Mississippi Valley nearly or quite to the Gulf of Mexico. In California was _E. †occidentalis_, equalling _E. †complicatus_ in size, but with much more simple teeth, and associated with it the much larger _E. †pacificus_, which was inferior only to _E. †giganteus_ and therefore the second largest of the American Pleistocene horses. To one who knows nothing of the geological history of North America it would be natural to suppose that the Pleistocene horses must have been immigrants from the Old World, which failed to establish themselves permanently here, since they completely disappeared before the discovery of the continent by Europeans. This would, however, be a mistaken inference, for North America was for long ages the chief area of development of the equine family, which may here be traced in almost unbroken continuity from the lower Eocene to the Pliocene. On the other hand, it is quite possible that some of the species were immigrants. Tapirs, which are now confined to southern Asia, Central and South America, were not uncommon in the forested parts of eastern North America as far north as Pennsylvania, but they have not been found west of the Mississippi in the plains region. Two species are known, a larger and heavier one, _Tapirus †haysii_, and a smaller one which seems to be identical with the living _T. terrestris_ of Central and South America. Like the horses, the tapirs had a long history of development in North America and may well have originated here, but they withdrew from the continent in the Pleistocene, probably yielding to the last of the glacial advances. There was likewise a much greater variety of Artiodactyla than North America can boast at the present day; some were autochthonous, but, for the most part, they were migrants from the eastern hemisphere, where the great group of the true ruminants (Pecora) passed through the greater part of its development and where its headquarters still are. Indigenous were the peccaries, or American swine, which still occur from Texas south to Brazil. In Pleistocene time they ranged over nearly all of the United States, as far northward as Pennsylvania, and across the plains to the Pacific coast; they were represented by two genera, now extinct, one of which (_†Platygonus_) had crested grinding teeth and much longer legs than the modern peccaries. Another indigenous group, strange as that may seem, is the suborder (Tylopoda) of the camels and llamas, both of which are represented in the North American Pleistocene, the descendants of a very long American ancestry. Some of these tylopodans were far larger than existing forms, and at least one species extended its range to Alaska.