324 Bulletin American Museum of Natural History. [Vol. XXXIV, 
Lost Cabin horizon, at Beaver Creek divide, south of the Wind River basin, 
No. 14967, the other from the typical Lost Cabin beds, No. 14617. The 
latter is smaller but otherwise shows the progressive character of the species. 
Other fragmentary specimens are of doubtful reference. 
~ The characters of limb and foot bones have been indicated in the generic 
diagnosis of Hyopsodus. Except in size and robustness I do not observe 
any specific distinctions in the skeleton parts from H. paulus as described 
in the Bridger memoir. 
Hyopsodus wortmani Osborn 1902. 
Hyopsodus wortmani Osporn, 1902, Bull. A. M. N. H., Vol. XVI, p. 185, fig. 11; 
Loomis, 1905, Am. Journ. Sci., Vol. XIX, p. 421, fig. 5. 
Type, No. 4716, upper and lower jaws from the Wind River basin, 
Wyoming. . : 
The lower molars are narrow and elongate, the heel of ms; long, ‘with 
entoconid well separated from metaconulid, and the last upper molar is 
larger than in H. miticulus, the size of its hypocone varying but more 
frequently large. The premolars are distinctly more progressive, p? more 
quadrate in outline, with deuteroconid and deuterocone relatively larger 
than in the older species. From H. mentalis it is distinguished by smaller 
size and less robust form of teeth. 
This form is common in the Lost Cabin horizon of the Wind River basin. 
while in the Lysite a smaller form, probably a subspecies, is found, and has 
been named H. minor by Dr. Loomis. 
This species and H. mentalis are closely elated to the Bridger species, 
H. minusculus and H. paulus respectively. The distinctions are not clear, 
although the Middle Eocene species average more progressive. 
Hyopsodus wortmani ?minor Loomis 1905. 
A lower jaw from the Lysite level in the Wind River Valley and another 
from the same horizon in the Bighorn basin indicate a little Hyopsodus 
close to H. wortmani in tooth characters, but of smaller size, the molars 
only 10 mm. In its relatively narrow, high cusped teeth, long heel of ms 
and well separated metaconid it is very different from sumplex with which 
it agrees in size. 
Loomis’s type of Hyopsodus minor came from the same locality and level 
as these Wind River specimens and agrees in size; but Loomis describes 
the teeth as “short,” whereas in these specimens, as in wortmani, they are 
unusually long. The identification is therefore questionable. 
