on the umbones. 
 Beaks proportionally large, erect, strongly projecting above the hinge 
 line, and situated in front of the middle of the length ; anterior end 
 large and broadly rounded, somewhat excavated beneath the beaks; 
 posterior end narrowed, elongate, and very slightly recurved, and ob- 
 liquely truncate above the umbonal angle; basal line strongly convex, 
 more distinctly so just in front of the middle opposite the beaks, and 
 broadly constricted behind ; posterior umbonal ridge very faintly an- 
 gular, and the cardinal slope rather abrupt. 
 
 Surface of the shell marked by a few concentric lines of growth, and 
 crossed on the anterior and middle parts of the shell by a few propor- 
 tionally strong, elevated, radiating ridges, to the number of eight or 
 nine, with wider flattened interspaces. 
 
 The species is small, and being preserved in a friable sandstone, the 
 surface characters are not clearly defined, nor can any of the hinge or 
 any other internal features be seen. 
 
 Formation and locality. In white sandstones of Jurassic age, in Red 
 Water Valley, Black Hills, Dakota: associated with Pseudomonotis 
 curta, Tancredia Warrenana, and other Jurassic fossils. 
 
 FAM. GASTROCILEXIim 
 
 GENUS SAXICAVA, Bettevue. 
 SAXICAVA JURASSICA, n. sp. 
 
 Plate 5, figs. 25-30. 
 
 Shell small, elougate-subcylindrical, with subparallel dorsal and basal 
 margins ; beaks approximate, distinct, situated near the anterior end 
 and flattened on the exterior surface ; umbonal ridge strongly marked 
 and subangular, placed behind the middle of the valve. Anterior end 
 narrowed and very slightly excavated below the beaks ; posterior ex- 
 tremity wider and rounded on the margin, the sides being laterally com- 
 pressed ; basal margin very gently concave in the middle of its length. 
 Body of the valves very broadly sulcated between the anterior end and 
 the umboual ridge, and somewhat inflated along the latter feature pos- 
 terior to the middle of the length. Surface of the shell rather distinctly 
 marked by concentric lines parallel to the margin, which are elevated 
 and irregular, but not lamellose ; also by a few strong undulations of 
 growth. Just below the hinge-line, on the postero-cardinal border, the 
 surface strke are slightly bent and the surface of the shell very slightly 
 angular. Internally, as seen on casts, the anterior muscular impression 
 is narrow, and situated along the antero-basal margin. The pallial line 
 appears to be strongly sinuate, and the dorsal margin shows evidence of 
 a rather strong ligament. The casts of the burrows, as seen in the rock, 
 are almond shaped, or very elongate-ovate. 
 
26 
 
 A small fragment of argillaceous rock in the collection was found to 
 contain quite a number of the burrows, and, on being broken, a few 
 were found with the shells in position ; but in an effort to develop them 
 from the matrix, the shell is usually removed from the casts, although, 
 some of it is at times retained, and it is from this rather imperfect ma- 
 terial that the description has been drawn. The general form of the 
 shell and also the external texture would seem to ally them with the an- 
 gular group of the genus Lithodomus, characterized by L. gruneri Phil- 
 lipi, but the sinus of the pallial line would seem to forbid this reference. 
 
 Formation and locality. In rocks of Jurassic age, at a horizon of 350 
 feet above the red beds of the Triassic, at Red Water Valley, Black 
 Hills, Dakota. 
 
FOSSILS OF THE CRETACEOUS. 
 
 27 
 
MOLLUSCA. 
 
 LAMELLIBEANCHIATA. 
 
 FAM. PTERIID^], Meek. 
 
 GENUS PTERIA, Scop. 
 PTERIA (PSEUDOPTERIA) SUBLEVIS, n. sp. 
 
 Plate 7, fig. 6. 
 
 Shell small, erect, sub-rhomboid or sub-ovate in outline, left valve 
 depressed-convex, most ventricose on the umbo and toward the beak, 
 near which it becomes subangular. Hinge line shorter than the length of 
 the shell below, and about two-fifths as long as the height ; anterior wing 
 minute, obtusely pointed, posterior wing moderate in size and convex, 
 scarcely separated from the body of the shell by a slight almost imper- 
 ceptibly depressed line ; anterior side of the shell gradually receding 
 from below the anterior wing to the basal border, which is rather 
 sharply rounded, and the postero -basal margin a little more sharply 
 rounded than the basal. 
 
 The surface of the valve in all the specimens seen is much exfoliated, 
 so that the surface features are not positively known, but it has, appar- 
 ently, been quite smooth. The substance of the shell remaining on the 
 specimens is highly nacreous. 
 
 Several individuals of the left valve have been noticed in the collec- 
 tion, but none of the right have been recognized. Those seen all have 
 the same character, and one of about the same size, being a little less 
 than three-fourths of an inch in length by about half an inch in width. 
 It most nearly resembles in form P. (Pseudopteria) fibrosa, M. & H. 
 (Paleont, U. S. Geol. Surv. Territ, p. 36, pi. 17, fig. 17), but differs en- 
 tirely in the surface features, being entirely destitute of the faint plica- 
 tion of that species. 
 
 Formation and locality. In limestone of Cretaceous age, ]N~o. 4, Old 
 Woman's Fork, Black Hills, Dakota. 
 
 Among the collections from the Fort Pierre group there are large 
 numbers of Inocerami, representing several of the species and varieties 
 recognized by Mr. F. B. Meek, in his excellent work on the Upper Mis- 
 souri Cretaceous formations, just issued by the Department of the In- 
 terior. But notwithstanding the careful manner in which these forms 
 have been described and figured by that author, we find great difficulty 
 
 29 
 
30 
 
 in arriving at any very satisfactory conclusions as to the limits of species 
 when so large a collection is examined. The species, as figured in the 
 above-mentioned work, appear distinct enough, and the lines of demarka* 
 tion well drawn, when a few individuals only are before one, but among 
 the collections in hand we find the boundaries crossed in every direc- 
 tion, so that we are at a loss in many cases for characters by which to 
 separate the different forms there indicated, while there are still others 
 among them so entirely different from any of those described and fig- 
 ured that we are very reluctantly compelled to consider them as entirely 
 distinct. 
 
 Among the forms representing those given under the names J. 
 Vaunxemi, I. proximus, and I. proximus, var. subcircularls, and also 
 as 1. convexus and J. Sagensis, var. Nebrascensis and I. Balchii, we find 
 such gradually connecting links as to make it extremely difficult if not 
 impossible to draw lines of distinction between them. Again, those re- 
 sembling the forms given under the names I. Cripsiij var. Barabini and 
 J. tennilineatus, are similarly united. 
 
 The forms which we had referred to I. Sagensis and 1. Nebrascensis 
 of Owen, vary so greatly in the posterior prolongation of the shell and 
 also in the direction of the basal margin as to defy all attempts to class- 
 ify them by their form, and in the relative degree of convexity and the 
 comparative distance of the surface undulations they are eqally variable 
 and unsatisfactory. We find also that the relative projection of the 
 beaks and the width of the cartilage area r as well as the distance of the 
 beaks from the anterior end, is subject to great variation. Although 
 in the collection before us there are but few individuals which retain 
 the right and left valves in contact, still of many of them we have both 
 valves of similar size and form from the same locality, and we find that 
 the difference in convexity between the two valves is not, in any case, 
 very great, and often scarcely perceptible. The beak of the left valve 
 is usually larger and projects more beyond the line of the hinge than 
 that of the right, and the cartilage area is a little wider. Perhaps if the 
 real surface features of the shells were preserved on the specimens 
 more reliable characters for specific distinction might be presented, 
 but the fibrous coating is almost always absent, being generally left in 
 the matrix and not collected, or perhaps in many cases removed by 
 some action of decay before the shells are finally imbedded in the rocky 
 sediment, so that in collections it is seldom that any part of this layer 
 is retained on the specimens, except a little around the beaks or along 
 the hinge margins. Owing to these difficulties, the same that Mr. Meek 
 has found to exist among his specimens, and also to the impossibility of 
 giving a sufficient number of figures to show fully and clearly the vari- 
 ations which we have found among the examples in hand, we shall be 
 obliged to follow very nearly the same specific limits which that author 
 has found desirable, though we must confess that in some cases we 
 should prefer rather to consider some of the forms found associated to- 
 
31 
 
 gether in the same localities and presenting only slight differences, as 
 one and the same species, than to identify these far western forms with 
 species described from Europe, as has been done by so many authors. 
 We do not dispute their great resemblances, but believe them to be 
 rather representative species than equivalent forms. 
 
