1898.] Osborn, Evolution of the Amblypoda. Part I. 



189 



lower canines, the lopho-selenodont molar teeth, and the broad- 

 topped skulls. These and other advances upon the Pantolambda 

 type were effected in the interval between the deposition of the 

 Torrejon or Upper Puerco and the Wasatch Beds. 



Fig. 14. Skull of Ccryphodon testis. Male specimen, No. 2867, as mounted in skeleton. 

 Lower jaw, No. 2872. Am. Mus. Coll. The back part of the skull is elevated by distortinn. 



Revision and Criteria of Species. 



Twenty-one species were named by Cope, with as little regard 

 for the laws of individual variation as for the association of 

 skeletons with teeth or of jaws with skulls. It is a priori improb- 

 able that such numerous species should have coexisted, consider- 

 ing that all the collections come from a few levels and a single 

 geographical region. Our knowledge of large living quadrupeds, 

 such as the African Rhinoceros, shows that rarely more than two 

 species of one genus coexist, and these have different local feeding 

 habits. The writer has found the same to be true of the Eocene 

 Titanotheres of Wyoming. Earle's revision of the s])ecies (1892), 

 therefore, marked a valuable advance but left much to be done, 

 owing to his lack of comparative material at the time. 



