THE MAMMALIA OP THE DEEP KIVER BEDS. 147 



posterior wing-like prolongations of the parietals and supraoccipital are much re- 

 duced. The occipital condyles project much more strongly backward and somewhat 

 more downward. The paroccipital processes are much wider, at least at the base, 

 where they form broad, thin, antero-posteriorly compressed plates. The notch be- 

 tween the postglenoid and posttympanic processes of the squamosal is greatly wid- 

 ened, especially above ; below, it is narrowed by the downward and forward course 

 taken by the posttympanic. This change is accompanied by another in the position 

 of the external auditory meatus, which is " directed posteriorly in a way quite pecu- 

 liar, resembling somewhat the position seen in some of the hogs" (Cope). 



The zygomatic process of the squamosal has a more massive and rugose exter- 

 nal border and its posterior expansion is directed more horizontally and less vertically 

 than in Mesoreodon, and in the latter respect this species departs considerably from 

 the other species of Merychyus. In spite of this difference, there is a very suggestive 

 resemblance between the present species and Mesoreodon in the appearance of the 

 zygoma. The malar is heavier and has greater depth beneath the orbit. The maxil- 

 lary has a shorter but much higher facial portion and the ridge which runs forward 

 from the malar suture is much better marked. In the type specimen, the region 

 about the infraorbital foramen is much injured, but there is some reason to think that 

 the foramen is double, and a facial vacuity is obviously present, and though its shape 

 and size cannot be accurately determined, it was probably small and fissure-like. 



The premaxillaries are coossified and have their anterior faces much flattened; 

 the ascending rami are much shorter than in Mesoreodon and the anterior nares lower 

 and more obliquely inclined upward and backward. The muzzle is relatively broader, 

 but the increase in height of the alveolar portion of the premaxillaries and in breadth 

 of their ascending rami, contracts the narial opening, especially in its inferior portion, 

 where it becomes very narrow. 



The mandible is different from that of Mesoreodon in several important respects. 

 The horizontal ramus is proportionately shorter, but of greater and more uniform 

 vertical depth, tapering less anteriorly ; the chin is straighter and less concave when 

 seen in profile and the incisive alveolus less depressed and procumbent. As in Mes- 

 oreodon, the anterior mental foramen is placed beneath pTs, whether, as in that genus, 

 there is a second foramen underneath m. i, the specimen is too much fissured to show 

 with clearness, though this appears to be the case. The angle projects somewhat 

 below the inferior border of the horizontal ramus and its posterior margin is more 

 thickened and rugose ; on the other hand, it projects more behind the condyle, from 

 which it is separated by a more decidedly marked notch. The masseteric fossa is 

 notably smaller and does not descend so low upon the side of the jaw. 



