32 Bulletin American Museum of Natural History. [Vol. XIV, 



With the skull were found a few fragments of the skeleton. A 

 humerus resembles that of Arctocyon, but is smaller and shorter, 

 deltoid crest hardly as prominent, supinator crest somewhat 

 more so, distal trochlea wider but quite as deep. The form of 

 the distal trochlea approximates that of Pantolambda and Perip- 

 tychus, but the bone is smaller and slenderer than in either of 

 these, the skulls being of nearly equal size. 



Pachyaena gigantea O. 6^ IV. 



" Founded upon a series of finely preserved upper cheek teeth lacking only 

 the first premolar. The specific distinctions from P. ossifraga are very 

 marked— (a) the presence of a metacone upon the third upper molar ; (b) the 

 more complex structure of the third and fourth premolars ; (c) the very broad 

 crenate external cingulum ; (d) the relatively smaller size of the metacone in the 

 molars." — Osborn dr" Wortman, 1892, p. 113. 



This is one of the largest of the Creodonta, being exceeded in 

 size of skull only by some undescribed specimens of Mesonyx in 

 the Museum collections. Hemipsalodon grandis Cope, though 

 much larger in skeleton/ seems to have had a somewhat smaller 

 skull.* Part of a skull and jaws (No. 2823) and a fragmentary 

 skeleton (No. 2959) are here described. Both are from the 

 Wasatch beds of the Big Horn Valley, Wyoming, collected by 

 the Expedition of 1896. 



The skull preserves the second premolar and third molar, and 

 alveoli of all the upper teeth except the incisors, also most of one 

 ramus of the lower jaw. The fragmentary skeleton includes 

 parts of the upper jaws with the molars in place, and parts of 

 the lower jaw with the molars in position and the canines and 

 third premolar emerging from the jaw. With it are several loose 

 teeth, most of the limb bones, but all more or less broken, the 

 astragalus and calcaneum and several vertebrae. The epiphyses 

 are missing from the majority of the bones. 



Upper Teeth. — First premolar one-rooted, the second and third 

 two-rooted and simple crowned, the fourth three-rooted, molari- 

 form, with two well separated cusps of equal size and a widely 

 separated internal cusp. Its peculiar shape, small size, and un- 

 usual wear suggest that it is a persistent milk tooth ; this view is 

 strengthened by the fact that the corresponding premolar in the 



' If the femora referred to it by Professor Cope really belong to the species, which I consider 

 very doubtful, as the proportion of skull and body would be most unusual for a Creodont. 



