248 O. C. Marsh—Notice of New Tertiary Mammals. 
narrow and deep. The great tuberosity is elevated, and com- 
pressed. The distal end of the humerus is small. The 
radius and ulna are distinct. The latter is larger than in 
Anchitherium, and entire throughout its whole length. The 
carpal bones are eight in number, and somewhat similar to 
those of the Tapir, ‘although the trapezium is proportionally 
much smaller. 
All the digits of the manus, except the first, are well devel- 
oped, as oT in the accompanying figure of the left fore- 
foot of Orohippus agilis Marsh. The third digit 
is the largest, and its close resemblance to that of 
the horse is clearly marked. The terminal pha- 
lanx, or coffin bone, has a shallow median groove 
in front, as in many species of this group in the 
late Tertiary. The fourth digit exceeds the 
—— in size, and the fifth is much the shortest 
much larger than the second. The astragalus has 
its neck more elongated than in Anchither’um, 
and the face for the cuboid is small. The tibia and fibula are 
distinct. The cervical vertebree of Orohippus are rather short, 
and moderately opisthoccelous. 
oe iit major, ee nov. 
molars. 
Measurements. 
Space occupied by three upper true molars, - ------ cen a ies oe 
Ghana ai Sele of last upper molar, ------- ---- 8°5 
Transverse diam cant 
Antero-posterior ne of penultimate upper molar, ...- 8°95 
eneavrie GONE, Sk. 8 en ie ees 11° 
Extent of four pease teeth of lower jaw, Ban 
Antero-posterior diameter of last lower fk ee 10°5 
— — diam Ne hs oe oa ek 5° 
An or diameter of last lower premolar, -_..- ---- 75 
Depth of ie ase middle of this toot th, GE 
This species was about as large as a fox. The remains of it 
at present known are from the Eocene of Wyoming. 
