142 



the merycoidodontim: 



moderately heavy and rises to a crest nearly as high as the plane of the supraorbital border. With 

 the postorbital bar the arch is U-shaped, and the external edge is neither so heavy nor so rugose as 

 that of P. macrostegus. The nasals extend slightly behind the antorbital margins from a point 

 nearly above the incisors. These bones are posteriorly truncated, very wide at the nasomaxillary 



Fie. 99. — Pro?nerycochcerus suferbus (Leidy). 

 Fragmentary ramus. GCT. Cat. No. 1 1 52 Y.P.M. 

 1/2 nat. size. 



Fig. 100. — Promerycochaerus suferbus (Leidy). 

 Fragmentary ramus. GCT. Cat. No. 1015 3a Y.P.M. 

 1/2 nat. size. 



notch, anteroposteriorly straight, and slightly convex transversely. The pars facialis of the lacrimal 

 is moderately large and subtriangular in shape. The lacrimal fossa is shallow and wide but con- 

 fined to the lacrimal bone. Sometimes the posterior half is very rugose and the anterior half very 

 smooth. The frontals are unreduced, wide, flat, and somewhat decurved above the medium-sized, 

 nearly circular orbits. The face is moderately narrowed in advance of the orbits. The temporal 



Fig. 101. — Protnerycochoerus suferbus (Leidy). 

 Crown view of inferior molars. GCT. Cat. No. 

 10153a Y.P.M. 2/3 nat. size. 



Fig. 102. — Prcmierycocharus suferbus (Leidy). 

 Fragmentary ramus with posterior three premolars. 

 GCT. Cat. No. 10153 Y.P.M. 2/3 nat. size. 



ridges unite just aft of the postorbital constriction to form a high, thin sagittal crest about a fourth 

 of the length of the skull. The superior skull contour slopes more steeply from the sagittal crest 

 than it does in P. macrostegus. The supraoccipital crest is well produced aft, and the wings are 

 moderately expanded, although farther apart than those of P. macrostegus. The brain case is wide 

 but low, with the lateral ridge more prominent at its anterior portion. The external auditory 

 meatus is moderately large and is directed somewhat backward and upward. The basicranial axis is 

 steep. The palate is medium in width, nearly flat anteriorly, and vaulted aft. It is not posteriorly 

 notched, and the U-shaped palatonarial border is well aft, nearly under the postorbital constriction. 



