Of these the black-earth region - about 150,000,000 acres - which reaches from the Carpathians to the Urals, from the Pinsk marshes in the S.W.
In the extensive region covered with boulder-clay the black earth appears only in isolated places, and the soil consists for the most part of a sandy clay, containing a much smaller admixture of humus.
For days together the traveller sees no other vegetation; even this, however, disappears as he approaches the regions recently left dry by the Caspian, where saline clays, bearing a few Salsolaceae, or mere sand, take the place of the black earth.
European plains - the tundras, including the Arctic islands, the forest region, especially the coniferous part of it, and the ante-steppe and steppes of the black earth region.
Bogdanov, Birds and Mammals of the Black-Earth Region of the Volga Basin (in Russian, Kazan, 1871); Karelin for the southern Urals; Kessler for fishes; Strauch, Die Schlangen des Russ.