 INOCERAMUS PERPLEXUS, n. sp. 
 
 Plate 8, fig. 3, and plate 10, figs. 4 and 5. 
 
 Shell rather below the medium size, erect, truncate, subovate in out- 
 line, shortest at the hinge-line, and gradually expanding to below the 
 middle of the height ; valves convex ; beaks terminal, slightly inclined 
 forward, pointed, and incurved ; hinge-line short and straight, not 
 exceeding two-thirds of the length below in any of the examples seen ; 
 anterior border straight or very slightly concave for more than half the 
 height of the shell, where it unites with the deeply rounded basal 
 border; posterior margin of the shell gradually widening from the 
 extremity of the hinge-line to the point of greatest width, in an antero- 
 posterior direction, which is rather below the middle of the height, 
 where it unites in a regular curve with the basal margin. Valves most 
 strongly convex along the umbonal ridge, which is situated nearest to 
 the anterior side of the shell and slopes gradually to the postero- 
 cardinal portion, where it becomes almost flattened ; while the anterior 
 border is vertical, or sometimes slightly concave, for more than half the 
 depth of the valve. 
 
 {Surface of the shell marked by strong, irregular, concentric folds or 
 undulations, parallel to the margin and passing off on the vertical 
 anterior border. Substance of the inner layers highly nacreous. Fibrous 
 coating, when preserved, apparently thin. 
 
 This species is somewhat remarkable for its erect form and strong 
 concentric undulations. In form it resembles the specimens of I. fragilis 
 Hall and Meek, given by the latter author, (Pal. U. S. Geol. Surv. 
 Territ,, p. 42, figs. 1 2), but in the surface characters it is entirely dis- 
 tinct from that species, and, when compared with examples of that 
 species having the characters of the original specimen, is very readily 
 distinguished. It also somewhat resembles I. JSllioti Gabb from the 
 Cretaceous sandstones of San Francisco Harbor, Gal. 
 
 Formation and locality. In concretionary limestone at the top of 
 shales of Cretaceous Xo. 2, on the Belle Fourche, about ten miles west 
 of Crow Peak, Black Hills, Dakota. 
 
 ENDOCOSTEA, new gen. 
 
 Shell resembling Inoceramus, being bivalve, with both sides convex, 
 but more or less unequal, and composed of two layers, an outer verti- 
 cally fibrous coating and an inner nacerous or pearly lining ; hinge-line 
 straight, edentalous, with a narrow linear external cartilage area on 
 
32 
 
 each valve. Yalves provided with an oblique internal rib, passing from 
 behind the beaks, along the postero-cardinal slope, toward the postero- 
 basal margin, marking the position of the posterior muscular imprint. 
 Other muscular marking unknown. Type, = E. Typica, Whitf. 
 
 We have not been able to detect the anterior muscular scar or pallial 
 line, except the latter as an irregular transverse line of small tubercles 
 across the beak of internal casts in several cases, and a slight, curving 
 ridge, faintly marked on a smaller number of examples, passing from 
 the apex along the anterior side for a short distance. The genus differs 
 from Inoceramus, so far as yet known, only in the existence of the 
 internal rib. The species now known are E. alveatus = Inocemmus alve- 
 atuSj Morton ; E. impressus = I. impressus, D'Orb. ; E. sulcatus = I. cripsii 
 var. Sulcatus, Eoemer ; and E. typica, Whitf., herein described. 
 
 ENDOCOSTEA TYPICA, n. sp. 
 
 Plate 9, figs. 1-7. 
 
 Shell of medium size, transversely subovate, oblique, and slightly ine- 
 quivalve, the right side being the largest in the only example where 
 they are preserved in contact. Valves strongly ventricose at the ante, 
 rior end and on the anterior part of the umbonal region, becoming more 
 compressed and attenuate behind and along the posterior cardinal por- 
 tion, sometimes strongly depressed and concave between the cardinal 
 line and dorsal slope. Hinge-line straight, often two-thirds as long as 
 the shell below, and slightly rounded at the extremity. Beaks small, 
 incurved, projecting but little above the cardinal line, and situated near 
 the anterior end, but not quite terminal. Anterior end short, sharply 
 rounded at the antero-cardinal angle, and extending a little forward 
 below for about half the height of the valve, when it rounds backward 
 to the basal line, the upper part forming, with the cardinal line, an angle 
 of about 95 to 100. Posterior end nearly equal to, or narrower than, 
 the anterior, and more sharply rounded, most strongly from below. 
 Basal line forming nearly half of an ellipse, or semiovate, the widest 
 part varying from in front of to behind the middle of the length, in 
 different individuals. Surface of the valves usually marked by very 
 distinct concentric undulations, though sometimes they are only moder- 
 ately developed. Oblique internal rib strongly marked, narrow and 
 pointed near the beak, and gradually widening and deepening posteri- 
 orly, the concentric furrows distinctly crossing and leaving, on the 
 deeply concave channel of the casts, corresponding depressions. Inner 
 layers of the shell highly nacreous ; outer prismatic layer very thin. 
 
 This species resembles Inoceramus Barabini, as it is recognized in the 
 same region, in the general form and in the subcuneate anterior end of 
 the shell; but the concentric furrows are generally more distinctly 
 marked and regular. It is readily distinguished by the oblique sulcus 
 and by the opposite valve being the largest, if the example above refer- 
 red to, and figured on the plate, is rightly interpreted. 
 
33 
 
 We have great doubts of tbe identity of the western forms with I. 
 BaraUni Morton, from Alabama, and are inclined to believe they would 
 be more naturally classed under a distinct name, as formerly done by 
 Messrs. Meek & Hayden. 
 
 Formation awl locality. In limestone of the Fort Pierre group, at Old 
 Woman's Fork of the Cheyenne River, Black Hills, Dakota, where they 
 occur very abundantly, densely packed together in the rock, and pos- 
 sessing the specific characters and the oblique sulcus in a remarkably 
 constant degree. 
 
 MCULASID^E. 
 Genus NUCULANA. 
 
 XUCULANA SUBEQUILATERA, 11. Sp. 
 * Plate 11, figs. 3 and 4. 
 
 Shell of small size, transversly elongate-subovate, with large, promi- 
 nent, suberect beaks which are placed a little in advance of the middle 
 of the length, and are slightly incurved, but comparatively distant. 
 Valves convex, as seen on the casts, ventricose in the middle and below 
 the beaks, and compressed toward the extremities ; more particularly 
 so posteriorly ; hinge-line abruptly bent between the beaks, the opposite 
 sides forming an angle of about 140, the posterior side slightly recur- 
 ring in the outer part ; anterior end of the shell sharply rounded ; pos- 
 terior extremity acutely rounded near the extremity of the cardinal line, 
 and rapidly sloping forward below to the basal margin, which is broadly 
 curved and almost straightened in the middle. 
 
