310 LAND MAMMALS IN THE WESTERN HEMISPHERE 



only a few belated stragglers reached the eastern hemisphere, 

 though the family may, nevertheless, have originated there. 



In the lowest of the three substages of the White River 

 Oligocene the most conspicuous and abundant fossils are 

 the ftitanotheres, the latest members of which were huge 

 animals of almost elephantine proportions. They belonged to 

 four parallel, or rather slightly divergent, phyla, differing in 

 the development of the horns, in the shape of the head and in 

 the relative length and massiveness of the limbs. The teeth 

 were all low-crowned, or brachyodont, the canines much too 

 small to have been of any service as weapons and the incisors 

 had curious little, button-shaped crowns, which can have had 

 little or no functional importance, since they show hardly 

 any wear, even in old animals. With such front teeth, a 

 prehensile lip and long tongue would seem to have been neces- 

 sary for gathering and taking in food. 



The ftitanotheres were one of two perissodactyl families in 

 which the premolars never became so large and complex as 

 the molars. The upper molars had a longitudinal outer wall, 



-1 ^^^-z B 



Fig. 16L — Second upper molar, left side, of jTitanotherium. A., masticating surface; 



B., outer side of crown. 



composed of two deeply concave cusps, and two internal 

 conical cusps, but no transverse ridges ; the lower molars 

 were composed of two crescents, one behind the other, a 

 pattern which was very widely distributed among the early 

 and primitive artiodactyls and perissodactyls. 



The so-called ''horns" were not strictly such, but a pair 



