O. C. Marsh Vertebrate Lifein Ameticas == UB 
The premolars are all unlike the molars, the four canines are 
of large size, but the inner incisor in each jaw is lost in the 
fully adult animal. The nasals were without horns. There 
as been referred to the genus Aceratherium. This form has 
lost the canine and one incisor above, and two incisors below. 
In the Pliocene are several species closely related, and of large 
size. Above the Pliocene in America, no vestiges of the 
Rhinoceros have been found, and our American forms doubt- 
less became extinct at the close of this perio 
remarkable that the Miocene of the West, so greatly developed as 
™ . . 
the Isthmus of Panama appear all to be generically distinct 
from those of South America. 
In addition to these three Perissodactyle types — as 
e 
the fittest, have alone survived, and whose lineage ay 
