INTBODUCTION TO MAMMALIAN" PALEONTOLOGY 



31 



Figure 23. — Heads of lower Eocene and modern jjerissodactyls, showing changes of proportion and of the lip 



structure 



Based on materials in the American Museum of Natural History. Scales various. A, Head of the lower Eocene tapiroid Sijstemodon, very sim- 

 ilar to that of Eohippus and of Lambdotherium; B, head of middle Eocene tapir Hdaleies, in which a prehensile upper lip first appears; 

 C, head of the modern tapir Tapirus, whose prehensile upper lip forms a short proboscis; D, head of middle Eocene cursorial rhinoceros 

 Hyrachyus, still of primitive proportions; E, head of existing white rhinoceros {EhiTicccrcs ( Caalothcriuw) simum) with extremely 

 broad, grazing type of lip structure. 



