Douglass : Rhinoceroses from* North Dakota and Montana 257 



moderately broad and converge backward until they are 2 cm. apart ; 

 then they begin to diverge 8 cm. anterior to the occipital crest. The 

 upper posterior portion of the skull resembles that of specimen No. 

 840, which is described in this paper, but in the latter specimen the 

 supratemporal ridges diverge more rapidly toward the occiput. 



There are two infraorbital foramina in the maxillary above the 

 third and fourth premolars. The 

 lower of these foramina is large 

 and round. The other foramen 

 is just above and a little posterior 

 to the first and is oblong-oval in 

 form, with the apex of the oval 

 anteroinferior. The malar is 

 rather shallow beneath the orbit, 

 but is deeper farther back. The 

 posterior upper angle of the zygo- 

 matic portion of the squamosal is 

 low. The external auditory open- 

 ing is entirely surrounded by the 

 temporal bone, as the postglenoid 

 and posttympanic portions are in 

 contact by the enlargement and 

 forward trend of the posttympanic, 

 which is large, rounded on the 

 outer surface, and somewhat 

 roughened by shallow depressiosn. 

 The paroccipital processes, as seen 

 from the side, are quite broad. 

 They are near the occipital con- 

 dyles. 



The occiput appears to have 

 been nearly perpendicular, not 

 much inclined either forward or 

 backward. It is low in propor- 

 tion to the length of the skull and 

 is broad, not narrowing rapidly 

 upward as in specimen No. 854 



{Aphelops ceratorhinus 7) . The middle of the occiput immediately 

 above the foramen magnum is very convex transversely and projects 

 backward overhanging that opening. 



