HISTORY OP THE PERISSODACTYLA 323 



do we get material which permits the making of definite state- 

 ments regarding the course of developmental changes. The 

 White River genus, f Protapirus, which is also found in the 

 middle OUgocene of Europe, was a much smaller animal than 

 any of the known Pleistocene or Recent species, barely more 

 than half the size, in fact. The teeth show that the small 



Pig. 169. — Skull of White River tapir (fProiapi7~us validus) , left side. Princeton Uni- 

 versity Museum. N.B. This figure is much less reduced than Fig. 168. 



tusks were canines, both above and below, and that the curious 

 substitution of the external upper inx!isor for the canine had not 

 yet taken place. The grinding teeth were identical in pattern 

 with those of the existing genus, but not all the premolars had 

 yet acquired the form and size of the molars. In the skull 

 the nasal bones had begun to shorten, but the change had not 

 yet made much progress, and the proboscis must have been in 

 merely an incipient stage of development. What Uttle is 

 known of the skeleton other than the skull was Uke that of the 

 modern genus, but the bones were much smaller and propor- 

 tionately lighter. 



The Eocene tapirs are still very imperfectly known ; all 

 that can be said of them is that they become successively 

 smaller as they are traced backward in time, and that in them 

 the premolar teeth were all smaller and simpler than the 