 Surface of the shell unknown ; hinge-plate marked by a large num- 
 ber of comparatively long, slender teeth, minute in the middle, and 
 gradually increasing in size and length outwardly ; about twenty may, 
 with difficulty, be counted on the posterior side of the beaks, and about 
 eighteen on the shorter side. Cartilage pit small ; muscular imprints 
 faintly marked. Xo sinus can be detected in the pallial line. 
 
 The species seems to be nearly related to Nucula (Nuculanaf) equilat- 
 eralis, M. & H., but the beaks are not central as in that species, but 
 are situated at about two-fifths of the length from the anterior end, and 
 the teeth are decidedly not obtuse, but on the contrary are very slender, 
 as seen on the casts. 
 
 Formation and locality. In Cretaceous rocks on the Cheyenne Itiver, 
 near French creek ; supposed to be very near the top of the Fort Pierre' 
 group. 
 
 3 B H 
 
34 
 
 FAM. CRASSATELLIDJE. 
 GENUS CRASSATELLA, Lam. 
 CRASSATELLA SUBQUADRATA, n. sp. 
 
 Plate 11, fig. 12. 
 
 Shell small, subquadrangular in outline, with thin, compressed valves 
 and not prominent beaks, which are situated within the anterior third 
 of the length ; length of the shell exceeding the height ; basal margin 
 broadly rounded ; anterior end short and narrowly rounded ; posterior 
 end broad and rounded truncate ; posterior hinge-line straight and sub- 
 parallel to the basal margin. Surface of the shell unknown. Muscular 
 impressions small; the posterior one situated close beneath the extremity 
 of the hinge-margin, and the anterior scar subinarginal. Pallia! line 
 not distinctly marked; margin of the valves crenulate. 
 
 The only specimen of this genus recognized among the collections 
 from the Black Hills is a small internal cast, answering to the above 
 description, and apparently a true Orassatella. Although the extremity 
 of the hinge-plate has not been seen, the cast has all the features usually 
 possessed by casts of the typical forms of the genus. 
 
 Formation and locality. In Cretacous beds on the Cheyenne River ; 
 probably from the Fort Pierre' group. 
 
 CTPEINID^E. 
 
 GENUS SPILERIOLA. 
 SPH^ERIOLA TRANSVERSA, n. sp. 
 
 Plate 10, figs. 14-16. 
 
 Shell of rather large size, subsphaeroidal, a little transverse, or longer 
 than high, exclusive of the projection of the beaks, the outline of the 
 margin of the valve being slightly oblate or transversely broad-oval, and 
 nearly symmetrical. Valves highly inflated on the central area and 
 umbones, with strong, highly-elevated, strongly-incurved, subcentral 
 beaks, which are slightly curved forward and subangular on the um- 
 bonal ridges. 
 
 Surface of the shell marked by sublamellose, concentric lines of growth , 
 which form strong distant undulations in some cases toward the ex- 
 tremities of the shell. 
 
 Internally the muscular impressions are large and subcircular, and 
 the pallial line simple and entire. The cardinal teeth, as obtained by a 
 gutta-percha mold from a natural cast, consist of two tuberculiform 
 teeth beneath the beak, and the laterals are represented by a strong 
 oblique fold or ridge passing from near the beak to within a short dis- 
 
35 
 
 tance of the posterior border of the hinge-plate, where it is marked or 
 divided by au impressed pit, which may be accidental. 
 
 Compared with S. obliquata Meek, this shell is more equilateral, the 
 beaks more nearly central, and the shell less oblique. It differs from 
 S. Moreanenris of the same author in having much larger beaks, more 
 strongly enrolled, and the shell is also more transverse. 
 
 Formation and locality. In ferruginous sandstone of Cretaceous Xo.5. 
 On Che Cheyenne River, near Old Woman's Fork, Dakota. 
 
 ZELLINIDJ^. 
 
 GENUS LIOPISTHA, Meek 
 
 SUBMENUS CYMELLA, Meek-. 
 
 LEIOPISTHA (CYMELLA) MEEKI, n. sp. 
 
 Plate 11, figs. 27 and 23. 
 
 Shell of moderately large size, transversely oval in outline, about once 
 and a half as long as high. Valves very convex, with large, tumid, in- 
 curved beaks, which are located a little more than one-third of the entire 
 length from the anterior end of the shell, and are considerably elevated 
 above the cardinal line ; anterior and posterior ends of the valve broadly 
 and nearly equally rounded, and the basal line between the longest 
 points of the shell forming a very regular and nearly symmetrical semi- 
 oval curve ; cardinal line sloping gradually on both sides of the beak, 
 the anterior side marked by a narrow, lanceolate, lunule-like depression, 
 and the posterior side by a larger, broader area, bordered by an elevated 
 ridge. Concentric undulations of the surface strong and distinct, con- 
 tinuing their sharpness to the margins of the cardinal depressions, and 
 gradually increasing in strength with the increased size of the shell to 
 below the middle, beyond which point they become flattened and fainter ; 
 about twenty-seven may be counted on the entire surface. The concentric 
 undulations are crossed by comparatively strong radiating cost, which 
 do not mark the depressions between the undulations, but exist only on 
 their flattened surfaces. The radii are strongest on the central parts of 
 the shell and become gradually finer and closer toward the lateral ex- 
 tremities, and are visible on the anterior end to the margin of the car- 
 dinal depression, but on the posterior end are not seen to exist quite so 
 far. The crests of the radii appear to have been marked by a row of 
 minute puncta, seen only under a magnifier, three and four existing to 
 each undulation. The surface of the shell is also marked by fine, some- 
 what wrinkled, concentric lines of growth, especially on the larger parts 
 of the valve, but apparently confined to the outer coating of the shell, 
 and presenting the appearance of a thick epidermis. 
 
 We were at first inclined to consider this as P. umlulata M. & H., but 
 on strict comparison with Mr. Meek's description in the Pal. of the U. S. 
 
36 
 
 Geol. Surv. Territ., which we have just received, have concluded it to 
 be a different species. It differs, first, in the greater size and more 
 robust habits, also in the comparatively stronger undulations, and in 
 having the radiating costse continuing to the anterior end if not to the 
 posterior also. The outline of the shell also differs somewhat. 
 
 Formation and locality. In Cretaceous strata at Dead Man's Rapids, 
 Upper Missouri. Probably of No. 5. 
 
 FAM. AXATINID J]. 
 
 GENUS THRACIA, Leach. 
 THRACIA SUBGRACILIS, n. sp. 
 
 Plate 11, figs. 29 and 30. 
 
 Shell small, transversely ovate and slightly iuequivalve, valves con- 
 vex, veutricose in the middle, but becoming quite compressed and al- 
 most constricted behind ; anterior part large, forming nearly or quite 
 four-fifths of the entire bulk of the shell, the extremity rounded ; basal 
 line full in front of the beaks and constricted or sinuate behind ; posterior 
 end narrow and subtruncate ; anterior cardinal line long, nearly on a 
 line with the beaks and very slightly convex ; posterior to the beaks 
 the cardinal line is constricted and narrowed $ beaks small and com- 
 pressed, appearing as if directed backward. 
 
