The buffaloes (Bubalus) are large and clumsy animals with horns more or less compressed or flattened at their bases, set low down on the vertex, which does not show the high transverse ridge of true oxen and gaurs.  In old bulls of the African species the horns meet at their base and completely cover the forehead.  In the arni of India they are enormously long.  The dorsal spines are not much elongated, and there is no distinct hump; the premaxillae are long enough to reach the nasals.  Hair is scanty all over the body, and old animals are almost wholly bare.  The small and interesting anoa of Celebes, and the tamarao of Mindoro, are nearly related in all important respects to the Indian buffalo, and the carabao, used for draught and burden in the Philippines, belongs to a long domesticated race of the same animal.

Finally, in the genus Bison the horns are below the vertex as in buffaloes, but are set far apart at the base, which is cylindrical; they are short and their curve is forward, upward and inward; the anterior dorsal and the last cervical vertebrae have long spines which bear a distinct hump on the shoulders; the premaxillae are short and never reach the nasals; there are fourteen, or occasionally fifteen, pairs of ribs, all other oxen having but thirteen, and there is a heavy mane about the neck and shoulders.  The yak of central Asia is very bison-like in some respects, but in others departs in the direction of oxen.

So at last, group by group, we have gone through the ungulates, and the bisons alone are left, and as the American animal has short, incurved horns, set low down on the skull and far apart at the base; premaxillaries falling short of the nasals; the last cervical and the anterior dorsal vertebrae with spines; fourteen pairs of ribs, and a mane covering the shoulders, we conclude that it is a bison, and as the same characteristics with minor variations are shown by the European species, often, but wrongly, called “aurochs,” we say that these two alone of existing Bovidae are bisons, with the yak as a somewhat questionable relative.

In all essential respects the two bisons are very similar, but minute comparison shows that the European species, Bison bonasus, has a wider and flatter forehead, bearing longer and more slender horns, and all the other distinctive features are less pronounced.  In the American species, Bison bison, the pelvis is less elevated, producing the characteristic slope of the hindquarters.  It is a coincidence that the two regions originally inhabited by the bisons are those in which the white races of men have to the greatest extent thrown their restless energies into the struggle for existence, with the result that extinction to nearly the same degree has overtaken these two near cousins among oxen.  A few wild members of the European species still exist in the Caucasus, as a few of the American are left in British America, but elsewhere both exist only under protection.