Ancodus (or Hyopotamus, as it has been called) is also Oligocene in range, and its remains have been found in the same countries as have those of Anthracotherium. Both genera are indeed closely allied. Ancodus seems to be a more slightly-built creature. The skull looks weaker, but presents much the same features of organisation. In A. velaunus, a species found in French rocks, a metacarpal of digit I. was present in the manus, while A. brachyrhynchus had a completely five-fingered manus.
The Miocene genus Merycopotamus (from the lower layers of the Siwalik formation in India) is more distinctly selenodont than the forms already discussed. On this ground it has been placed in a separate sub-family. As, however, in other respects it does not depart from the Anthracotherian type of structure, this proceeding seems to be hardly necessary. There are two species known, of which one, M. nanus, is, as its name denotes, a dwarf form.
Fam. Caenotheriidae.—While the last family consisted of animals rather more akin to the Pigs, the present is more Pecorine in its characters. The molars are selenodont; but as in the Tragulidae the premolars are more of the nature of cutting teeth. The dentition, like that of so many of these early Ungulates, is complete, and the canines are not prominent. The feet are four-toed, the lateral toes not reaching the ground.
The principal genus is the Eocene and Miocene Caenotherium. Of this genus there were a considerable number of species all European in range, and of small size—not more than a foot or so in length. Their small size is suggestive of the Chevrotains. In the skull the orbital cavity is nearly or quite surrounded by bone, and the tympanic bulla is large and inflated. A common feature of Artiodactyles, a failure of the nasals and maxillae to meet at the side of the face, is to be seen in this ancient forerunner of the Pecora.
Plesiomeryx, also European, and from the same geological horizon, is a very closely allied form.
Fam. Xiphodontidae.—This family consists of slender, small Artiodactyles which are, like the Caenotheriidae, related to the Pecora. They are confined in their range to Europe.
The type genus Xiphodon has selenodont molars and elongated, slender, cutting premolars. The dentition was complete and the canines not highly developed. Like Caenotherium,
