The _astragalus_ has narrow and very oblique condyles, which are more equal in size than in _Orohippus_; the neck is very short, the internal condyle reaching to the face for the navicular; the posterior projection of this condyle is much shorter than in that genus. The articular face for the navicular is quadrate in shape and concave; the cuboid face is very narrow. The articulation with the calcaneum is made by a narrow, convex face. When the two are in position the navicular face of the astragalus is in the same horizontal line as the cuboid face of the calcaneum, thus resembling the arrangement of the horse's tarsus rather than that of _Orohippus_. The calcaneum is a short, slender bone, having the upper and lower margins convergent toward the tuberosity, and not parallel as in _Orohippus_. The tuberosity is especially small. The face for the cuboid is very narrow. From the articular facets of these two bones we can see that the tarsus resembled very much that of the modern horse, with a broad, short navicular, and a narrow cuboid. The strata in which these remains were found were somewhat higher than those containing the bones of _Orohippus_. _Measurements._ M. Greatest length of astragalus 0·021 Greatest breadth of ditto ·018 Length of neck of ditto ·005 Width between the condyles ·010 Vertical diameter of face for navicular ·012 Transverse diameter of ditto ·012 Length of calcaneum ·046 Width of face for cuboid ·006 From Henry's Fork. OROHIPPUS, Marsh. Am. Jour. Sc. vol iv., p. 207, third series. _Generic Characteristics._--"The crowns of the upper true molars are composed of a pair of external cusps similar to those of anchitherium. There are two corresponding inner tubercles, from which ridges extend obliquely to the anterior inner margin of the outer cusps; but the anterior ridge is divided so as to form an intermediate anterior tubercle. All the teeth preserved have a distinct basal ridge." _Species Known._-- Orohippus pumilus, Marsh. Orohippus major, Marsh. Orohippus agilis, Marsh. Orohippus gracilis, Marsh. Orohippus pumilus? Marsh. Specimen obtained. Penultimate and third superior molars, with part of zygoma. From Cottonwood Creek. Orohippus major? Marsh.