_Cotylopidæ._—The Miocene genus _Cotylops_ (_Oreodon_[185]) is the type of a large American family in which the upper molars are selenodont and usually have four columns, while the lower canine is approximated to the incisors and its form and function assumed by the first premolar. The last upper premolar is simpler than the molars. There is no flange to the angle of the mandible; and the feet have four digits. The affinities of this peculiar family are probably widely spread, but they may have been derived from the _Anthracotheriidæ_. The type genus has the full Eutherian dentition, but in some of the more specialised forms (_Cyclopidius_) the upper incisors may be wanting, and large vacuities occur in the lachrymal region. The generalised genus _Protoreodon_, of the Upper or Uinta Eocene, has five cusps on the upper molars, arranged as in the _Anthracotheriidæ_. The pollex is retained in the manus of the type genus. [Illustration: FIG. 113.—Restoration of _Anoplotherium commune_ (Upper Eocene). Cuvier.] The family may be divided into subfamilies as follows:— I. Upper molars with four columns. 1. Orbits open, no lachrymal fossa, a diastema, the last upper premolar with two outer columns, outer wall of upper molars concave and inclined inwards.—_Agriochœrinæ_ (_Agriochœrus_). 2. Orbits closed, a lachrymal fossa, no diastema, the last upper premolar with one outer column; outer wall of upper molars flattened.—_Cotylopinæ_ (_Cotylops_, _Eporeodon_, _Merycochœrus_, _Cyclopidius_, etc.) II. Upper molars with five columns.—_Protoreontinæ_ (_Protoreodon_). _Anoplotheriidæ._—This family includes several Upper Eocene European genera, with selenodont upper molars, carrying five columns arranged as those in _Anthracotherium_. One of the earliest known, _Anoplotherium_, was fully described by Cuvier from remains found in the Paris gypsum-beds (Upper Eocene). Its forty-four teeth formed a series unbroken by a gap or diastema, and were of uniform height (as in Man alone of existing mammals). Its tail was long, with large chevron bones underneath, not usually found in Ungulates, and there were either three or two toes on each foot. It was in many respects a much-specialised form, apparently not on the line of descent of any of the existing groups. _Dacrytherium_ is an allied genus whose dentition leads on to that of the smaller _Xiphodon_. The latter genus is characterised by the compressed and elongated form of the crowns of the first three premolars, which thus approximate to those of the Chevrotains. There were only two functional digits to the feet. The so-called _Hyopotamus picteti_, of the Swiss Eocene, is a species of _Dacrytherium_.