This group of Flying Squirrels is also represented on the North American continent. The number of species seems rather uncertain, some authors making it two, others four; while Mr. J. A. Allen regards all the North American Flying Squirrels as belonging to a single species, which varies greatly in size in different localities. This species is the ASSAPAN (_Sciuropterus volucella_), one of the smallest of its family, the length of its head and body being only from four and three-quarters to seven and a half inches; the smaller specimens (var. _volucella_) being found in the more southern States, and even as far south as Guatemala; and the larger ones (var. _hudsonius_) in more northern localities. In its habits this elegant little Squirrel resembles the Polatouche, but appears to be more sociable. It thrives well in confinement. Besides these Tree Squirrels, a few species of the Sciurine sub-family live upon the ground. In Abyssinia and in other parts of Africa some curious animals, forming the genus _Xerus_, are found, distinguished by their very small ears, longish limbs, and the singular texture of their hair, which scantily clothes the skin and generally takes the form of flattened spines. They have a slender body, a pointed head, and a longish tail. These animals live in elevated forest regions, and even upon comparatively barren steppes, where they burrow in the ground under rocks, or among the roots of trees and bushes. They are diurnal, and feed chiefly upon buds and herbage, but also devour small birds, eggs, and insects. The best known species (_Xerus rutilans_) is about twenty inches long, of which the tail makes about nine inches. Its colour is reddish-yellow above, becoming paler on the sides, and whitish below. [Illustration: COMMON CHIPMUNK.]