1915.| Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 343. 
Phenacodus vortmani Cope, 1880. 
_ Copz, 1880, Amer. Nat., p. 747 (Hyracotherium); 1885, Tert. Vert. p. 433, pl. 
Ivii, fig. 9. 
Syn. ?Phenacodus apternus Corr, 1882. 
Type, Amer. Mus. Cope Coll. No. 4824, a left ramus with the ps and a 
damaged m, and the roots of other molars and premolars; Lost Cabin beds, 
Alkali Creek, Wind River basin, Wyo., J. L. Wortman, 1880. 
A very satisfactory topotype is represented by No. 14787, lower jaws 
with all molars and premolars, unworn, and No. 2983, a maxilla with pm’, 
unworn (Figs. 4, 6 and 8). The lower jaws were collected in 1909, the 
maxilla in 1896, both are recorded as coming from the north side of Alkali 
Creek near its mouth and both are from the same distinctive matrix, a light 
gray clayey sandstone, in which fossils are rare. The lower teeth fit exactly 
to the uppers and both show the same slight traces of wear on the first and 
second molars. It is without much hesitation that I consider them as be- 
longing to one individual. | 
Distinctive characters, as shown by the topotype, are, aside from the 
measurements of the teeth, ramus relatively short and deep; p3 with a well 
defined anterior basal cusp, fairly well defined external and internal cusps 
of equal size on the posterior face of the protoconid and an unusually high 
posterior basal cusp; ps without entoconid but with the posterior inner 
angle developed into a low ridge, forming a shallow basin; p* with outer 
cusps of nearly equal size, inner cusp bent slightly forward and with the 
cingulum on the posterior side of the tooth developed into a point, which 
foreshadows the tetartocone; p? with large and small outer cusps and large 
inner cusp, twisted forward away from p‘ and opposite the cleft between the 
outer cusps. | ; 
Occurrence. About 15 specimens from the Lost Cabin are referable to 
this species, chiefly by size alone since most of the specimens consist of molar 
teeth only. From the Lysite three specimens agree in size. J*rom the Gray 
Bull beds five, and one from the lower horizon of New Mexico is doubtfully 
referred. The reference of all specimens not from the type-horizon, how- 
ever, is only provisional. 
Phenacodus apternus Cope, 1882,' from the Gray Bull beds of the Bighorn 
basin, is based on three fragments of lower jaws, each supporting the three 
true molars. The species was based principally upon the “oval form of 
the last inferior molar,” a character in which the three cotypes differ as 
1 Paleeont. Bull., No. 34, p. 180. 
