THE ANTELOPES AND OXEN. 185 



the advantages, and they account for the gradual 

 disappearance of the primary groups and for the 

 origin of new species. 



In America we find the same circumstances. 

 Antelopes and oxen have, it is true, decreased in 

 a remarkable manner among the present American 

 fauna, but the abundance of the fossil forms is so 

 great that we can scarcely find fault with the 

 patriotism of the American naturalists, when we 

 find thenij in this case also, claiming their country 

 to have been the cradle of this group of Hoofed 

 animals. Of purely American types we will name 

 only the very numerous family of the Oreodonta, 

 which combines traits of the pig-shaped pair- 

 hoofed, or thick-skinned animals, i.e. the large 

 canines as weapons, and molars of the ruminant 

 type. They were so numerous in the Middle Eocene 

 that one stratum has been called after them, and, 

 together with this force of numbers, they show 

 that tendency to differentiate into races and 

 species which seems to be characteristic of pri- 

 mary forms. 



Although America was rich in the still indefinite 

 precursors of our present Euminants, it has re- 

 mained absolutely unproductive as regards Oxen. 

 For even the Diluvial ancestor of the North Ameri- 



