Peterson: The Osteology of Promerycochgerus. 



157 



ridge also contracts suddenly, so that the lateral sides of the occii)Ut 

 are deeply excavated (see I-'ig. i). Below this excavated area the 

 occipital plate again expands broadly, very largely on account of the 

 great development of the post-temporal ridge. At its greatest lateral 

 expansion the latter ridge is divided, the anterior division extending 

 downward and slightly forward above the external auditory meatus, 

 and uniting with the superior border of the zygomatic process, while 

 the posterior division extends downward back of the meatus and 



Fig. I. Posterior view of skull of Promerycochceriis carrikeri, \ nat. size. 



finally is united with the lateral border of the paroccipital process. 

 The inferior half of the occipital plate is vertical, while superiorly it 

 overhangs the lower portion; laterally and below the auditory meatus 

 it is separated from the base of the zygomatic process by a deep 

 fissure which is not unlike that in the hippopotamus, though not so 

 completely filled up with bony structure as in the latter. The 

 occipital condyles are of relatively small size; they are well separated 

 from the occipital plate by the long neck of the exoccipitals; inferiorly 

 they are separated by a regularly rounded emargination, and there are 



