The Moose, Caribou and Wapiti were unquestionably immigrants and came in not earlier than the Pleistocene. Nothing is known in the Pliocene or more ancient Tertiary epochs of North America which could be twisted into forms ancestral to these typically Old World genera. With the southern deer (_Odocoileus_, etc.) the matter stands differently, for these have a probable American ancestry extending back to the lower Miocene and possibly much farther. On the other hand, it is not altogether certain that these may not have been Pliocene immigrants, for their genealogy is still in an extremely fragmentary and unsatisfactory condition. The North American genus, _Odocoileus_, extended back to the Pliocene with very little change. The annoying, unrecorded gap of the upper Pliocene and the meagre representation of the middle Pliocene mammals given by the Blanco leave us without information regarding the deer of that time. In the lower Pliocene and through the whole Miocene we meet with frequent remains of a genus (_†Blastomeryx_) which was quite probably the ancestor of the American types of deer. It was considerably smaller than any of the existing North American species and had no antlers, but possessed the sabre-like, upper canine tusks, which characterize the muntjacs and hornless deer of Asia. The limb-bones had already attained nearly their present state of development, as regards the reduction of ulna and radius, formation of cannon-bones, etc. _†Blastomeryx_ probably entered North America in the lower Miocene, but, as was mentioned previously (p. 409), Dr. Matthew and Professor Osborn regard the genus as autochthonous and descended from the †Hypertragulidæ. [Illustration: FIG. 221.—Lower Miocene †hornless deer (_†Blastomeryx advena_). Restored from a skeleton in the American Museum of Natural History.] In the middle Miocene _†Blastomeryx_ gave rise to an aberrant genus (_†Merycodus_) which has been made the type of a distinct family (†Merycodontidæ, see table, p. 362), but this is perhaps unnecessary. _†Merycodus_ had deer-like antlers, but completely hypsodont teeth such as no known member of the Cervidæ possesses. The middle Miocene species (_†M. osborni_) was a little creature, not more than eighteen or twenty inches high at the shoulder, and had a branched antler of three tines, which was considerably longer than the skull, while in the species of the upper Miocene (_†M. furcatus_) the antler was shorter and simply forked. From the number of specimens of these animals found in which the burr is incomplete or absent, it may be inferred that the antler was not always deciduous. The legs were long and very slender, and apparently there was no trace of the lateral digits, even in the fore foot. These peculiar hypsodont deer persisted even in the older Pleistocene. [Illustration: FIG. 222.—Miocene †deer-antelopes (_†Merycodus osborni_, middle Miocene, and _†M. furcatus_, upper Miocene). Restored from specimens in the American Museum.]