18 HYPOSAURUS. 



dentinal substance. The base of the crown is excavated. The length of the 

 specimen is fourteen lines and a half; its diameter at base, six lines. 



The second specimen, Fig. 23, diti'ers from the former in being somewhat curved, 

 elliptical in transverse section, and in the fluting extending to the bottom of the 

 crown. The apex is Avorn off, and the specimen in its present state is ten lines 

 and a half long, by six lines and a half in diameter antero-posteriorly near the base. 



The two teeth dift'er fronr those of Pliogonodon, probably also from the Green- 

 sand of North Carolina, in which the crown is proportionately longer, and has its 

 surfaces subdivided into narrow planes and provided with a few interrupted vertical 

 plicEB. They differ also from those of Poli/gonodon, in which the crown of the tooth 

 is long and narrow and its surfaces subdivided into planes without folds or striae. 



Dr. Emmons, in his Report of the North Carolina Geological Survey, page 219, 

 fig. 38, has described and figured a large Crocodilian tooth, obtained from a bed of 

 Miocene marl, at Elizabethtown, Bladen County, N. C. The tooth, together with 

 some bones. Dr. Emmons nevertheless thinks originally belonged to the Green-sand 

 formation beneath. It has a conical crown, and a robust cylindrical fang ; is hollow, 

 and moderately curved. The crown is described as circular in transverse section, 

 and without carinae, or acute ridges separating the inner and outer surfaces, the 

 enamel of which is traversed with "irregular rugose ridges." The specimen is 

 referred to the genus Polyptyclwdon, under the name of P. rugosus. 



Another tooth, found with the preceding, described and figured in the same 

 chapter, page 220, fig. 39, and referred by Dr. Emmons to the same animal, appears 

 rather to have belonged to Mosasaurus. 



Fig. 12, Plate VIII, represents a dermal plate, which, together with a small 

 fragment of a jaw, and the mutilated crown of a tooth, were submitted to my 

 examinatiom from the Burlington Coimty Lyceum of Natural History. The dermal 

 plate measures two inches by twenty lines, and is without a carina. The fragment 

 of jaAV, much mutilated, is two and a half inches long, straight, and contains the 

 much curved fangs of two teeth. It indicates a small species of Gavial, or perhaps 

 belonged to the young of Tlioracosaurus Neocesariensis. The isolated crown of a 

 tooth closely resembles that of Fig. 7, Plate I, but is rather more curved. 



HYPOSAURUS. 



Hyposniiriis Rog;crsii. 



Byposaurus Ro(jersii, Owen, Quart. Jour. Geol. Soc. Lond. V, 1849, 380, pi. xi, figs. 7-10. 



Holcndii.i arutiilens, GiiiBKS (in part), Mem. on Mosasanrus, &c., Smithsonian Contrib. II, 1850, 9, pi. iii, fig. 13 



Among the fossil vertebrse, from the Green-sand formation of New Jersey, de- 

 scribed by Prof. Owen, in the Journal of the Geological Society of London, were 

 two specimens with biconcave bodies, which are referred to a genus of the Croco- 

 dilian family under the name of Hijposcmrus Rogersii. Prof. Owen remarks that 

 " the peculiar and distinctive character of these vertebrte is shown in the large size 

 and especially the great antero-posterior extent of the hypapophysis. Its base 

 occupies the wl\olc extent of the median line of the inferior surface between the 

 proiniuent borders of tlie anterior and posterior articular ends of the centrum." 