 The surface of the only specimen is imperfect, the shell being in great 
 part removed, but where preserved is marked by concentric lines of con- 
 siderable strength, approaching in character to undulations rather than 
 striae. The beaks are small and marked along their apices, and for a 
 short distance below, by a slight notch or slit, from the removal of a 
 narrow ridge which has marked the interior of the shell, as in Anatina, 
 and supporting the cartilage-pit. The shell, in its external form, has 
 all the features of Thracia, being slightly inequivalve and also slightly 
 twisted when viewed in profile, and also in the character of the surface 
 markings. The muscular impressions or pallial line cannot be distin- 
 guished through the remaining shell, and we are therefore in doubt con- 
 cerning these features. It bears considerable resemblance to Thraqia 
 gracilis M. & H. (Pal. U. S. Geol. Surv. Territ., p. 224, PI. 30, fig. 6), 
 but is proportionally shorter and somewhat more contracted in height 
 posteriorly. 
 
 Formation and locality. In Cretaceous rocks, probably near the top 
 of No. 4; near French Creek, on the Cheyenne River, Dakota. 
 
37 
 
 GASTEROPODA. 
 
 FUSUS CHEYENNENSIS, n. 8p. 
 
 Plate 12, fig. 9. 
 
 Shell small, spire slender and elevated, the number of volutions un- 
 known, but probably six or more, strongly rounded, the last one some- 
 what ventricose above the middle but attenuate below ; aperture semi- 
 ovate, being rather straightened on the inner side and slightly produced 
 below. Volutions crossed by numerous vertical folds or plica?, which 
 are very slightly bent backward in their course across the volution. 
 Surface of the shell unknown. 
 
 The specimen from which the description is drawn is an internal cast, 
 and therefore the external characters cannot be given in detail. The 
 species is, however, so entirely distinct from any of the forms known 
 from this region, that there is no fear of its being confounded with any 
 of them. 
 
 Formation and locality. In the gray shales near the upper part of the 
 Fort Pierre group. On the Cheyenne River, near Rapid Creek, Black 
 Hills, Dakota. 
 
 APORRHAI^ MEEKI, n. sp. 
 
 Plate 12, fig. 5. 
 
 Shell of moderate size, with a low, very obtusely pointed spire, which 
 is composed of only three ventricose or rounded volutions, exclusive of 
 the apertural expansion, and which rapidly increase in size ; apical angle 
 nearly eighty degrees. Volutions marked by numerous sharply elevated 
 revolving lines, with concave interspaces both above and below the 
 middle. Outer lip expanded, and extended into two diverging carinated 
 digitations of an undetermined length, which are deeply grooved on the 
 inner face, the upper one being directed slightly backward toward the 
 spire, and the other one slightly downward and more strongly forward 
 in the direction of the coil of the shell ; anterior beak, judging from the 
 part remaining, moderately long and stout ; posterior canal extending 
 along the spine to the summit, where it appears to have become free 
 and deflected ; callous slight(?), coating the upper volutions over a part 
 of their extent. 
 
 This species differs from any previously described form of this group, 
 in the short obtuse spire, combined with the two digitations of the outer 
 lip, and the posterior canal which extends to the summit of the spire. 
 
 Formation and locality. In limestone of the Fort Pierre group, at the 
 top of the gray shales of this formation. On the Cheyenne River, near 
 Rapid Creek, Black Hills, Dakota. 
 
38 
 APORRHAIS (G-ONIOCHEILA) CASTORENSIS, n. sp. 
 
 Plate 12, fig. 1. 
 
 Shell small, with a moderately elevated spire, composed of about four 
 flattened or very slightly veutricose volutions, which are crossed by fine 
 flexuous, vertical folds, strongly directed forward in their course across 
 the whorl, and also marked by fine thread-like revolving lines ; suture 
 distinct; apical angle about 40, but slightly variable on different 
 individuals. Body volution proportionally large and very strongly 
 angular, or even carinate, along the middle, flattened or sMghtly concave 
 on the upper surface and rapidly contracted below to the short, pointed 
 rostral beak. A second rather indistinct carination marks the surface 
 a little below the first, but seldom or never extends to the margin of the 
 lip. Outer lip expanded, strongly carinate on the back and projecting 
 in the middle, to form a short, obtuse, slightly recurved digitation, and 
 posteriorly extending along the spire to the base of the second volution 
 above. 
 
 This species somewhat resembles A. biangulata, M. & H. (Pal. U. S. 
 Geol. Surv. Territ., p. 322, pi. 19, fig. 6), but differs in the subdued 
 character of the lower carination and in the strongly uuiaugular form of 
 the body volution. Among a number of specimens none show the pos- 
 terior canal extending above the point described, nor any evidence of a 
 second digitation to the lip. The surface markings are quite superficial, 
 but few specimens showing them, appearing quite smooth from slight 
 exfoliation. 
 
 We are extremely averse to describing new species of this group of 
 shells, as, from their extreme liability to variation with different degrees 
 of development, they are easily mistaken ; and we have feared that this 
 might prove, on the examination of a larger and better collection of 
 specimens, to be only a form of A. Uangulata, M. & H., above referred 
 to; but the single strong carination, and the fact that it comes from a 
 lower geological horizon and distant locality, have induced us to separ- 
 ate it under a new name. 
 
 Formation and locality. In a ferruginous sandy limestone, on the 
 East Fork of Beaver Creek, Black Hills. Associated with fossils of the 
 Fort Beuton group. 
 
 GEXUS AKKRA, 0. F. Muller. 
 
 AKERA GLANS-ORYZA, n. sp. 
 
 
 
 Plate 12, fig. 25. 
 
 Shell minute, not exceeding one-fifth of an inch in length, and the 
 diameter being about twice and a half less than the length ; cylindrical 
 in form, with a very low, truncated spire, which consists of about three 
 or three and a half volutions, the outer margins of which are bordered 
 
39 
 
 by ail elevated kiiife-edge carina, giving a deeply channeled convolute 
 character to the spire, the center scarcely rising above the level of the 
 outer carination. Body of the outer volution very slightly rounded near 
 the margin of the flattened spire, and distinctly so to the base below. 
 Aperture as long as the shell, narrow above and gradually widening and 
 rounded at the base. Columella curved and apparently reflected upon 
 the preceding volution. Axis imperforate. 
 
 Surface of the shell marked by very fine, revolving, impressed lines, 
 strongest near the top of the volution and on the lower third ; also by 
 finer transverse striae of growth, parallel to the margin of the aperture, 
 and indicating by their direction that the central portion of the outer 
 lip is a little in advance of the top and base. 
 
 Formation and locality. In limestone, near the top of the Fort Pierre 
 group. On the Cheyenne River, near French Creek, Black Hills, Dakota. 
 
 CEPHALOPODA. 
 
 GEXCS HELICOCERAS, VOrb. 
 
 HELICOCERAS STEVENSONI, n. sp. 
 
 Plate 14, figs. 4-7. 
 
 Shell large and robust, with an elevated, moderately tapering spire, 
 which is composed of strong, cylindrical, disconnected, dextrally coiled 
 volutions, sharply enrolled *and leaving an umbilical opening equal to, 
 or a little greater than, one-half the diameter of the volution encircling 
 it. The volutions are at first widely disconnected and rapidly descend- 
 ing, but become more closely coiled below, and in the lower part of the 
 example figured are but slightly disconnected. 
 
 Surface of the shell marked by strong, rounded, annulatiug costa, 
 passing entirely around the shell, and separated by wider concave inter- 
 spaces. On the upper surface of the volution the costa are strongly 
 directed backward, but are recurved, and on the outer face are directed 
 gently forward below and within the umbilicus. The costa are farther 
 ornamented by two irregular rows of strong, obliquely-rounded, tuber - 
 culose nodes, the upper range being situated along the middle of the 
 volution, and the other half-way between it and the center of the basal 
 surface. The nodes of the two ranges, although usually placed on the 
 same costa, are not constantly so, but frequently alternate, and in very 
 many cases two of the costa unite at the lower node, continuing only 
 as one on the lower side of the volution. 
 
