The specimens which so far have been found in the American middle and upper Miocene and lower Pliocene are very fragmentary, consisting of little more than teeth, and give no information other than to demonstrate the presence of the family in North America during that period of time. On the other hand, the European genera of the middle Miocene and lower Pliocene are well known and may or may not have been closely similar to their American contemporaries, though they were undoubtedly larger. In these most peculiar and grotesque animals (_†Macrotherium_ and _†Chalicotherium_) the head was relatively small, the teeth were very low-crowned and adapted only to a diet of soft vegetable substances and the mode of feeding must have been that of browsing upon leaves and shoots of trees and bushes; the premolars had not acquired the molar-pattern, which was very exceptional for perissodactyls of so late a time, such a difference between the two classes of teeth being characteristic of the Eocene members of the order; the incisors and canines were reduced, but the formula is not definitely known. The neck was of moderate length, the body very long, and the limbs were also elongate, especially the anterior pair, in consequence of which the back sloped downward from the shoulders to the rump; the two fore-arm bones were fused together, and these, with the thigh-bones, were the longest segments of the limbs. The special peculiarity of these animals was in the character of the feet, which had three toes, each armed with a huge claw, instead of terminating in a hoof, as it does in all normal perissodactyls. The external digit, which, in the absence of the fifth, was the fourth, was the largest of the series and apparently bore the most of the weight, a notable departure from the normal perissodactyl symmetry, in which the third or median toe is the largest. The hind feet were considerably smaller than the fore, but had similar claws.