PROMERYCOCHCERUS 



133 



The brain case is very narrow and small, and the size of the ridge along the parietosquamosal 

 suture is variable, but a ridge is always present. The external auditory meatus is small. The 

 narrow palate is flat between the premolars and concave between the molars, and the U-shaped 



Fig. 89. — Promerycochcerus macrostegus (Cope). Skull and jaw. HT. Cat. No. 7444 A.M.N.H. 1/3 nat. size. 



(Redrawn from Matthew, 1901.) 



palatonarial border is produced aft to a plane beyond the middle of the zygomatic foramen. The 

 basicranial axis is moderately shallow. The glenoid articular surface is narrow anteroposteriorly and 

 wide transversely, and the basicranial region is much foreshortened. The bullas, which are the 

 smallest known in the genus, are conical and are delimited between the anterior and posterior 



Fig. 90. — Promerycochcerus 7nacrostegus (Cope). Right half, inferior view of skull. HT. Cat. No. 7444 A.M.N.H. 



1/3 nat. size. (Redrawn from Matthew, 1901.) 



margins of the postglenoid process. The mastoid and paroccipital processes do not completely close 

 the auricular fossa below but do approach nearly to the postglenoid tubercle, which is wide and 

 robust, with height and thickness equal. The paroccipital processes are relatively small, as are also 

 the occipital condyles. There is a marked convexity above the foramen magnum which is separated 

 from the posterior temporal angles by well-defined lateral fossa;, which, however, are much smaller 

 and not so deep as in P. chelydra latulens. Index: 0.65. 



