In the New World pouched rats (Geomyidae) the pouches open externally on the cheeks.
Schistocolor), the beaver, variable hare, wild boar, roebuck, stag, reindeer, elk and Phoca annelata of Lake Baikal - all these are common alike to Europe and to Siberia; while the bear, musk-deer (Moschus moschi- f erus), ermine, sable, pouched marmot or souslik (Spermophilus eversmani), Arvicola obscures and Lagomys hyperboraeus, distributed over Siberia, may be considered as belonging to the arctic fauna.
In hares and pacas the inside of the cheeks is hairy; and in some species, pouched rats and hamsters, there are large internal cheek-pouches lined with hair, which open near the angles of the mouth and extend backwards behind the ears.
The first class includes the isabelline bear, badger, pole-cat, ermine, roe and fallow deer, wild ass, Syrian squirrel, pouched marmoset, gerbill and leopard.
The American pouched rats, or pocket-gophers, constitute the third section, Geomyoidea, with the single family Geomyidae.
The various species of rapacious animals are disappearing, together with the colonies of marmots; the insectivores are also becoming scarce in consequence of the destruction of insects; while vermin, such as the suslik, or pouched marmot (Spermophilus), and the destructive insects which are a scourge to agriculture, become a real plague.