The bison is a shaggy, brown animal, about the size of the well-known Durham breed of cattle, but with a larger head and a prominent hump on the shoulders (Fig. 31). The hind quarters are small in comparison with the massive head and shoulders, and appear weak. The head, neck, shoulders, and fore legs are covered with thick matted hair, at times 16 inches long and of a dark-brown colour merging into black. The straight black hair beneath the chin of the bull is usually some 10 inches in length, and as the animal carries its head low, frequently sweeps the ground. Back of the medial portion of the body the hair is short and of a yellowish-brown colour, or "between dark umber and a living-liver brown," as Audubon says. There is much variation in colour, however, and distinct varieties have been stated to exist. The horns, hoofs, and a bare space about the nostrils and mouth are black. The weight of a fully grown bull is about 2,000 pounds, and of a cow 1,200 pounds. [Illustration: FIG. 32.--Range of the Bison.] The boundaries of the region in which the bison has been seen by white men, together with the dates of its extermination in various sections of the country, etc., are shown in Fig. 32. In about 1870 the vast herd which ranged over the treeless plateaus and Prairie plains between the Rio Grande and Great Slave Lake was divided, owing to the great slaughter that occurred in the vicinity of the Central Pacific Railroad, into two herds, one of which had its summer range in Montana and neighbouring territory, but moved northward in summer into Canada, while the other fed on the plains of the west Texas region in winter and moved northward in summer as far as southern Nebraska. In each case a southward movement was begun as winter approached, but these seasonal changes scarcely warrant the name of migrations.