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 UINTA SELENODONTS 



but high and conspicuous sagittal crest, which is not so straight as in Oreodon, 

 but is arched from before backward, much as it is in Agriochcerus. The squa- 

 mosal is very large and forms much the greater part of the cranial wall, though, 

 corresponding to the broader parietal, it is somewhat narrower than in Oreodon. 

 The glenoid cavity and process are typically oreodont, though the process is 

 somewhat smaller and less massive than in the White River genus. The zygo- 

 matic process, which is shorter than in 0. atlbertsoni, curves out boldly from 

 the side of the skull, but is slender and pursues an almost horizontal course, 

 not arching upward and then downward nearly so much as in the White River 

 forms. The jugal, on the contrary, is longer than in the latter and extends 

 much nearer to the glenoid cavity ; it is very slender and is not notched to 

 receive the zygomatic process as it is in Oreodon, and the postorbital process 

 is so feebly developed that the orbit is even more widely open behind than in 

 Agriochoerits. As a whole, the zygomatic arch is more elongate, more slender, 

 and much more nearly horizontal than in Oreodon, in which the arch descends 

 quite strongly anteriorly, a feature which is due to the increased height of the 

 ascending ramus of the mandible. 



All of the skulls which I have examined are more or less damaged in 

 front of the orbit, rendering it impossible to make out the limits of the lach- 

 rymal, though it may be seen, at least in some specimens, that the lachrymal 

 pit, which is so characteristic of the later members of the family, is not present. 

 A difference from Oreodon may be observed in the frontals, which descend 

 forward at the forehead and are flat, not swollen and arched by the large 

 sinuses. The forehead is 'broad and lozenge-shaped, narrowing abruptly be- 

 hind and gradually in front, and displaying obscurely marked temporal ridges. 

 The postorbital processes are in P. parvus quite long and decurved, much 

 shorter in P. paradoxiciis. The nasals are long, narrow, and quite convex 

 transversely ; in front they terminate in points and project well beyond the 

 premaxillse. The anterior nares are small, terminal, and almost vertical in 

 position. 



The premaxillaries are small, and, as in Oreodon, but little of them is 

 visible in side view ; the alveolar portion is low and weak, and in such species 

 as P. paradoxicns, which have reduced incisors, the two bones do not meet 

 in the median line. The incisive foramina are quite large and the spines are 

 long, extending back to pi. I can discover no indication of the curious 

 dorsal expansion of the ascending ramus which in Oreodon is received into a 

 notch in the maxilla. The maxillary is shaped much as in 0. ciUbertsoni, but 



