Again, the skeleton of Anchitherium is extremely equine.  M. Christol goes so far as to say that the description of the bones of the horse, or the ass, current in veterinary works, would fit those of Anchitherium.  And, in a general way, this may be true enough; but there are some most important differences, which, indeed, are justly indicated by the same careful observer.  Thus the ulna is complete throughout, and its shaft is not a mere rudiment, fused into one bone with the radius.  There are three toes, one large in the middle and one small on each side.  The femur is quite like that of a horse, and has the characteristic fossa above the external condyle.  In the British Museum there is a most instructive specimen of the leg-bones, showing that the fibula was represented by the external malleolus and by a flat tongue of bone, which extends up from it on the outer side of the tibia, and is closely ankylosed with the latter bone.[3] The hind toes are three, like those of the fore leg; and the middle metatarsal bone is much less compressed from side to side than that of the horse.

[Footnote 3:  I am indebted to M. Gervais for a specimen which indicates that the fibula was complete, at any rate, in some cases; and for a very interesting ramps of a mandible, which shows that, as in the Paloeotheria, the hindermost milk-molar of the lower jaw was devoid of the posterior lobe which exists in the hindermost true molar.]

In the Hipparion, the teeth nearly resemble those of the Horses, though the crowns of the grinders are not so long; like those of the Horses, they are abundantly coated with cement.  The shaft of the ulna is reduced to a mere style, ankylosed throughout nearly its whole length with the radius, and appearing to be little more than a ridge on the surface of the latter bone until it is carefully examined.  The front toes are still three, but the outer ones are more slender than in Anchitherium, and their hoofs smaller in proportion to that of the middle toe; they are, in fact, reduced to mere dew-claws, and do not touch the ground.  In the leg, the distal end of the fibula is so completely united with the tibia that it appears to be a mere process of the latter bone, as in the Horses.

In Equus, finally, the crowns of the grinding-teeth become longer, and their patterns are slightly modified; the middle of the shaft of the ulna usually vanishes, and its proximal and distal ends ankylose with the radius.  The phalanges of the two outer toes in each foot disappear, their metacarpal and metatarsal bones being left as the “splints.”

The Hipparion has large depressions on the face in front of the orbits, like those for the “larmiers” of many ruminants; but traces of these are to be seen in some of the fossil horses from the Sewalik Hills; and, as Leidy’s recent researches show, they are preserved in Anchitherium.