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Rh are often tipped with a pencil of hairs, but not invariably. The tail is long, as are also the hairs with which it is clothed&#59; and these are more or less arranged so as to diverge on each side, somewhat like the beards of a feather. In two genera, —the Flying-Squirrels of India, and the adjacent islands (Pteromys), and those of North America and Siberia (Sciuropterus),—the skin of the sides is expanded between the fore and hind limbs, so as to confer the power of performing protracted leaps. Most of the species are arboreal in their habits, but one genus, the pretty Ground Squirrels (Tamias), burrow in the ground. The Sciuridæ are spread over the whole world, with the exception of Australia.

In the typical Squirrels the limbs are free, that is, not connected by an expansion of the skin&#59; the molar teeth are tuberculous, the first one in the upper jaw very small&#59; the upper incisors are chisel-shaped, the lower ones pointed and laterally compressed&#59; and the tail is long and bushy, with the feathered arrangement very apparent.

Few persons are unacquainted with our common Squirrel (Sciurus vulgaris, .), either in its wild state, or in captivity. There are, perhaps, none of our native quadrupeds that can compete with it in grace, sprightliness, and agility, in the beauty of its form and hue, or the arch and yet gentle expression of its countenance. The astonishing freedom and rapidity of its motions&#59; the elegant curves into which it throws its long dilated