the forms exhibited on its under side, were truly what they appeared to be, locomotive organs." On account of his doubts, the specimen was submitted by him during the past year to the Geological Society of London; and for the same reason, notwithstanding the corroboration there received, he offered to place the specimen in my hands for examination and report. Besides giving the specimen an examination myself, I have submitted it also to Mr. A. E. Verrill, Prof. of Zoology in Yale College, who is well versed in the invertebrates, and to Mr. S. L. Smith, assistant in the same department, and excellent in crustaceology and entomology. We have separately and together considered the character of the specimen, and while we have reached the same conclusion, we are to be regarded as independent judges. Our opinion has been submitted to Mr. Billings, and by his request it is here published. The conclusion to which we have come is that the organs are not legs, but the semi-calcified arches in the membrane of the ventral surface to which the foliaceous appendages, or legs, were attached. Just such arches exist in the ventral surface of the abdomen of the Macrura, and to them the abdominal appendages are articulated. This conclusion is sustained by the observation that in one part of the venter three consecutive parallel arches are distinctly connected by the intervening outer membrane of the venter, showing that the arches were plainly in the membrane, as only a calcified portion of it, and were not members moving free above it. This being the fact, it seems to set at rest the question as to the legs. We would add, however, that there is good reason for believing the supposed legs to have been such arches in their continuing of nearly uniform width almost or quite to the lateral margin of the animal; and in the additional fact, that, although curving forward in their course toward the margin, the successive arches are about equidistant or parallel, a regularity of position not to be looked for in free-moving legs. The curve in these arches, although it implies a forward ventral extension on either side of the leg-bearing segments of the body, does not appear to afford any good reason for doubting the above conclusion. It is probable that the two prominences on each arch nearest the median line of the body, which are rather marked, were points of muscular attachment for the foliaceous appendage it supported. With the exception of these arches, the under surface of the venter must have been delicately membranous, like that of the abdomen of a lobster or other macruran. Unless the under surface were in the main fleshy, trilobites could not have rolled into a ball; and the fact that this particular species of Asaphus is not found so rolled may be owing to the unusual size or firmness, and also the position, of these slender arches. ART. XLVIII.—Description of some new Fossil Serpents, from the Tertiary Deposits of Wyoming; by Professor O. C. MARSH, of Yale College. AMONG the Reptilian fossils discovered by the Yale College party, during their explorations last summer in the Green River Tertiary basin, west of the Rocky Mountains, were the remains of several species of Serpents, which are of peculiar interest, as they are the first extinct Ophidians found in the interior of the continent, and, with the exception of three species from the Eocene marl of New Jersey,* the only fossil representatives of this order yet detected in this country. These remains, which are now in the Peabody Museum of Yale College, consist mainly of vertebræ, of various sizes, many of them more or less injured, but in general with the most characteristic parts well preserved. Nearly all the specimens obtained evidently belonged to constricting serpents, closely related to the modern Boas of South America, although considerably smaller, and generically distinct. A few of the specimens indicate snakes of moderate size, with apparently quite different affinities. In comparing the larger series of these fossil vertebræ, especially those from near the middle of the trunk, with the corresponding vertebræ of the living species of Boa, a strong resemblance will be noticed in the more important characters, especially in the transversely elliptical outline of the articular cup and ball; in the obtuse lateral elevation extending from the diapophyses to the articular ball; and in the elongated median ridge on the inferior surface of the centrum. The differences between them, however, are important, and indicate clearly that the fossil specimens represent a separate genus, for which the name Boavust is proposed, in allusion to the not improbable relationship of the two types. In the extinct genus, the articular ball and cup are more nearly vertical, and their outline forms a more full transverse ellipse. The neural arch is proportionally more elevated, and has on either side a low ridge, extending backward from the articular face of the zygosphene, and expanding over the zygantral cavities. The latter are more deeply excavated than in Boa. The neural spine is shorter, its antero-posterior extent, in the specimens in which it is preserved, being greater than its height. The diapophyses are convex throughout, while those of Boa are more or less concave on the lower part of their articular face. The lateral elevation, extending from the diapophyses to the articular ball, is, in Boavus, situated lower on *This Journal, vol. xlviii, p. 397, Nov. 1869. Boa, and avus, grandfather. the centrum, and is less rounded. The hypapophysial ridge, also, is sharper, and extends nearer to the inferior edge of the articular ball. From the vertebræ of Dinophis Marsh, which genus includes the only fossil Ophidians hitherto found in this country, as well as from those of the nearly allied Palæophis of Owen, the specimens of Boavus here described are widely separated, especially by their greatly inferior size; by the shorter neural spine; by the broader zygosphene, which exceeds in transverse diameter the articular cup, as in most modern serpents; by the elevation extending backward from the zygosphene; by the more expanded diapophyses; and by the well developed lateral and inferior median ridges on the centrum. The vertebræ of Boavus, however, resemble those of Palæophis and Dinophis, and differ from those of Boa, Crotalus, and many other modern