1915.] Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 335 
and the relative proportions of the teeth, and in one or two cases by pre- 
molar characters of rather doubtful constancy. An effort has been made to 
hold as many of the old names and to create as few new ones as possible. 
Phenacodus primevus Cope, 1873. 
Palexont. Bull., No. 17, 1873, .p. 3; 1885, Tert. Vert, p. 435, pll. Iviib-lviii. 
Syn. P. omnivorus Cops, 1874. 
P. trilobatus Corr, 1881. 
P. nunienus Copp, 1885 (in, part). 
Type of species and genus, Amer. Mus. Cope Coll. No. 4408, a somewhat 
worn and weathered last lower molar, from the Knight formation ! of the 
Wasatch group, on Bear River, near Evanston, Wyo. 
So far as | am aware no other specimens of the genus, than the one 
P. vortmant 
(Topotype, Lost Cabin 
beds, Wind River basin, 
Wyo.) 
P. brachypternus - * 
(Topotype, Gray Bull 
beds, Bighorn, basin, 
Wyo.) 
Fig. 4. Upper teeth of species of Phenacodus. 
- recorded above, have ever been found in the type locality, and for purposes 
‘of comparison it has been necessary to select one of Cope’s supplementary 
types from another region. The splendid skeleton from the Bighorn basin, 
identified by Cope and very thoroughly described and figured in the Ter- 
tiary Vertebrata, offers a most satisfactory plesiotype. The skeleton is 
from a horizon, the Gray Bull, which is probably a stage lower than the 
Knight beds but there is almost perfect agreement between the type and - 
the corresponding tooth of the plesiotype, so that, in the absence of more 
complete material from the type locality, the Bighorn basin skeleton must 
be considered as identical with the type. In the extensive collection of 
Phenacodonts, a form may be seen to 1un through several faunal stages 
without alteration in specific characters. : 
P. primevus is the largest and commonest of the species of Phenacodus. 
1 See Veatch, 1907, U. 8S. G. S., Prof. Paper No. 56, p. 92. 
