The carefully kept statistics of the Bielowitza herd in Grodno, western Russia, which includes nearly all but the few wild ones, shows that between 1833 and 1857 they increased in number from 768 to 1,898, but from this maximum the decrease has been constant, with trifling halts, until in 1892 less than five hundred were left; so that even if the Peace River bison are counted with the remnant of the American species, it is probable that the survivors of each race are about equal in number. It is true that the number of our own species has lately been placed as high as a thousand, but even if these figures are correct, the seeds of decay from internal causes, such as inbreeding and the degeneration of restraint, are already sown, and the inevitable end of the race is not far off. The Peace River, or woodland, bison has lately been separated as a sub-species _(B. bison athabascae)_, distinguished from the southern and better known form by superior size, a wider forehead, longer, more slender and incurved horns, and by a thicker and softer coat, which is also darker in color. Now, it is an interesting fact that a fossil bison skull from the lower Pliocene of India resembles the present European species, and in later geological times very similar bisons closely allied to each other, if not identical, inhabited all northern regions, including America. These were large animals with wide skulls, and there is little doubt that from this circumpolar form came both of the bisons now inhabiting Europe and America. Out of some half dozen fossil bison which have been described from America, none earlier than the latest Tertiary, _Bison latifrons_ from the Pleistocene seems likely to have been the immediate ancestor of recent American species, and as the one skull of the woodland bison which has been examined resembles both _latifrons_ and the European species more than the plains species does, it seems probable that these two more nearly represent the primitive bison, of which the former inhabitant of the prairies is a more modified descendant. The process of elimination has at last led to this outline definition of a bison, but among the ungulates we have passed over, there are certain others which concern us because they are American.