Douglass — New Species of Merycochcerus in Montana. 433 



separated by an angle. The anterior faces are separated by an 

 excavation l-5 cm wide while the posterior ones are 3 cm apart. 



The basi-occipital and basi-sphenoid ascend at a steep angle. 

 This with the upper contour of the skull makes the brain cavity 

 very small. Beneath the forehead the basi-sphenoid bends for- 

 ward and becomes nearly parallel with it. The basi-sphenoid 

 is angulate for a short distance between the glenoid surfaces. 



The paroccipital processes are broken off at about a level 

 with the lower points of the occipital condyles, but they appear 

 to have been much longer. They are broad transversely but 

 rather narrow antero-posteriorly. At the bases they are nearly 

 crescent-shaped in cross-section. The more convex portion 

 faces inward and backward, while the concave area faces for- 

 ward and outward. The outer portion is a wing-like expansion 

 of the more robust inner part, which slants forward and outward 

 from the occipital condyles, forming with them an angle of 

 65°. The anterior inner horns or lobes are in a line with the 

 post-glenoids. Just in front of these horns and closely in con- 

 tact with them at the bases but with their anterior bases higher 

 are the prismatic tympanic bullae. These bullae are not inflated 

 but quite long vertically, especially on the anterior inner side, 

 and do not extend much below the posterior bases of the par- 

 occipitals. The shape of these bullse is nearly that of a quarter 

 of a cylinder terminated by a cone, the angle joining the nearly 

 plane or slightly concave faces being directed outward and 

 backward. 



The post-glenoid processes are of moderate length and trans- 

 verse breadth, are flat behind and moderately convex in front. 

 The outer border slopes outward and upward, dying out on the 

 inferior posterior surface of the zygomatic arch, which slopes 

 upward and backward from the glenoid surface. This surface 

 is slightly concave, being bounded exteriorly by the ridge on 

 the lower outer border of the arch. The glenoid surface is 

 broad transversely (6 cm ) and uniformly convex antero-poste- 

 riorly. 



The posterior angle of the zygomatic arch is on a line with 

 the anterior borders of the paroccipital process, and extends 

 upward to the line of the lower border of the orbit. 



The malar has four approximately equal sides if the upper 

 is measured along the border of the orbit ; though the lower is 

 longer in a straight line. The vertical width below the orbit 

 and the antero-posterior length just below it are nearly the 

 same. The upward extension in front of the orbit is narrower 

 than the post-orbital process. 



The palatines and pterygoids extend about 2*9 cm back of the 

 last molars. It is only 2 cm from the posterior edges of the 

 pterygoids to the anterior faces of the otic bullse. This 



