Carboniferous deposits occur over nearly the whole of E. Russia, their W. boundary being a line drawn from Archangel to the upper Dnieper, thence to the upper Don, and S. to the mouth of the last-named river, with a long narrow gulf extending W. to encircle the plateau of the Donets. They are visible, however, only on the W. borders of this region, being covered towards the E. by thick Permian and Triassic strata. Russia has three large coal-bearing regions—the Moscow basin, the Donets region and the Urals. In the Valdai plateau there are only a few beds of mediocre coal. In the Moscow basin, which was a broad gulf of the Carboniferous sea, coal appears as isolated inconstant seams amidst littoral deposits, the formation of which was favoured by frequent minor subsidences of the seacoast. The coal is here confined to the lower division of the system; the Upper Carboniferous (corresponding with the English Coal-Measures) is exclusively marine, consisting chiefly of Fusulina limestone. The Donets Coal-Measures, containing abundant remains of a rich land-flora, cover nearly i6,000 sq. m., and comprise a valuable stock of excellent anthracite and coal, together with iron-mines. In this basin, as in W. Europe generally, the principal coal seams occur in the Upper Carboniferous, while the Lower Carboniferous is mainly composed of marine deposits, with, however, the first bed of coal near its summit. Several smaller coalfields on the slopes of the Urals and on the Timan ridge may be added to the above. The Polish coalfields belong to another Carboniferous area of deposit, which extended over Silesia. The Permian limestones and marls occupy a strip in E. Russia of much less extent than that assigned to them by Murchison. The variegated marls of E. Russia, rich in salt-springs, but very poor in fossils, are now held by most Russian geologists to be Triassic. The Permian deposits contain marine shells and also remains of plants similar to those of England and Germany. But in the government of Vologda, on the rivers Sukhona and N. Dvina, Glossopteris, Noeggerathiopsis and other ferns characteristic of the Indian Gondwana beds have been found; and with these are numerous remains of reptiles similar to those which occur in the Indian deposits. In the Urals the marine fades is more fully developed and the fauna shows affinities with that of the Productus limestone of the Central Asian mountain belt. During the Jurassic period the sea began again to invade Russia from S.E. and N.W. The limits of the Russian Jurassic system may be represented by a line drawn from the double valley of the Sukhona and Vytchegda to that of the upper Volga, and thence to Kieff, with a wide gulf penetrating towards the N.W. Within this space three depressions, all running S.W. to N.E., are filled up with Upper Jurassic deposits. They are much denuded in the higher parts of this region, and appear but as isolated islands in central Russia.