Douglass — New Species of Merycochcerus in Montana. 431 



On the side of the face is a large depression difficult to 

 define. It is nearly triangular in shape. Above its boundary 

 is the median upper border of the maxillary ; behind it is the 

 outward expansion of the posterior part of the maxillary in front 

 of the orbit. Beneath is a broad shelf above the malo-maxillary 

 ridge. The anterior angle of the depression is occupied by a 

 deeper elliptical one, the deepest part of which is above the 

 last premolar and the first molar. These two concavities 

 extending inward on opposite sides of the maxillaries make the 

 face quite thin transversely in this region, being in fact only 

 24 cm thick, while the skull at its widest place is 20 cm . The malo- 

 maxillary ridge dies out on the anterior border of this depres- 

 sion but expands rapidly posteriorly, thus forming the broad 

 shelf above mentioned which is broadest in front but extends 

 outward and backward toward the zygomatic arch. The infra- 

 orbital foramen is large, is near the inferior posterior border of 

 the oval depression above m® and looks forward and outward, 

 opening on the horizontal maxillary platform or shelf. 



The nasals are nearly triangular if I make out their pos- 

 terior borders correctly. They are short, extending upward 

 and forward to form the roof of the external nareil opening. 

 They are convex transversely and longitudinally and are 

 pointed in front. These points are about midway between the 

 incisor and the inion. 



The orbits are oval with the larger end upward. The pos- 

 terior inferior border is nearly straight or a trifle convex, but 

 this may be due to a slight displacement of the post-orbital 

 process of the malar. Only one orbit is preserved. 



What I take to be the boundary between the nasals and fron- 

 tals is a line where the bone is broken. It passes from the 

 posterior angle of the maxillary transversely and somewhat 

 backward to the suture between the nasals. 



The frontal appears to meet the malar posterior to the orbit 

 at the median line, where there is a roughening on the narrow 

 isthmus of bone. From the upper posterior border of the 

 orbit the supra-orbital ridges converge rapidly backward and 

 then less rapidly, uniting to form a prominent narrow sagittal 

 crest. The form of this part of the skull back of the nasals 

 and including the upper part of the brain case is almost like that 

 figured in Bettany's paper, " On the Genus Merycochcerus," 

 as M. temporalis / but the supra-orbital foramina occupy a 

 different position. In the present species they are above a 

 line uniting the posterior borders of the orbits, are far apart, 

 have no grooves leading into them, and are a little nearer the 

 median line of the skull than the outer border. The tempero- 

 parietal suture extends upward and backward until, beneath 

 the anterior part of the sagittal crest it curves downward and 



