124 



THE merycoidodontim: 



slenderer than normal, and the posterointermediate crest extends somewhat more obliquely backward 

 than normal but divides the posterior basin as usual. P 2 is somewhat wider in proportion to length 

 than is P 3 . Index: 0.88. 



Discussion: While these premolars differ in certain respects from the norm in this genus, yet 

 basically they are nearer to this genus than to any other, and I believe that the differences are not 

 of higher than specific value. I do not hesitate to consider this as a form of Promerycochcerus. 



Fig. 80. — Promerycochcerus hesperus Stock. Right ramus and crown view of dentition. 



1/2 nat. size. (After Stock, 1930.) 



HT. Cat. No. 27003 U.C.M. 



Promerycochcerus hollandi Douglass 1907 

 Fig. 8 1 ; PL X, fig. 2; PI. XV, figs. 4-5 



Original Reference: Some new merycoidodonts. Ann. Carnegie Mus., IV, p. 106, pi. XXVIII. 



Type Locality: Canon Ferry on Missouri River, about 20 miles east of Helena, Montana. 



Geologic Horizon: Lower Miocene (lower Harrison). 



Type: Holotype, Cat. No. 1194 CM., skull with badly damaged superior surface; also nearly complete 

 mandible, cervical vertebras, humerus, greater part of front foot, and hind limb, including pelvis. Collected by 

 E. Douglass in 1902 and named in honor of the late Dr. W. J. Holland. 



Specific Characters: The skull is of about the same length as that of P. chelydra and is 

 nearly as wide. The maximum width of the zygomata is opposite the glenoid surface. The malar is 

 deep and extends aft below the squamosal process to the middle of the zygomatic foramen. The 

 posterior part rises abruptly. The nasals extend well forward, but the posterior part has been 

 destroyed, as have the frontals. The lacrimal fossa was apparently shallow and not extensive. The 

 orbits are small. The temporal ridges unite above the anterior of the glenoid surface. The sagittal 

 and supraoccipital crests are lost. The brain case is very small and narrow. The small external 

 auditory meatus is directed upward and backward. The basicranial axis is moderately shallow. The 

 palate is wide and shallowly vaulted, with the U-shaped palatonarial border opposite the posterior 

 end of M 3 . The glenoid surface is narrow anteroposteriorly but very wide transversely. The post- 

 glenoid process is stocky but not very deep. Its external border is nearly vertical. The bulla is 

 small, is oblong in shape, and does not extend in advance of the postglenoid process. The par- 

 occipital processes are broken away. Index: 0.68. 



Mandible: The profile of the chin is very concave, and the mental tubercle is very promi- 

 nent. The symphysiodental angle is 50°. The inferior border of the horizontal ramus is straight, 

 and the angle is barely marked. The condyle is transversely very wide and is gently convex in the 



