PHENACODUS. 
173 
pair of the second molar, and the posterior pair of the thii’d. The fourth 
molar is the largest, having an additional or fifth tubercle posteriorly, thus 
inclosing a longer basin than do the borders of the other molars. The 
inner anterior tubercle is the most elevated, and there are no cingula. 
Meas^irements, 
Lengtli of the posterior three molars. 
Length of the posterior molar. 
Width of the same. 
Length of the second molar... 
Width of the same. 
Depth of the ramns at the second molar. 
Diameter of the incieorS ‘■“tero-posterior. 
(transverse .. 
M. 
0. 0112 
0. 0042 
0.0032 
0.0035 
0. 0027 
0. 0104 
0. 0040 
0. 0027 
GENERA INCERTJ5 SEDIS. 
PIIENACODUS, Cope. 
Phenacodns, Cope, Paleontological Bulletin, No. 17, p. 3, 1873; Eeport Vert. Foss. 
New Mexico, U. S Geog. Survs. W. of 100th M., 1874, p. 10; Id., Ann. Re¬ 
port U. S. Geog. Survs. W. of 100th M., 1874, p. 122. 
A genus of Mammals whose affinities it is not yet possible to state 
with certainty, first discovered by myself in the Wasatch beds of Bear 
River, Wyoming, was found not uncommonly in the corresponding horizon 
in New Mexico. 
There are three molars in each jaw, and the specimens include two 
premolars, which form a continuous series, as in AclicBnodon. There are 
four principal tubercles on the inferior molars, and sometimes a third small 
one between the posterior pair, always present on the last one, which is, how¬ 
ever, not largely developed. The first inferior premolar presents a broad 
heel, a double median tubercle, and an anterior tubercle (in P. primmvus). 
The crowns of the superior molars are low and broad, and support numerous 
tubercles; these are low and vary in number, but there are two near the 
external border which are quite constant. They have general resemblances 
to those of Hogs, Bears, and Monkeys. The first true molar is broader 
than long, and there are no diastemata between it and the premolars, or 
between the latter, which are irregularly quadricuspid and tricuspid respect¬ 
ively. The forms of these teeth are entirel}^ different from those of the 
corresponding teeth in ElotJierkim. 
