431 Douglass — New Species of Merycochoerus in Montana. 



approximation is due to the extreme shortening of the posterior 

 basal elements of the skull so that the post-glenoid and par- 

 occipital processes, the occipital condyles and otic bullae occupy 

 a comparatively narrow transverse zone. 



Between the posterior lobes of the last molars the palato- 

 pterygoid lobes extend downward and backward until they 

 reach a point about on a level with the incisive border and the 

 lower extremities of the occipital condyles. They formed a 

 median trough extending downward and backward from the 

 palate. 



.- 



Merycochcerus laticeps. 

 Skull, view of under side, nearly x f. 



Lower Jaw. — The rami were not coossified at the symphysis, 

 and in the present specimen they are slightly spread apart. 

 The anterior border is concave downward and nearly uniformly 

 convex transversely. The foramen mentale is beneath jpm 3, 

 as is also the angle of the chin. At this angle a small process 

 projects downward. Back of this the lower border of the ramus 

 curves slightly upward and then downward to a point beneath 

 the posterior part of m 3. At this point it is twice the depth 

 of the shallower part under m 1. Back of this the posterior 

 border ascends with a steep curve to a point 4:'5 cm below the 

 top of the condyle, where it ascends nearly vertically to the 

 condyle, forming a low angle (about 25°) with the continuation 