 Septa rather distantly arranged, leaving considerable space between 
 them, the convolutions of a single septum occupying a space on the 
 periphery of the shell, equal to from two-thirds to three-fourths of the 
 diameter of the volution, at the point examined. Siphonal lobe longer 
 than wide, and deeply divided at the extremity into two principal 
 branches, each of which are again deeply divided, and the divisions 
 
40 
 
 furnished with numerous serrated digitations. First lateral lobe very 
 large and unequally divided into two principal branches, the outer one 
 of which is the largest, and each is again divided and furnished with 
 numerous compound digitations. The second lateral lobe is much 
 smaller than the first, and similarly divided, but the divisions are smaller 
 and less complicated. (The inner half of this lobe has not been distinctly 
 traced.) First lateral sinus rather large and deeply cleft in the middle 
 by an auxiliary lobe, the lower end of which is divided into several digi- 
 tations. Second lateral sinus shorter and comparatively more spreading 
 than the first also, and deeply divided in the middle by a simple auxili- 
 ary lobe having four spurs on each side. Other lobes and sinuses not 
 observed. Siphuncle rather small, marginal, and passing along the mid- 
 dle of the volution. 
 
 This species would appear, without critical examination, to be some- 
 what closely related to Heteroceras f angulatum, M. & H. (Pal. U. S. Geol- 
 Surv. Ten-it., p. 484, pi. 21, fig. 3), more especially as their species is 
 stated to be "(dextral?)"; and their figures, being placed base upward, 
 which may be seen by the position of the nodes, are liable to mislead, 
 but if critically examined will be found, from the direction of the costa, 
 to belong to a sinistral shell, as they incline in an opposite direction to 
 those of a dextral shell. Mr. Meek states loc. cite that the fragment 
 figured is supposed to be from the deflected part of the shell, and for 
 this reason is placed provisionally, with doubt, under the genus Hetero- 
 ceras. It is, perhaps, impossible for one to feel positive that a shell of 
 this group has not been, or would not be, deflected at some period of 
 growth, unless a perfect adult individual is obtained. Our shell figured 
 shows no evidence whatever of any tendency to become deflected ; still 
 it is known to be imperfect, as it is septate to within an inch of the 
 outer extremity, and we cannot therefore feel positive of its true generic 
 relations. The upper part of the spire has, however, been very loosely 
 coiled, or widely disconnected, becoming more compact with increased 
 growth 5 in this respect being the reverse of shells belonging to the genus 
 Heteroceras. Owing to this feature, and the absence of any evidence of 
 the generically-required deflection in the adult stages, we have con- 
 sidered it most natural to refer it to Helicoceras. 
 
 Formation and locality. In limestone of the Fort Pierre group, on 
 the west side of Beaver Creek, southwest Black Hills. 
 
 GENUS HETEROCERAS, D'Orb. 
 HETEROCERAS NEWTONI, n. sp. 
 
 Plate 15, figs. 1-4. 
 
 Shell dextral, of moderate size, composed of from two and a half to 
 three, loosely coiled, disconnected, and rather rapidly increasing 
 volutions forming the rather low but somewhat rapidly spreading 
 
41 
 
 > 
 
 spire, below which point the shell is deflected to an unknown extent. 
 Transverse section of the shell circular, or nearly so. Umbilicus very 
 wide in the upper part of the spire, but scarcely increasing in diameter 
 with the increased growth of the shell above the deflected portion, the 
 increased diameter of the tube about equaling the increased diameter 
 of the whorl. 
 
 Surface of the shell ornamented by low, subangular, transverse ridges 
 or costa, which pass entirely around the shell and are separated by 
 wider concave interspaces ; also by two longitudinal rows of obliquely 
 rounded nodes, the upper one of which is placed at, or just below, the 
 periphery, and the other at about one-eighth of the circumference of 
 the tube below the first, and on the line of the same ridge with it. 
 Transverse costa arranged in sets of three 5 two of each set coalescing 
 to form the oblique nodes, the third one passing around the tube, without 
 interruption, midway between the two adjacent pairs of nodes. The 
 direction of the costa is strongly backward on the upper inner surface 
 of the volution, then recurving and passing obliquely forward in cross- 
 ing the outer face of the shell from above to the base, and also within 
 the umbilicus. Siphuncle small, marginal, situated as far above the 
 upper line of nodes as the distance between the two lines. 
 
 Septa approximate, the extremities of the lobes of one slightly inter- 
 fering with those of the saddles of the next adjacent, but not interlock- 
 ing ; the space occupied by the convolutions of the lobes and sinuses of 
 a septum is equal to three-fifths of the diameter of the tube at the 
 position of the septum measured ; the ramifications of the lobes are 
 sharply angular and pointed. The siphonal lobe is longer than wide,, 
 deeply divided at the extremity into two rather long, compound digitate 
 processes, and a short median bifid process. First lateral lobe very 
 deeply and unequally divided and the branches widely spreading,, 
 and deeply serrate-digitate. Second lateral lobe very much smaller than 
 the first and less spreading. Antisiphonal lobe single, longer than wide, 
 deeply digitate on the side and divided into four small, unequal digita- 
 tions at the extremity. Sinuses large, spreading, and deeply cleft by 
 auxiliary or secondary lobes. 
 
 The type specimen of the species is imperfect, but preserves one and 
 one-third volutions ; the volutions are entirely disconnected and increase 
 rapidly in size, while the umbilicus retains the same diameter, the upper 
 volutions appearing to have been not more closely coiled than those 
 preserved. The outer extremity of the specimen retains a part of the 
 deflected portion which is bent downward as well as outward, and is 
 septate nearly to the end. The species appears to be related to H. f 
 Nebracensis, M. & H., Pal. U. S. Geol. Surv. Territ., p. 480, pi. 22, fig. 1, 
 a, &, o, but differs, however, in the more rapidly increasing volutions ; 
 in the disconnected whorls ; simple costa (i. e., not bifurcating) ; in the 
 position of the siphuncle, and in the details of the lobes and sinuses. 
 
 Formation and locality. In limestones of the Fort Pierre" group, on the 
 west side of Beaver Creek, southwest Black Hills. 
 
42 
 
 GENUS ANCYLOCERAS, D'0r&. 
 ANCYLOCERAS JENNEYI, n. sp. 
 
 Plate 16, figs. 6-8. 
 
 Shell ot moderate size, composed of two or more(t) rapidly-increasing 
 volutions, enrolled on the same plane, and entirely disconnected ; the 
 inner ones apparently leaving a broad, open umbilical space. Shell 
 rather rapidly increasing in size with increased age. Volutions slightly 
 flattened, on the back vertically compressed and transversely oval in 
 section j the vertical diameter being only about two-thirds as great as 
 the dorso-ventral in the larger part of the shell, the greatest height 
 being nearest to the ventral margin. 
 
 Surface of the shell marked by strong, distant, transverse, encircling 
 ridges, which are directed slightly forward in passing from the dorsal to 
 the ventral margin, and in crossing the latter they become nearly obso- 
 lete. Occasional intercalated ridges occur at irregular distances on the 
 dorsal side. Intercostal spaces concave. The shell is further orna- 
 mented by two lines of obtusely rounded nodes, which are situated on 
 the ribs at the angles of the flattened dorsum. 
 
