68 Bulletin American Museum of Natural History. [Vol. XIX, 



moving backward; but it is probable that growth of other 

 parts makes compensations, so that the two fangs are always 

 closely opposed to each other. Cope {pp. cit., p. 301) has 

 described the mode of succession of the teeth of the dentary. 



Enchodus ferox Leidy. 



Enchodus ferox Leidy (J.), Proc. Acad. Nat. Sci. Phila. 1855, P- 397- 

 — Emmons (E.), Man. Geol. 2nd ed. i860, p. 214, fig. 1824. — 

 Cope (E. D.), Vert. Cret. Form. West, 1875, p. 277. — Loomis 

 (F. B.), Palseontogr. XLVI, 1900, p. 277. — Woodward (A. S.) , 

 Cat. Foss. Fishes, IV, 1901, p. 204. — Hay (O. P.), Bibliog. and 

 Cat. Foss. Vert. N. A. 1902, p. 389. 



Enchodus pressidens Cope (E. D.), Proc. Amer. Philos.-Soc. XI, 1869, 

 p. 241; Vert. Cret. Form. West, 1875, p. 277. — Loomis (F. B.), 

 Palaeontogr. XLVI, 1900, p. 277. — Woodward (A. S.), Cat. 

 Foss. Fishes, IV, 1901, p. 205. — Hay (O. P.), Bibliog. and Cat. 

 Foss. Vert. N. A. 1902, p. 389. 



" Sphyrcsna" Morton (S. G.), Synop. Org. Rem. Cret. U. S. 1834, p. 

 32, pi. xii, fig. I. 



In the Cope Collection are two palatines belonging to the 

 genus Enchodus, both of which are labelled in Cope's hand- 

 writing. One of these. No. 2251, is labelled "Enchodus ferox'' ; 

 the other, No. 2250, ''Enchodus pressidens, not typical." 

 Fig. 50 represents the specimen of E. ferox. A study of these 

 has led to the conclusion that the two species, E. ferox and 

 E. pressidens, are identical. The characters which are relied 

 on to distinguish E. pressidens are the crescentic section of 

 the base of the palatine fang, the triangular 

 j^^^^^ section of the middle of the tooth, the grooves 

 ^^-^?^P bounding the cutting edges, and the projec- 

 T^^^^^ii tion of the base of the tooth beyond the 

 ■^ J I anterior margin of the palatine. 



|7 As to the crescentic base, this results from 



|/ the pressure of the hinder side of the new 



Fig. 50. Enchodus tooth against the base of the old tooth, and 



ferox \^e\Q.y . No. 2250. . 



X \. Palatine and there IS somc rcason for believing that the 



lang, with section. . 



concavity of the posterior side of the new 

 tooth diminishes somewhat after the old tooth has fallen 

 out. At any rate, such an explanation is suggested by a 



