904 



HISTORICAL GEOLOGY. 



The Tillodonts of Marsh, Avhich range from the Puerco through the 

 Bridger Eocene, fail of prototypic characters in having less than the normal 



Fig. 1518, Restoration of Coryphodon hamatus (x 5'j) ; a, fore foot; b, hind foot (x |). Marsh. 



number of incisors, with one of the pairs much elongated like those of a 

 Beaver and other Rodents, as shown in the figures of Tillotlierium fodiens of 

 Marsh. The name, from tlWw, bite, alludes to the long incisors. Psitta- 



1519-1523. 



1520 



Figs. 1519, Tillotherium fodiens, top view, ivith form of brain cavity (x J) ; 1520, same, skull and lower jaw ; 1521 

 a, b, same, ungual phalanx or claw, front and side view; 1522, T. latidens, last upper molar (x |) ; 1523, 

 Anchippodus minor, lower molar (x |). All from Marsh. 



cotherium of Cope is a genus of the group from the Puerco beds ; Anchippodus 

 of Leidy, from the Bridger group and the New Jersey Eocene ; and Tillo- 



