[Illustration:  Fig. 265.—­Skull of the Urns (Bos primigenius).  Post-Pliocene and Recent. (After Owen.)]

In addition to the above, the Post-Pliocene deposits of Europe and North America have yielded the remains of various Sheep and Oxen.  One of the most interesting of the latter is the “Urus” or Wild Bull (Bos primigenius, fig. 265), which, though much larger than any of the existing fossils, is believed to be specifically undistinguishable from the domestic Ox (Bos taurus), and to be possibly the ancestor of some of the larger European varieties of oxen.  In the earlier part of its existence the Urus ranged over Europe and Britain in company with the Woolly Rhinoceros and the Mammoth; but it long survived these, and does not appear to have been finally exterminated till about the twelfth century.  Another remarkable member of the Post-Pliocene Cattle, also to begin with an associate of the Mammoth and Rhinoceros, is the European Bison or “Aurochs” (Bison priscus).  This “maned” ox formerly abounded in Europe in Post-Glacial times, and was not rare even in the later periods of the Roman empire, though much diminished in numbers, and driven back into the wilder and more inaccessible parts of the country.  At present this fine species has been so nearly exterminated that it no longer exists in Europe save in Lithuania, where its preservation has been secured by rigid protective laws.  Lastly, the Post-Pliocene deposits have yielded the remains of the singular living animal which is known as the Musk-ox or Musk-sheep (Ovibos moschatus).  At the present day, the Musk-ox is an inhabitant of the “barren grounds” of Arctic America, and it is remarkable for the great length of its hair.  It is, like the Reindeer, a distinctively northern animal; but it enjoyed during the Glacial period a much wider range than it has at the present day, the conditions suitable for its existence being then extended over a considerable portion of the northern hemisphere.  Thus remains of the Musk-Ox are found in greater or less abundance in Post-Pliocene deposits over a great part of Europe, extending even to the south of France; and closely-related forms are found in similar deposits in the United States.

[Illustration:  Fig. 266.—­Skeleton of the Mammoth (Elephas primigenius).  Portions of the integument still adhere to the head, and the thick skin of the soles is still attached to the feet.  Post-Pliocene.]

Coming to the Proboscideans, we find that the Mastodons seem to have disappeared in Europe at the close of the Pliocene period, or at the very commencement of the Post-Pliocene.  In the New World, on the other hand, a species of Mastodon (M.  Americanus or M.  Ohioticus) is found abundantly in deposits of Post-Pliocene age, from Canada to Texas.  Very perfect skeletons of this species have been exhumed from morasses and swamps, and large individuals attained a length (exclusive