Even more typically northern than the Caribou were the Musk-Oxen, of which two genera occurred in the late Pleistocene. One of these, _†Symbos_, is extinct and was characterized by its short horns; the other, _Ovibos_, is the genus to which the existing species, _O. moschatus_ and _O. wardi_, belong and is now confined to the extreme north of the continent, the Arctic islands and Greenland. The remains of Musk-Oxen have been found mostly along the great terminal moraine which marks the front of the last ice-invasion, but they occurred also as far south as Oklahoma, and in Utah they ranged far to the south of the ice-front. Nothing could be more conclusive evidence of a climate much colder than the modern one than the presence of Caribou and Musk-Oxen in the United States and of the Walrus on the coast of Georgia. The smaller animals were much as they are now, differing only in range. The †sabre-tooth tigers, the last of a most interesting line, persisted in the south, and an extinct genus of skunks has been discovered in Arkansas, but otherwise the Carnivora were entirely modern in character. Unfortunately, these smaller animals are very incompletely known, much the richest aggregation which has yet been found being that collected by Mr. Brown in the Conard Fissure, Arkansas. From this collection Mr. Brown has described thirty-seven genera and fifty-one species of mammals, of which four genera and twenty-four species are extinct. That is to say, less than one-ninth of the genera and one-half of the species represent extinct forms. Contrast this with the middle Pleistocene assemblage found in the Port Kennedy cavern in eastern Pennsylvania, of sixty-four species with at least forty extinct ones. The foregoing sketch, brief and imperfect as it necessarily is, makes it sufficiently plain that North America during the Pleistocene was far richer in mammalian life than it was when the continent was first settled by Europeans. When we make the proper allowance for the many forms which undoubtedly remain to be discovered and for those which may have vanished without leaving a trace behind them, the contrast becomes all the more striking. Not only did Pleistocene North America have substantially all the mammals that it now possesses, but it had many more. The lions and †sabre-tooth tigers, the gigantic †short-faced bears, the tapirs and many varieties of horses, large and small, the camels and llamas, many species of bisons, some of enormous proportions, several forms allied to the Musk-Ox, the elephants and †mastodons, the †giant beavers and South American water-hogs, the huge †ground-sloths and †glyptodonts, have all disappeared, leaving a continent, that, by contrast, is “zoölogically impoverished.” The Pleistocene fauna was strangely mixed in character, the free roads of migration bringing together Old World and South American types, and mingling them with indigenous forms in a cosmopolitan assemblage.