Leidy, Proc. Ac. Nat. Sc., 1872, p. 169.--Cont. to Ext. Vert. Faun.
of Western Territories, p. 93.--Cope, Hayden's Survey, 1872, p.
580, etc.
Skull broader proportionally than in the other genera of the order,
ridged and possessing several concavities on the upper surface;
zygomas slender and but little curved; temporal fossæ comparatively
short and have well-defined superciliary margins. The cervical
vertebræ are rather long; the sacrum has four vertebræ; and the tail
is quite long, very flat and broad. The tibia has its proximal face
divided by a prominent ridge into two parts. The dental formula
for the upper jaw is: I. 0, C. 1, M. 6. The molars are small, and
increase from first to sixth. The last is much the largest; in it the
anterior lobe considerably exceeds the posterior in size, and there
may or may not be a tubercle at the entrance of the valley between
the lobes; but there is always one developed from the cingulum at the
posterior part of the tooth.