88 Bulletin American Museum of Natural History. [Vol. XXXIV, 
horizons of the Wyoming Wasatch. It has not been found in the Clark 
Fork beds, and a single tooth is the only representative from the Sand 
Coulée beds. Dr. Loomis, however, reports finding it in the upper levels of 
the Big Horn Wasatch. 3 | ; 
From the Gray Bull beds a number of skulls, jaws and skeletons all in a 
eae ae; a, ‘ iS on 
se Gs Say ae 1a S 
tI 
P. gigantea 
M2—p3 
P. ponderosa 
Me—-p4 
Fig. 78. Pachyena, lower teeth of four species, outer views, half natural size. All from 
Gray Buil beds, Big Horn Basin, Wyoming. 
more or less fragmentary condition have been secured by the various expedi- 
tions, and the osteology of the type species is fairly well known from the 
material now at hand. Three well distinguished species are represented, 
which agree approximately both in size and proportions with the three 
generic types of the Middle Eocene — Harpagolestes, Synoplotherium and 
Mesonyx. It seems probable that these three species of Pachyena are 
ancestral to the three Bridger genera, but in the absence of mtermediate 
links it cannot be regarded as proven. 
The tetradactyl manus and pes sharply distinguish this genus from 
Dissacus saurognathus. In 1909 I stated with regard to P. ossifraga that: 
“The number of digits is not certainly known, but the structure of limb 
bones and foot bones as well as of the teeth is so much more like that of 
Mesonyx than of Dissacus, that there is little doubt that the feet were 