 Septa somewhat complicated and closely arranged, sothat the inner 
 lobes interfere with the extremities of the sinuses of the one in advance but 
 on the dorsal portion they are more distant. Siphonal lobe longer than 
 wide, deeply divided at the extremity and terminating in two large, strong- 
 ly serrated digitatlons, having one or two lateral spurs on their outer side. 
 First lateral lobe large, deeply bipartite, each branch terminating in 
 two or three unequal digitatious, and with several smaller spurs on the 
 sides above. Second lateral lobe much smaller than the first, deeply 
 bipartite, with numerous strong spurs irregularly arranged along the 
 margins. Antisiphonal lobe long, narrow and simple, but with long 
 lateral serrated spurs and a slightly tripartite extremity. First and 
 second sinuosities rather large, deeply divided by large auxiliary lobes 
 into two principal branches, which are again deeply divided. Third 
 sinus smaller than the others and divided into two principal branches. 
 The margins of all lobes and sinuses deeply serrated. 
 
 The species is described from an imperfect individual, and a second 
 smaller fragment of a larger specimen. They consist only of the con- 
 volute parts, and show no evidence of the deflection of the tube. It is 
 possible they are not rightly referred to the genus Ancyloceras, but are 
 more nearly related to the genus Anisoceras of Pictet, which differs 
 from the former genus in being irregularly helicoid. The example fig- 
 ured would seem to have been somewhat irregularly coiled, but this 
 may possibly be the effects of distortion, as the smaller coils of the shell 
 are considerably displaced. It differs from Ancyloceras also, as defined 
 by Mr. F. B. Meek (Pal. L T . S. Geol. Surv. Territ., p. 409), iu having 
 
43 
 
 the terminations of the lobes bipratite instead of tripartite ; but this 
 character does not appear to hold good among many of those referred 
 to the genus, and as we have not seen the septa of the type species we 
 are uncertain if it is an original feature of the genus or only an errone- 
 ously added one. 
 
 Formation and locality. In limestone referred to the Fort Pierre 
 group of the Upper Missouri Cretaceous, on the East Fork of Beaver 
 Creek, three miles west of Camp Jenney, Black Hills. 
 
 AXCYLOCERAS TRICOSTATUS, n. 8p. 
 
 Plate 15, fic?s. 7 and 8. 
 
 A single fragment of a sinistra, helicoid shell, the volutions of 
 which have been entirely separate and coiled upon the same plane, with 
 a rapidly increasing curvature, appears to possess features entirely dis- 
 tinct from those of any described species. The form of the volution has 
 been quadrangularly ovate in section, vertically compressed, with the 
 greatest vertical thickness at about the inner third of the width, and 
 slightly flattened on the dorsum. The shell is marked by a line of 
 strong, angular nodes on each dorsal angle, and by closely arranged, 
 subangular, encircling ridges or costa, which are directed slightly for- 
 ward in crossing from the ventral to the dorsal margin on the upper 
 side of the volution, and much more strongly so in crossing from the 
 upper to the lower side of the dorsal flattening, and are recurved below 
 and on the umbilical surface. The costa are arranged in sets of three, 
 the two adjacent ones of which unite in the nodes on the upper and 
 lower dorsal angles, while the third ridge of each set encircles the shell 
 between the nodes of two adjacent sets. Intercostal spaces concave. 
 
 Septa very complicated and distant; the space between two adjacent 
 ones equal to about one-third of the space occupied by the convolutions 
 of a single septum, at the point indicated. The dorsal lobe is almost 
 twice as long as wide, deeply divided at the lower extremity by a broad 
 tridentate sinus, each division being again divided into two widely 
 divergent, dentate branches. There are also two lateral dentate spurs 
 above on each side of the lobe. First lateral lobe large, but slender > 
 divided into two principal widely divergent branches, each of which is 
 again divided and furnished with several strong dentate spurs on the 
 margins; two other spurs of similar character exist on each side of the 
 lobe, one just below the bifurcation, and the other some distance above. 
 Second lateral lobe smaller than the first, deeply divided, with the 
 branches less divergent, but again divided, and the inner branches tri- 
 furcate, the outer branches short and strongly dentate. Autisiphonal 
 lobe small and simple, marked by one small spur on each side above, 
 and two larger curved and dentate ones below ; the central termination 
 being minutely tridentate at its extremity. First lateral sinus large, 
 very deeply divided into two principal branches, each of which is 
 
44 
 
 deeply divided above and strongly lobed on the sides. Second sinus 
 smaller, less deeply and unequally divided, the outer half smallest and 
 deeply lobed, the other less deeply so. Antisiphonal sinus very large 
 (considering the parts separated by the antisiphonal lobe as one sinus), 
 the antisiphonal lobe dividing it nearly to the base, and the divisions 
 again very deeply divided and deeply lobed on the sides. Siphuncle 
 small, situated between the lines of nodes and marginal. 
 
 This species differs from Ancyloceras Jenneyi in being sinistrally 
 coiled, and in the character of the ridges of the surface and angular 
 nodes. We know of no other species described with which it is enough 
 related to require a comparison. 
 
 Formation and locality. In limestone at the top of the Fort Pierre 
 group, on the Cheyenne, near French Creek, Black Hills, Dakota. 
 
 PTYCHOCERAS MEEKANUM, n. sp. 
 
 Plate 16, figs. 1 and 2. 
 
 Shell of small size, subcylindrical or vertically compressed, giving a 
 somewhat oblate-transverse section, very gradually increasing in diam- 
 eter with the increased length ; smaller limb slender, gently curved or 
 bent in the middle of its length, so as to give the earlier and middle 
 portions of the shell an angle of about 135 to each other. Larger 
 limb or outer chamber closely appressed and slightly embracing the 
 smaller, and extending to near the middle of the curvature. 
 
 Surface of the entire shell marked by strong, simple, sharply angular, 
 oblique, encircling ridges, with wider, deeply concave interspaces, very 
 regularly increasing in distance from the apex outward, and on the 
 dorsal region by two longitudinal rows of spines or spiniform tubercles, 
 situated at about or nearly one-sixth of the circumference of the tube 
 from each other, and on the crests of the ridges. The encircling ridges 
 are directed obliquely forward in passing from the ventral to the dorsal 
 surface in the smaller limb, but have the opposite direction on the 
 larger ; space between the lines of nodes very gently concave. 
 
 Septa approximate, but more distant than the surface-ridges of the 
 shell, deeply lobed, and the lobes and sinuses somewhat complicated. 
 The dorsal or siphonal lobes are nearly as wide as long, broadly forked 
 at the extremity, and the outer side of the forks marked by several 
 short rounded digitations. First lateral lobe divided into two diverging 
 branches, with lobed margins. Second lateral lobe narrower and more 
 slender than the first, and more deeply forked ; the division being 
 marked by short rounded digitations. Ventral or autisiphonal lobe 
 small, but deeply forked, and the margins sinuous. Sinuses nearly 
 equal in size, each of them deeply divided in the middle by an auxiliary 
 lobe ; slightly bifid in the first and second but simple in the third ; 
 division of the sinuses marked by short rounded digitations. Siphon 
 of moderate size, marginal, and placed between the lines of nodes. 
 
45 
 
 Before entering upon a critical study of the specimens before us, we 
 bad supposed them to be identical with Ptychoceras Mortoni M. & H., 
 and hesitated to consider them as distinct ; but there are so many 
 points of difference, and the variations are so great, that it appears im- 
 possible to avoid this conclusion, and equally difficult to unite the two 
 forms here mentioned. More especially is this the case if any reliance 
 is to be placed on the structure and location of the septa. We are quite 
 well aware that this latter feature is one liable to great variation, de- 
 pendant upon the growth of the individual ; but the lobations in the 
 septa at the smaller extremity of the specimen figured is much more 
 complicated than that shown by Mr. Meek, to exist in the type specimen 
 of P. Mortoni. Beside the difference in the septa, the form of the tube 
 varies in being wider than high, the reverse of that species, and the 
 antisiphonal surface of the tube is always flattened, and the costa 
 always simple. 
 
