J78 
rn ENA COD us. 
Phenacodus omnivorus, Cope. 
Plate xlv, fig. 6. 
Eeport Foss. Vert. New Mexico, U. S. Geog. Survs. W. of 100th M., 1<S74, p. 11; Id.-, 
Ann. Eeport U. S. Geog. Survs. W. of 100th M., 1874, p. 123. 
This quadruped is represented in the collections by a single superior 
molar tooth, which occupied either the last or penultimate position in the 
jaw. Besides being of much smaller size than the corresponding tooth in 
the Phenacodus primcevus, it differs miudi in the composition of its parts. 
Thus, the anterior outer tubercle is obsolete, and the anterior inner is a part 
of the cingular development. The posterior inner is relatively twice as 
large as in P. primcEvus, where it equals the anterior inner. The interme¬ 
diate tubercles (except the external), and the cingulum, are more largely 
developed than in the larger species. 
Superior molar with low and broad tubercular crown, with outline of 
base parallelogrammic, with the external end oblique; the oblique end with 
two principal low tubercles, which form the extremities of two series of 
similar ones, some of wliich arise from the strong cingulum which forms part 
of the summit of the crown. Crown without cingulum on the outer side 
only; elsewhere very strong and crenate, at the inner anterior angle rising 
into a stout, low tubercle. The largest tubercle is near this, on the inner 
anterior summit of the crown, and is connected with the larger or anterior 
outer by a low, broad tubercle. A smaller one intervenes between the cin¬ 
gular tubercle and the smaller external. The outer tubercles low and broad, 
a smaller one opposite the internal between them in the position of a cingu¬ 
lum. Enamel coarsely rugose. 
Measurements. 
M. 
Transverse diameter.. 0. 014 
Longitudinal diameter... .... 0. 010 
Distance between the apices of the inner and outer tubercles.... 0. 007 
Elevation of the cingulum. . . 0. 004 
Elevation of the outer cusp.. 0. 005 
The tooth described is about the size of the posterior inferior molar of 
the Black Bear ( Ursus nniericanus). 
