114 Bulletin American Museum of Natural History. [Vol. X, 



will probably establish a complete transition between P. labiatum 

 and the John Day species. 



Gomphotherium Cope. 



It is especially to Cope that we are indebted for the discovery 

 of Camels in the John Day P^eds. The first remains secured by 

 him from this horizon were referred to Poebrotherium, but later 

 he established the genus Gomphotheriuni' for their reception, 



Fig. II. Side view of skull of Go»iphotherin7n ste>-nl>ergi. 



which he distinguished from Pofbrot/nriairi by the more simpli- 

 fied character of the crown, and the one-rooted condition of the 

 first superior ]:)remolar. As this distinction was founded largely 

 upon error, I am now able to give the more important and true 

 characters which serve to separate the two genera in a satisfactory 

 manner. 



In PoebrotJieyiiiiii the inferior canine is either in contact with 

 the outer incisor, or is se])arated from it by a very short dias- 

 tema, and the form of the canine is either like that of an incisor 

 or very imperfectly caniniform. In Gomphotherium, on the other 

 hand, the inferior canine is either separated from the outer 

 incisor by a very distinct diastema or the diastema is absent, 

 and the shape of the canine is strongly pointed and recurved, as 



' ' The Phylogeny of the Camelidsc,' Amer. Nat., t886, p. 6i8. 