serpents, in having the sides of the neural canal extended forward nearly to the edge of the articular cup. Boavus occidentalis, sp. nov. This species is established on eight vertebræ, nearly all from the middle dorsal region. They evidently represent several individuals, as they differ considerably in size, and were found at three separate localities. They indicate constricting serpents between six and eight feet in length. The neural arch in this species is elevated and massive. The neural spine is short, and triangular at its base, which rests on the posterior three-fourths of the arch. The zygosphene is convex above, slightly excavated in front, and without a median tubercle. The neural canal has a distinct median epapophysis on its floor, and sharp lateral ridges, which give it a sub-trifoliate outline. The diapophyses are auriform, and project below the inferior margin of the cup. The hypapophysis is a sharp ridge, beginning at the margin of the cup, and ending, just before reaching the ball, in an obtuse projection. The principal dimensions of one of the largest vertebræ of this species are as follows: Length of centrum from edge of cup to convexity of ball, 4.50 lines. Transverse diameter of cup, Vertical diameter of cup,- - Transverse diameter of zygosphene at base, Distance from top of zygosphene to lower margin of cup, 5. Vertical diameter of ball,... Width of neural canal in front, Height of neural canal in front,. The various specimens representing this species were found. in September last by H. B. Sargent, A. H. Ewing, and the writer, at Grizzly Buttes, near Fort Bridger, Wyoming Territory. The geological horizon is probably Eocene.* Boavus agilis, sp. nov. This species, which was nearly the same in length as the preceding, although apparently much more slender, is indicated by five vertebræ, all from the dorsal region, and representing two or more individuals. They may readily be distinguished from the corresponding vertebræ of B. occidentalis, by the proportionally more elongated centrum; by the rounder and more inclined cup; by the more expanded anterior zygapophyses; by the diapophyses, which do not extend below the inferior surface of the centrum; and by the hypapophysial ridge, which is more obtuse, and in its anterior portion expands rapidly until it disappears in the margin of the cup. The largest vertebra of this series has the following dimensions: Length of centrum from edge of cup to convexity of ball, 4.25 lines. Transverse diameter of cup, Vertical diameter of cup, Vertical diameter of ball, Width of neural canal in front,. 2.50 66 The specimens on which this species is based were discovered by the writer, near Fort Bridger, in the same formation as the remains above described. Boavus brevis, sp. nov. The serpents representing this species were considerably smaller than those described above, and evidently much shorter in proportion to their bulk, being probably not more than four or five feet in length. The only remains obtained consist of three dorsal vertebræ, all in good preservation, and evidently belonging to two different individuals. These vertebræ have the centrum unusually short, its extent measured on the inferior surface scarcely exceeding the transverse diameter of the zygosphene. The neural arch is low, and bears on its posterior two-thirds the neural spine, which is quite short, and truncated. The zygosphene is less massive than in the preceding species, and has a slight median swelling on the anterior margin of its base. The dimensions of the most perfect of these vertebræ are as follows: Length of centrum from edge of cup to convexity of ball, 2.20 lines. Transverse diameter of cup, Vertical diameter of cup,- Transverse diameter of zygosphene at base,. 1.60 1.25 66 66 1.85 66 1.00 ⚫90 66 *This Journal, III, vol. i, p. 192, March, 1871. Distance from top of zygosphene to lower margin of cup, 2.80 Height of neural canal in front,. The specimens here described were found by H. B. Sargent, in the same fresh-water Tertiary deposits, and near the same locality, as the two preceding species. Lithophis Sargenti, gen. et sp. nov. This species and genus are at present represented by three trunk vertebræ, only one of which, however, is sufficiently well preserved to show all its more important characters. The specimens indicate a small serpent about four feet in length, and probably, like the preceding species, allied to the constrictors. From the vertebræ of Boavus, as well as from those of the other fossil Ophidians discovered in this country, the present specimens may be readily distinguished by the more compressed centrum, and especially by the articular cup and ball, which are circular in transverse outline, as in the Arican Eryx, and stand nearly at right angles to the axis of the centrum. The anterior zygapophyses, also, are more extended outward, and their articular faces have a greater antero-posterior expansion than in any of the described species. The diapophyses have their articular surfaces divided by a horizontal groove, having a rounded tubercle above, and a pointed projection below, as in the modern Bascanion. There is no lateral ridge extending from the diapophyses to the articular ball, as in Boa and Boavus, the converging sides of the centrum being nearly flat. The hypapophysis is reduced to a wedge-shaped ridge, extending the whole length of the centrum, and having its sharp apex below the inferior margin of the cup. The floor of the neural canal has a prominent, obtuse median ridge throughout its whole length, but no lateral ridges are apparent. The principal measurements of the best preserved vertebra are as follows: Length of centrum from edge of cup to convexity of ball, 2.80 lines. Transverse diameter of cup, Vertical diameter of cup,- Vertical diameter of ball, Width of neural canal in front,. Distance from end of anterior zygapophysis to hypapophysis, 1.35 66 1.35 66 Distance between ends of the anterior zygapophyses, - 4:50 For the extinct genus manifestly indicated by the fossils here described, the name Lithophis is proposed, and the species they represent may appropriately be called Lithophis Sargenti, after the discoverer, Mr. H. B. Sargent, of the Yale Scientific party, who found the specimens in the Eocene "Mauvaises Terres" beds at Grizzly Buttes, near Fort Bridger. * Aibos, stone, and 'Opis, serpent. |