TRANSACTIONS OF WAGNER 

 70 



UINTA SELENODONTS 



low groove. In Leptomcryx this bone is as long and quite as broad, but 

 appears to be narrower because of the convexity of its ventral surface. The 

 exoccipitals are low and wide, narrowing dorsally; as in Protylopus, they 

 form a broad prominence above the foramen magnum, with a fossa on each 

 side of it ; the condyles are quite large, expanded laterally, but depressed 

 vertically ; in the median ventral line they are separated by a broad, shal- 

 low notch. The paroccipital processes are laterally compressed and broader 

 than in Protylopus, but, as in that genus, they stand well in advance of the 

 condyles, enclosing large fossae with them. In Leptomeryx the processes 

 have the same shape as in Camelomeryx, but are somewhat smaller and 

 placed farther back. The supraoccipital would seem to have resembled that 

 of Leptomeryx and to have had about the same extension upon the roof of 

 the cranium ; the lambdoidal crest is quite prominent in both genera. A 

 considerable strip of the periotic is exposed between the exoccipital and 

 squamosal, but does not give rise to any distinct mastoid process. 



The basisphenoid resembles the basioccipital in shape, save that it is 

 somewhat narrower. The alisphenoid is quite large ; its ascending process 

 forms a considerable portion of the floor of the cerebral fossa, rising in front 

 to make part of its anterior wall. This bone is so exactly like that of Lepto- 

 meryx in shape that I may apply to it the description elsewhere given of the 

 latter: "The alisphenoid is directed nearly horizontally, but there is a 

 curious angulation or ridge in it, from which a portion of the bone passes 

 upward, bounding the anterior edge of the temporo-sphenoidal lobe of the 

 cerebrum." ('91c, p. 346.) However, in Leptomeryx this angulation is slightly 

 more pronounced. In none of the specimens is the tympanic preserved, and 

 the periotic is thus exposed to view ; the fossa shows, however, that the bulla 

 must have been very small, smaller even than in Leptomeryx, and the con- 

 tracted space between the postglenoid and posttympanic processes of the 

 squamosal indicates an auditory meatus of small size, much smaller than in 

 Protylopus. 



The parietals are very long and narrow, forming almost the entire roof of 

 the cerebral fossa. For their entire length they unite to form a thin but promi- 

 nent sagittal crest, which is far longer than in Leptomeryx, in which the tem- 

 poral ridges are continued over upon the parietals, thus shortening the crest. 

 In this respect both Leptoreodon and Protylopus are more like the White River 

 genus. The parietals are even longer and narrower than in Leptomeryx, and 

 differ from those of the latter in not diverging anteriorly to receive the 