 Formation and locality. In limestone of the Fort Pierre" group, oil 
 Beaver Creek. Black Hills. 
 
 PTYCHOCERAS CRASSUM, n. sp. 
 
 Plate 16, figs. 3-5. 
 
 Entire form of shell unknown. The portion preserved is rather robust 
 in habit and the shell much thickened, except on the ventral surfaces. 
 Transverse section subcyliudrical or slightly compressed in a dorso- ven- 
 tral direction, the larger limb being concave on the ventral side and 
 slightly embracing the smaller part. Tube regularly increasing in 
 diameter with increased growth. Shell ornamented by strong, sharply 
 angular, encircling ridges, which are directed forward in passing from 
 the ventral to the dorsal sides of the smaller limb, but have the oppo- 
 site direction on the larger part; also by two longitudinal lines of 
 pointed nodes or spines on the dorsum, which are separated by a 
 moderately wide, slightly concave space. 
 
 Septa distant, one septum nearly equaling two of the transverse 
 ridges, except near the bending of the tube where there are two o the 
 septa placed nearer to each other, beyond which the shell is not sep- 
 tate. Lobes and sinuses of the septa somewhat complicated; the 
 siphonal lobe longer than wide, and broadly forked at the extremity. 
 First lateral lobe large, divided into two principal branches, the outer 
 one being again deeply divided, and the margins of the branches serrato- 
 digitate. Second lateral lobe smaller than the first, divided into three 
 short serrate digitations. Antisiphonal lobe small and simple, marked 
 only by two short digitations on each side. First and second sinuses 
 much larger and broader than the lobes, deeply divided in the middle 
 by a small serrated auxiliary lobe, and the divisions each again divided 
 and serrate. Antisiphonal sinus a little smaller than the others, but 
 more deeply divided by the antisiphonal lobe, and the branches again 
 
46 
 
 deeply divided. All the margins of the lobes and sinuses are charac- 
 terized by small, rounded serrations. Siphuucle of moderate size, mar- 
 ginal and situated between the lines of nodes. 
 
 The distinction between this and the preceding species consists in 
 its large size, more robust habit, and thicker shell, and in the more 
 distant and much more complicated septa. It is still further removed 
 by these characters from P. Mortoni M. & H., as well as by the simple 
 ridges. 
 
 Formation and locality. In limestone of the Fort Pierre group, on Old 
 Woman's Fork, Black Hills. 
 
 LIST OF FOSSILS DESCRIBED IN THE KEPOKT OF THE 
 PALEONTOLOGY OF THE BLACK HILLS. 
 
 POTSDAM GROUP. 
 
 Name. 
 
 Locality. 
 
 Palseochorda prima, D. sp 
 
 Pal reopb yens occidentals, D. sp, 
 sp, uudet 
 
 INCERTECEDES. 
 
 Scolitnus, sp. 
 
 BRACHIOPODA. 
 
 Lingulepis piunaformis, Owen 
 
 cuueolus, n. sp 
 
 perattenuatus, n. sp 
 
 Dakotensis, Meek & Hayden 
 
 Obolus ? pectenoides, Whitf 
 
 Obolella polita, Hall 
 
 Obolella naua, M. & H 
 
 CRUSTACEA. 
 
 Crepicephalus (Loganellns) centralis, n. sp. 
 planus, n. sp .. 
 
 Head of Red Water Valley. 
 Do. 
 Do. 
 
 Warren's Peak. 
 
 Red Canon Creek. 
 
 Do. 
 
 Do. 
 Castle Creek. 
 
 Do. 
 Red Water Canon. 
 
 Do. 
 
 Castle Creek. 
 Do. 
 
 JURASSIC. 
 
 RAD I AT A. 
 
 Asterias? dnbium, n. sp 
 
 Pentacrinus asteriscus, M. & H. 
 
 BRACHIOPODA. 
 
 Lingula brevirostris, M. & H... 
 Rbynchonella inyrina, H. &. W 
 
 Spear's Fork of Red Water Creek. 
 Big Horn Mountains. 
 
 Spear's Fork of Red Water Creek. 
 Red Canon Creek, 
 
47 
 
 List of Fossils j &c. Continued. 
 JURASSIC. 
 
 Name. 
 
 LAMELLIBRANCHIATA. 
 
 Locality. 
 
 Ostrea strigilecula, White Belle Fonrcbe, Sun-Dance Hills, 
 
 and near Beaver Creek. 
 
 Gryphsea calceola var. Nebracensis, M. & H j Big Horn Mountains. 
 
 Pecten Newberryi, n. sp 
 
 Camptonectes bellistriata, Meek ! Belle Fourche. 
 
 extenuatus, M. & H i East of Belle Fourcbe. 
 
 Pseudomonotis (Eumicrotis) curta, Hall ! Two miles south of Belle Fouicbe, 
 
 orbiculata, n. sp Red Water Valley. 
 
 Avicula (Oxytoma) mucronata, M. & H Two miles south of Belle Fourche. 
 
 Ger villia recta, Meek in MS Sun-Dance Hills. 
 
 Grammatodon inornatus, M. & H 
 
 Mytilus White!, n. sp j Sun-Dance Hills. 
 
 Volsella (Modiola) formosa, M. & H i Big Horn Mountains. 
 
 pertennis, M. & H | (September 20.) 
 
 Astarte fragilis, M. & H | Red Water Valley. 
 
 Trapezium bellefourchensis, n. sp j East of Belle Fourche. 
 
 subequalis, n. sp j Red Canon Creek. 
 
 Pleuromya Newtoni, n. sp j Two miles south of Belle Fourche. 
 
 Tancredia ( ?) inornata, M. & H East of Belle Fourche. 
 
 corbuliformis, n. sp Do. 
 
 bulbosa, n. sp Do. 
 
 postica, n.sp Do. 
 
 Warreuana, M. & H I Red Water Valley. 
 
 Dosinia Jurassica, n. sp j East of Belle Fourche, &c. 
 
 Psammobia (?) prematura, n.sp j Do. 
 
 Thracia snblevis, M. & H Red Water Valley. 
 
 Neaera longirostra, n.sp Do. 
 
 Saxicava Jurassica, n. sp Do. 
 
 CEPHALOPODA. 
 
 Ammonites cordiformis, M. & H ! Red Water Valley. 
 
 var. distans | Two miles south of Belle Fourche. 
 
 Belemnites densus, M. &H East of Belle Fourche. 
 
 CRETACEOUS. 
 
 Systematic name. 
 
 Division. 
 
 Locality. 
 
 LAMELLIBRAXCHIATA. 
 
 Cyncyclonema rigida. M. & H 
 
 Pteria linguiformis, Evans & Shurn. .. 
 
 (Oxytoma) Xebrascana, E. & S. 
 (Pseudopteria) tibrosa, M. &H. 
 
 sublse vis, n.sp.. 
 Inoceramus problematicns, Schlott... 
 
 fragilis, H. & M 
 
 altus, Meek 
 
 perplexus, n. sp 
 
 sublsevis, H. & M 
 
 Sagensis, Owen 
 
 No. 4. 
 No. 4. 
 
 No. 4. 
 No. 4. 
 
 No. 4 
 
 Nos.2and3. 
 Nos. 2 and 3. 
 No. 2 
 
 No. 2 
 
 No. 4. . 
 
 No. 4.. 
 
 Forks of the Cheyenne River. 
 Chevenne River, near French 
 
 Creek, &c. 
 Sage Creek. 
 Cheyenne River, near Rapid 
 
 Creek. 
 
