Douglass : Rhinoceroses from North Dakota and Montana 261 



the borders are folded or turned inward apparently for the purpose of 

 strengthening the nasals for the support of the anterior weapon of de- 

 fence The anterior portion of the frontal plane is slightly convex 

 transversely, but nearly flat. 



FIG. 3. Outline of back of skull of Aphelops ceratorhinus ? \. (No. 854.) 

 The paroccipital process is different from that of any other species 

 which I have observed. It is situated at some distance anterior to the 

 occipital condyles and there is a quite large concave space between the 



Fig. 4. Basi-occipital view of skull of Aphelops ceratorhinus ? \. (No. 854. ) 



two The process is concave on the anterior and posterior surfaces. 

 The anterior surface is trough-shaped, but the posterior has a large 

 depression at the base of the process, and farther down a concavity 



