In the ante-steppe the forest species proper, such as Pteromys volans and Tamias striatus, disappear, but common squirrel (Sciurus vulgaris), weasel and bear are still met with in the forests.
The genus which is common to the northern parts of both hemispheres is distinguished by the large cheek-pouches and by the absence or rudimentary condition of the claw of the first hind-toe, resembles Tamias in the slender form of the body, but displays great variation in the length of the tail, which may be a mere stump, or comparatively long.
With Tamias (sometimes split into Tamias and Eutamias) we reach the North American striped groundsquirrels, or chipmunks, well characterized by the large internal cheek-pouches, with one outlying species in Northern Asia and Europe (see GROUND-Squirrel).