THE MAJrMALIA OF THE UINTA FOKMATION. 489 



toreodon. From the crushed condition of this part of the skull it cannot ver}- well 

 be determined whether or not the peiiotic was exposed upon the surface, but in all 

 pi-obability it was. The frontals form but very little of the roof of the cranium, as 

 they terminate just behind the orbits and are chiefly confined to the covering of the 

 orbits and nasal cavity. The supraciliai-y ridges are prominent and diverge from the 

 sagittal crest, as in Oreodon, terminating in long, overhanging postorbilal processes, 

 but. as in A(jriochcerus, they do not leach the jugal and the orbits are widely open 

 behind. 



The squamosals ai-e very large and form most of the side walls of the cranium ; 

 they articulate with the parietals both superiorly and anteriorly. The zygomatic 

 processes are very long ; the free poition is compressed laterally and quite slender, 

 but the bases have a considerable antero-posterior extent, as in Oreodon ; the post- 

 glenoid processes are less massive, and are less produced transversely and more ver- 

 tically than in that genus. The glenoid cavity is also somew^hat different ; Leidy 

 thus describes it in Oreodon (No. 7, p. 75): "The glenoid articulation exhibits a broad 

 surface extending outwardly on the under pait of the posterior root of the zygoma. 

 Its fore part is nearly straight and hoiizontal transversely, and is modei-ately convex 

 antero-posteriorly, inclining forward internally and backward externally. Postero- 

 internally it descends upon a remarkably large and strong postglenoid tubercle, 

 which is antero-posteriorly compressed, mammillary in shape." This description 

 applies also to the glenoid cavity of P/oforeofZo/i, except that the surface has a smaller 

 extent from before backwards, it is rather more strongly convex in front and is not pro- 

 duced into an elevation internally; the postglenoid process is also much less massive. 



In correspondence with the great elongation of the cranium the zygomatic arches 

 are very long; the jugal is long and quite slender and has but a rudimentary post- 

 orbital process, which is widely separated fioin that of the frontal ; it is not notched 

 to receive the anterior end of the zygomatic process, as in Oreodon, and has a some- 

 what greater extension upon the face than in that genus. The lachrymal, on the 

 contrary, would seem to be smaller, and apparently had no depression or pit, though 

 this statement cannot be made positively. 



The base of the skull is unfortunately much injured mikI allows but little to be; 

 made out with regard to its structure. The alisphenoids aie very large and have 

 large pterygoid plates, which bound the much elongated posterior nares ; the latter 

 exteiids far forward between the molars and ends anteriorly in a pointed arch, so that 

 both in shape and position it agrees closely with that f)f . (r/;-/ot'//"'//<s, and is (piile 

 dillerent from that of (freodon. It cannot be ascerLaiued, whelhcr or not the tym- 

 panic bulUe were intluted, but we may infer that they were from the iact that such 



