Established on the upper true molar series of the right side.
This species is intermediate in size between _H. agrarius_ and
_H. modestus_. As in the latter species; the basal ridge extends
around the entire crown of the tooth, with a small interruption on
the antero-external lobe. It is more pronounced, in front and less
behind than in _H. imperialis_. The anterior conical buttress is
not nearly so well developed as in _H. imperialis_; the valleys
are wide, and the descending fold from the antero-external lobe is
obscure, scarcely marked at all in the first. The transverse crests
are strongly arched forwards, and the anterior is very much the
longer. The peculiar feature of the species is the position of the
postero-externa, lobe, which is pushed to the posterior aspect of the
tooth; this is carried so far in the last molar that the two external
lobes stand on nearly the same transverse line. The antero-external
lobe is much the highest point in the tooth, and its the first molar
is remarkably sharp. The enamel is considerably wrinkled, but not
nearly so much as in _H. modestus_.
_Measurements._
M.
Length of first molar ·012
Breadth of first molar ·0155
Length of second molar ·015
Breadth of second molar ·017
Length of third molar ·0145
Breadth of third molar ·017
From Cottonwood Creek.
Hyrachyus nanus, Leidy.
Pr. Ac. Nat. Sc., 1872, 20.
Henry's Fork.
Hyrachyus agrarius, Leidy.
Pr. Ac. Nat. Sc., 1871, 229.
Henry's Fork.
Hyrachyus eximius, Leidy.
Pr. Ac. Nat. Sc., 1871, 229.
Cottonwood Creek.