Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/70

 64 THE EXTINCT BATRACHIA, REPTILIA alveolus, and whose development had occasioned the absorption of half the fang of the functional tooth. On the basis of this tooth I am enabled to determine the distinctness of this crocodile from the T. antique. The crown, instead of being like that species, a cone with a circular section, with a narrow cutting longitudinal ridge rising abruptly from the surface on each side, in this tooth has a lenticular section, with the cutting ridges on the acute opposite angles. The external face is strongly convex, though not so much so as in T. antiqua. The edges are crenate, but not so as to produce a serration of the margin. Enamel finely obsoletely striate. The vertebra preserved is a posterior lumbar. The entire con ssification of the nenrapophysis indicates that the animal is adult ; their upper portions are lost. The diapophyses have had an oblique basis, rising anteriorly, their middle being opposite the plane of the neural canal, the whole length standing on the anterior two-fifths of the length of the ceutmm. The cup is subeircular, wider transversely ; the centrum is depressed ; below broad, with a median longitudinal concavity ; sides vertical. As compared with the dorsal vertebra of T. antiqua, the latter are much more compressed iu the centrum ; and although the posterior lumbars are always more depressed than the dorsals, yet the present seems too much so to have pertained to the same species. It differs from those of T. antiqua also, in that the floor of the neural canal is entirely plane and smooth ; in the latter it is deeply grooved, in consequence of the non-coalescence of the expanded bases of the neurapophyses. • Ft. In. Lin. Length fragment of mandible, 8 4. Diameter of alveolus, 11. Axial width from margin alveolus to symphysis above, do. do. do. do. below, 1 2 4. 8. Greatest width to median line (behind), 3 S. Long diameter crown, at middle of length, 8. Width muzzle, 2 8. Estimated length cranium, do. total length, 33 69 4 5. Length lumbar vertebra (centrum), 3 10.5 2 3.5 Width cup, Height cup, 2 0.8 The above estimate of length is based on the proportions of the Gavialis gangeticus as given by Outer. TIIECACHAMPSA ANTIQTJA, Leidy sp. Crocodilus antignus, Leidy. L. c. 1851, 307. Journ. Ae. N. Sci., II., 135. Tab. ?Thecachampsa contusor, Cope. Proc. A. N. Sci., 1867, 143. This species continues as•yet to be represented only by the specimens on which it was basal, viz., two teeth, two vertebra, an ungucal phalange, and a rib. These indicate a large species ; the vertebrae are even larger than that of the last, and the teeth will not enter its alveolae. It is probably the largest of the known Crocodiles of this country. Fig. 16. I have noticed only two dentinal cones in the two teeth we possess. The accompanying outlines are those of sections of the teeth of the present species, /\ -1 •m and the T. sicaria C. Fig. A. represesents the former and fig. B the latter. ) (K(1• The pecnliar form of the tooth on which T scontusor wasbased, is due I find to attrition • and partial destruction of the enamel. Ti A "Eocene" of Eastern Virginia from the banks of the Potomac. TIIECA.CLIAMPSA SERICODON, Cope. Proceed. Acad. Nat. Sei., Philad., 1867, p. 143. This species was established on fragments of three teeth from the Miocene of Maryland. Four additional and much more perfect teeth, with fragments of jaws, from New Jersey, presented by my friend, Dr. H. C. Wood, Jr., elucidate the characters of both species and genus.