PROMKRYCOCHCERUS 



107 



Specific Characters: The skull is about the length of P. vantasselensis but is the most brachy- 

 cephalic of all of the species of the genus. It is almost as wide as long, with the maximum expan- 

 sion of the zygomata opposite the glenoid articular surface. The malar is moderately deep and heavy 

 below the orbit and extends to a plane through the postorbital constriction. The squamosal portion 

 is unique in its extreme descent below the plane of the teeth. It is very heavy and rugose, rising 

 vertically at the glenoid surface and then turning forward and inward to end in a blunt point con- 

 siderably below the level of the unusually high sagittal crest. As is generally found in this genus, 



Fig. 68. — Promerycochatrus carrikeri Peterson. Superior view of skull. HT. 



(Redrawn from Peterson, 1914.) 



Cat. No. 1080 CM. 1/3 nat. size. 



the sutures of the specimen are for the most part obliterated. The nasal bones are transversely 

 convex and have a long, very shallow anteroposterior concavity. These bones are produced beyond 

 the incisive border. The premaxillaries are very short but broad, appear to be extremely truncated, 

 and have an almost vertical position against the maxillaries. The lacrimal fossa; are well marked, 

 shallow, and relatively small. The frontals are moderately short anteroposteriorly, are sharply ele- 

 vated posteriorly, and have a deep triangular pit located medially at the junction of the temporal 

 ridges. Above the orbits the frontals are much inflated and decurved, while anteriorly they narrow 

 gradually. The small orbit is subround in outline. The temporal ridges unite rapidly to form a very 

 high, thick-edged sagittal crest, about a third of the skull length. The supraoccipital crest is 

 produced to a point above the posterior edge of the relatively small occipital condyles, and the wings 

 are nearly transverse. These lambdoidal crests rapidly contract below the crest. The brain case is 

 very small, with the usual prominent lateral ridges, and the whole parietal area is small in both 

 diameters. The medium-sized external auditory meatus is directed upward and outward and is 

 rather highly placed. The basicranial axis is gently curved. The transversely broad palate is gently 

 concave, while the V-shaped palatonarial border is opposite the posterior of M 3 , although it may be 



