264 
PERISSODACTYLA. 
Hyracotherium vasacciense. Cope. 
Plate Ixvi, figs. 7-11. 
OroMppns vasaceiensis, Cope, System. Cat. Vert. Eocene New Mexico, U. S. Geog. Suits. 
W. of 100th M., 1875, p. 21. 
Lopliiotherium vasacciense, Proc. Amer. Philos. Soc., 1872, p. 474. 
Ten individuals from our collections are referred to tins species, some 
of which embrace portions of both jaws. 
Selecting as type a left mandibular ramus which supports the five 
posterior molars (the last broken), it may be observed that the third pre- 
molar has a strong median cusp, with a small accessory one on its inner side, 
and a similar one immediately in front of it. The posterior base of the 
crown is expanded, and supports a single obtuse cutting-edge of little eleva¬ 
tion. The only cingulum of the tooth bounds the outer and inner sides of 
this part of the crown. The fourth premolar is similar, except that the two 
median cusps are subequal, the anterior one much reduced, and the general 
form stouter. It differs from the first, true molar in the presence of a single 
posterior low cusp, which connects with the anterior by an oblique ridge. 
The opposite cusps of the true molars are well separated by fissures, and 
the anterior ledges are but slightly developed. External cingula well 
marked; enamel wrinkled where not worn. 
Measurements. 
M. 
Lengtli of the five posterior molars.—. 0. 044 
Length of the last two premolars. 0. 013 
Length of the last two molars. 0. 022 
Length of the penultimate molar. 0. 0085 
Width of the same. 0.0070 
Depth of the ramus at the last premolar. 0. 0200 
Depth of the ramus at the last molar. 0. 0220 
In a specimen with the last two superior molars, the rather coarse 
wrinkling of the enamel is visible on the external face, although the teeth 
are well worn. The external tubercles are compressed cones connected by 
a ridge at the base. The accessory anterior external cusp is moderately 
developed. The cingula are distinct, but not prominent, on both the inner 
and outer sides. * 
