150 



the merycoidodontim: 



The canine is robust, and its long diameter is somewhat oblique to the sagittal plane. The superior 

 molar-premolar index is 0.78 and the inferior 0.86. 



Skeleton: This animal is smaller and more lightly built than P. carrikerl. The body was 

 about 12 per cent shorter and the limbs and feet relatively shorter still. It possessed long ribs, a 

 long, heavy and deep body, and in general build was somewhat suggestive of the hippopotamus. 



Discussion: The skull of this species possesses a structure which I have not found in any other. 

 About midway between the brain case and the apex of the zygomata, and on the back part of the 

 superior surface of the glenoid process, there originates a ridge of bone which is directed inward and 

 backward. It undoubtedly served as additional surface for insertion of the large neck muscles. 



A.M.I2967 



A.M.I2968 



Fig. 111. — Promerycochcerus vantasselensis fygmtzus Loomxs. Skull and superior dentition. HT. Cat. No. 12967 A.M.N. H. 

 Front foot of PT. Cat. No. 12968 A.M.N.H. 1/2 nat. size. (After Loomis, 1924.) 



Promerycochcerus vantasselensis pygmaeus Loomis 1924 

 Fig. Ill; PI. XX, figs. 2-3 



Original Reference: Miocene oreodonts in the American Museum. Bull. Amer. Mus. Nat. Hist., 

 LI, Art. 1, p. 27, fig. 13 {Promerycochcerus fygmyus). 



Type Localities: Two miles northwest of Post Office, Porcupine Creek, South Dakota. Paratype, three 

 miles northwest of Post Office, same locality. 



Geologic Horizon: Lower Miocene (lower Rosebud). 



Types: Holotype, Cat. No. 12967 A.M.N.H., skull. Paratype, Cat. No. 12968 A.M.N.H., imperfect 

 skull, well-preserved fore feet, and other limb bones. 



Specific Characters: The skull is the smallest of the genus, unless P. hollandi minor proves 

 to be smaller when a complete skull is found. The maximum expansion of the zygomatic arches is 

 near the middle of the zygomatic foramina. The malar is relatively deep, and the convexity forward 



