with Descriptions of Neiv Species. 233 



vertical diameter of orbits slightly greater than trans- 

 verse; zygomatic arch shallow V-shaped; infra-orbital 

 foramen above P^ ; bullae relatively small, and triangular 

 in basal outline; palate moderately produced poster- 

 iorly; no internal cingulum on superior molars. 



The specimen selected as the type consists of a skull of 

 which the portion anterior to P^ is broken away. The 

 teeth are much worn and the sutures nearly obliterated, 

 due to old age. The skull is, however, remarkably well 

 preserved. 



This species resembles P. clielydra in its great width. 

 The total skull length is slightly greater than that of 

 P. macrostegus, or approximately 385 mm., while the 

 bizygomatic diameter is 278 mm., or more than 13 per cent 

 greater than in that species. The malar below the orbit 

 is flat and directed somewhat obliquely outward and 

 downward. Its width in P. macrostegus is 38.5 mm. ; 

 in P. clielydra, 40 mm. ; in P. superhus, 38 mm. ; and in 

 P. latidens, 58 mm. The malar of P. clielydra is gently 

 concave, while the lacrymal fossse are less deep and 

 smaller than in the latter species. The orbits look chiefly 

 outward and but little forward or upward, thus differing 

 from the position of those in P. clielydra, where they are 

 even more oblique than in P. superhus. 



The anterior part of the squamosal is inserted into the 

 malar below the posterior half of the orbit, whereas in 

 P. clielydra it is not protuberant below the orbit. The 

 apex of the squamosal portion of the zygoma is much 

 beloAV the level of the sagittal crest, but in P. clielydra it 

 is nearly on a level with the crest. This posterior section 

 rises much less vertically than in P. macrostegus, but the 

 outer edge is rounder and heavier than in the last named 

 species. The inferior edge of the malar below the orbit 

 is thickened, quite rugose, and offset from the alveolar 

 parapet a distance of 24 mm. ; that of P. clielydra is thin 

 and slightly convex downward. From below the post- 

 orbital bridge to the glenoid process, the malar forms 

 a sharp ridge, more pronounced than in any other John 

 Day form. It is continued as a ridge of the maxillary 

 to opposite the middle of the second molar, and thence 

 forward as a convexity, dividing the side of the face into 

 two concave portions. The postorbital bridge is wider 

 and heavier than in P. macrostegus. 



The cranium is wide and the sagittal crest high and 



