PROMERYCOCHCERUS 147 



between the last molar and the glenoid surface. The glenoid articular surface appears small in 

 comparison with the great expanse of the posterior zygomatic pedicle. It is about twice as long trans- 

 versely as wide, is gently convex, and is at right angles to the sagittal plane. The postglenoid 

 processes are rather small and anteroposteriorly compressed. The bulla; are relatively small, tri- 

 angular in section, and extend forward in advance of the postglenoid processes and downward but 

 not below the level of these processes. The paroccipital processes are robust, contact the bulla;, and 

 approach nearly to the postglenoid processes. They are triangular in section. Index: 0.71. 



Paratype: (Only the characters in which it differs from the holotype are' noted.) The skull 

 is about 7 per cent shorter and 20 per cent narrower. The maximum expansion of the zygomata is 

 just behind the postorbital bar. The malar is proportionally deeper and the squamous portion of 

 the arch very much reduced, without the abrupt outward turn below the postorbital bar. The crest, 

 about on a level with the middle of the orbit, lies above the anterior face of the postglenoid tubercle. 

 The nasals are proportionally shorter, less decurved anteriorly, and posteriorly truncated, and they 

 extend slightly posterior to a plane through the antorbital margins. The lacrimal bone is oblong in 

 the pars facialis, and the antorbital fossa is larger and deeper. The frontals rise anteroposteriorly 

 aft much more markedly, the supraorbital decurvature is much less marked, and these bones extend 

 more anteriorly. The orbits are proportionally larger, the long axis is horizontal, and they are 

 somewhat more posteriorly placed. The temporal ridges unite more quickly, and the sagittal crest is 

 somewhat shorter than a fourth of the skull length. The supraoccipital crest is less produced aft, 

 and the wings are closer together. The brain case is proportionally smaller. The external auditory 

 meatus lies above and in the vertical plane of the paroccipital process. The palate is posteriorly 

 deeply notched, and the U-shaped palatonarial border lies farther aft, about in a vertical plane 

 through the middle of the zygomatic foramina. The glenoid articular surfaces are oblique to the 

 sagittal plane. The bulls are proportionally larger and the postglenoid processes relatively smaller. 

 The inferior surfaces of the bulla; are pitted. The paroccipital processes are more transversely 

 expanded at their bases and somewhat twisted upon themselves. Index: 0.62. 



Foramina: The infraorbital foramen in the holotype is above the anterior part of P 4 and in 

 the paratype above the interval between P 4 and M 1 . In both, the supraorbitals are about 20 mm. 

 apart. The foramen ovale is large. The posterior palatine foramina cannot be discerned in the 

 holotype j they are opposite P 4 in the paratype. 



Dentition: The metastyle of M 3 is large in the holotype and small in the paratype. The 

 internal cingula of the former are faint or interrupted, but in the latter all the molars and P 4 have 

 well-defined internal cingula. The posterior crescent of P 3 is not so well developed as in some of 

 the species, for example P. montanus grandis. P 1 is isolated in the female but not in the male, other- 

 wise the dental pattern is similar in both and typical of the genus. The superior molar-premolar 

 index of the male is 0.80 and of the female 0.93, while the inferior index of the female is 0.937. 



Discussion: From the standpoint of relationship, I should refer the male skull to P. vantas- 

 selensis and that of the female to P. carrikeri. I believe that the two skulls are nearer to those 

 species than they are to each other. 



Promerycochoerus vantasselensis Peterson 1906 

 Figs. 108-110; PI. XLV, fig. 2 



Original Reference: The Miocene beds of western Nebraska and eastern Wyoming and their ver- 

 tebrate faunae. Ann. Carnegie Mus., IV, pp. 36-37, pi. XI. 



Type Locality: Vantassel Creek, Niobrara County, Wyoming. 



Geologic Horizon: Lower Miocene (lower Harrison). 



Types: Holotype, Cat. No. 1230 CM., skull, right ramus, and other parts of skeleton. Paratypes, Cat. 

 Nos. 1232 and 1232A, CM. Plesiotypes, Cat. Nos. 1239 CM., and 20-140 A.M., a mounted skeleton. 

 Name given in allusion to type locality. 