 Old Woman's Fork. 
 East Fork of Beaver Creek. 
 Beaver Creek. 
 Belle Fourche, 10 miles west of 
 
 Crow Creek. 
 Belle Fourche, 10 miles west of 
 
 Crow Creek. 
 Forks of the Cheyenne River. 
 
48 
 
 List of Fossils, &c. Continued. 
 CRETACEOUS. 
 
 Systematic name. 
 
 LAMELLIBRANCHIATA Continued. 
 
 Inoceramus Simpsoni, Meek 
 
 Vanuxemi, M. & H 
 
 var. ., 
 
 Barabini, Morton 
 
 tenuilineatus, M. & H . . . 
 Endocostea typica, u. sp 
 
 sulcata, Roemer 
 
 Idonearca Shuinardi, M. & H 
 
 Nucula planimarginata, M. & H | 
 
 Nuculana bisulcata, M. & H 
 
 Division. 
 
 Locality 
 
 subequilatera, n. sp 
 
 YoldiaEvansi, M. &.H 
 
 Lucina occidentals, Morton 
 
 ventricosa, H. & M 
 
 (Diplodonta)subundata,H.&M. 
 
 Crassatella subquadrata, n. sp 
 
 Astarte Evansi, H. &M 
 
 Veniella humilis, M. & H 
 
 Sphaeriola transversa, n. sp 
 
 Dosinia Missouriana, Morton 
 
 Thetis circularis, M. & H 
 
 Leiopistha (Cymella) Meeki, n. sp 
 
 Thracia subgracilis, n. sp 
 
 Nesera Moreauensis, M. & H ? 
 
 GASTEROPODA. 
 
 Fasciolaria (Cryptorbytis) fusiformis, 
 
 H. & M. 
 
 Fasciolaria (Cryptorhytis) contorta, M. 
 (Piestocbeilus) Culbert- 
 soui, M. & H. 
 
 Fasus Shumardi, H. & M 
 
 Cheyennensis, n. sp 
 
 Aporrbais Newberryi, Meek 
 
 Meeki, n.sp 
 
 (Goniocbeilus) Castorensis, 
 n. sp. 
 
 Ancliura ? sublaevis, M. & H 
 
 CDrepanocheilus) Nebracen- 
 
 sis,E.&S 
 
 Lunatia concinna, H. &. W 
 
 Vanikora ambigua, M. & H 
 
 No. 4 
 
 No. 4 
 
 No. 4 
 
 No. 4.. 
 
 No. 4 
 
 Nos. 4 and 5. 
 N os. 4 and 5. 
 No. 5....... 
 
 No. 4 
 
 Nos. 4 and 5. 
 
 No. 4 
 
 No. 4 or 5.. 
 
 Nos. 4 and 5 
 No. 4 
 
 No. 4.. 
 
 No. 4? 
 
 No. 4 
 
 No. 5 , 
 
 No. 5 
 
 No. 4.... 
 No. 4 
 
 No. 5 
 
 No. 4 
 
 No. 4.. 
 
 No. 4 
 
 No. 4 or 5... 
 No. 4 or 5... 
 
 No. 2 
 
 No. 4. 
 
 No. 5 
 
 No. 4 
 
 No. 4 or 5... 
 
 No. 4 
 
 No. 4 or 5... 
 
 No. 4 
 
 No. 4.. 
 
 ! Old Woman's Fork. 
 
 Do. 
 Belle Fourche, 10 miles west of 
 
 Crow Creek. 
 
 Cbeyenne River, near Box Elder 
 Creek. 
 
 Old Woman's Fork. 
 
 Loose on Beaver Creek. 
 
 Cbeyenne River, near Old Wo- 
 man's Fork. 
 
 Cbeyeune River, (May 31.) 
 
 Cbeyenne River, near' Box Elder 
 Creek. 
 
 Cbeyenue River, near French 
 Creek. 
 
 Old Woman's Fork, &c. 
 
 Cbeyenne River, near Rapid 
 Creek. 
 
 Cbeyenne River, near Rapid 
 Creek. 
 
 Cbeyenne River, near Rapid 
 Creek. 
 
 Cheyenne River. 
 
 Cbeyenne River, near Rapid 
 Creek. 
 
 Cbeyenne River, near Old Wo- 
 man's Fork. 
 
 Cheyenne River, near Old Wo- 
 man's Fork. 
 
 Cheyenne River. 
 
 Cheyenne River, near Rapid 
 Creek. 
 
 Dead Man's Rapids, Upper Mis- 
 souri. 
 
 Cheyenne River, near Rapid 
 Creek. 
 
 Forks of the Chevenne River. 
 
 Cbeyenne River, near Rapid 
 
 Creek. 
 
 Old Woman's Fork. 
 Near French Creek. 
 
 East Fork of Beaver Creek. 
 Cheyenne River, near Rapid 
 
 Creek. 
 
 Rio de la Plata. 
 Cheyenne River, near Rapid 
 
 Creek. 
 East Fork of Beaver Creek. 
 
 Near Box Elder Creek. 
 East Fork of Beaver Creek. 
 
 Cheyenne River, near Rapid 
 
 Creek. 
 Cheyenne River. 
 
49 
 
 List of Fossils, &c. Continued. 
 CRETACEOUS. 
 
 Systematic name. 
 
 Division. 
 
 Locality. 
 
 GASTEROPODA Continued. 
 Amauropsis paludinaeformis, H. &M.. 
 Margarita Nebracensis, M. & H 
 
 Anisomyon alveolus, M. & H 
 subovatus, M. &H 
 
 patelliformis M & H 
 
 No. 4 
 No. 4 
 
 No. 4 
 No. 4 
 
 No. 4. ... 
 
 Cheyenne River, near Box Elder 
 Creek. 
 150 miles above mouth of Yellow- 
 stone. 
 Old Woman's Fork. 
 Do. 
 Do. 
 
 borealis Morton 
 
 No 4 
 
 Cheyenne River. 
 
 Akera glans-oryza n sp 
 
 No. 4 
 
 Chevenne River, near French 
 
 Haminea subcylindrica, M. & H 
 
 No. 4 
 No. 4 
 
 Creek. 
 Old Woman's Fork. 
 Cheyenne River, near Rapid 
 
 CEPHALOPODA. 
 
 Nautilus Dekavi var Montanensis M 
 
 No. 4 
 
 Creek. 
 Cheyenne River near Rapid 
 
 Prionocyclus Wyomingensis, Meek 
 Scaphites nodosus Owen . 
 
 No. 2 
 No. 4 
 
 Creek. 
 Chevenne River, near Rapid 
 
 var. brevis, Meek . . 
 
 quadran gu- 
 laris Meek 
 
 No. 4 
 
 No 4 
 
 Creek. 
 Cheyenne River, near Rapid 
 Creek. 
 
 Cheyenne River, near Rapid 
 
 plenus M & IT 
 
 No. 4 . . . 
 
 Creek. 
 
 Warreni, M. & H 
 Wyomingensis, M. & H 
 Helicoceras Stevensoni, n. sp 
 Heteroceras Newtoni, n. sp 
 ? Nebracensis, M. & H . . . 
 Ancycloceras Jenneyi, n. sp 
 tricostatum, n. sp 
 
 Ptychoceras Meekanum, n. sp 
 erassuin, n. sp 
 
 No. 2 
 No. 2 
 No. 4 
 No. 4 
 No. 4 or 5... 
 No. 4 
 No. 4 
 
 No. 4.. 
 No. 4 
 
 East Fork of Beaver Creek. 
 Do. 
 West of Beaver Creek. 
 Do. 
 East Fork of Beaver Creek. 
 Do. 
 Cheyenne River, near French 
 Creek. 
 Beaver Creek. 
 Old Woman's Fork. 
 
 4 B H 
 
 . O 
 
YC 36318