1006 The Perissodactyla. 
É l 
Fic. 22. Aphelops fossiger Cope, skull, one-fifth natural size, from side and below; 
from Loup Fork beds of Kansas. From Marsh. 
f Elasmotherium, 
Peraceras. Rhinocerus. Ccelodonta. 
Aphelops. Ceratorhinus. Atelodus. 
oo Aceratherium. NG VA 
A 
| a. 
Czenopus. 
Fic. 23. Aphelops megalodus Cope, skull from above, one-sixth n 
From the Loup Fork bed of Colorado; original. 
The history of the Tarirrp# has been mainly pene Hy 
Scott. Their origin from the Protapirine division ish 
iate form 
cotheriinz cannot be doubted, but the intermed Lower 
been mostly lost.. The oldest genus appears 1m a followed 
cene of North America (White River), and t 18 
