Second Geological Survey of Russia in Europe. 61 



loaded with Ichthyolites and Mollusks, all eminently characteristic 

 of the Devonian system*. This mass sinks to the north under a 

 great band of carboniferous rocks (Tula, Kaluga, &c.), the northern 

 part of which was last year described as occupying the territory 

 around Moscow and extending thence north-eastwards to the neigh- 

 bourhood of Archangel : to the south it is lost under younger accu- 

 mulations of secondary age. The dome of palaeozoic rocks rising 

 to an altitude of about 800 feet above the sea, was thus found to 

 divide Russia into two distinct geological basins, viz. that of the 

 carboniferous limestone of Moscow on the north, and that of the 

 Jurassic, cretaceous and tertiary deposits on the south. One of the 

 most remarkable features of this central mass consists in the litho- 

 logical character of its rocks, as contrasted with that of formations 

 of the same age, and containing the same fossils, in the northern 

 governments ; for whilst the latter in their range from the western 

 borders of Lithuania to Olonetz and Archangel, including part of the 

 Walda'i Hills (see last year's memoir, Phil.Mag.S.3.vol.xix.p.492), 

 are invariably made up of sands, sandstones, marls, and impure lime- 

 stones, of prevailing red and green colours ; their equivalents in Orel 

 and Voroneje are yellow and white marlstones and limestones, the latter 

 often in the state of magnesian limestone, and resembling in external 

 aspect the Zechstein of Germany or the rocks of Sunderland in the . 

 British Isles. In addition to the characteristic fossils, enumerated 

 last year from the great northern Devonian region, the central 

 masses, particularly at Voroneje, have afforded many shells which 

 have been published as typical of strata of the same age in West- 

 ern Europe, such as Spirifer Archiaci, S. Verneuillii, Leptama Dn- 

 tertrii, Productus productoides, of the Boulonnais f, together with 

 Orthis crenistria, Productus spinulosus, and Aulopora, Favosites, and 

 other polypifers. It is indeed very remarkable, that in countries so 

 distant from each other as the central region of Russia and the 

 Boulonnais, twelve species at least of the fossils found at Voroneje 

 should prove to be common to the rocks of the same age in both 

 localities, and that in both instances the order of superposition 

 should be so clear. The superior value, however, of the Russian 

 sections of this division of the Palaeozoic rocks over those in every 

 other part of Europe, consists in the conjunction before adverted 

 to and so generally observed in Russia, of Holoptychius and other 

 fishes of the old red sandstone of Scotland and England, with the 



* A part of the tract between Orel and Lichwin was examined by Colonel 

 Helmersen during the same summer, and before the visit of the authors, 

 and he also recognised the existence of Devonian rocks. The authors, 

 however, were quite unaware of this circumstance when they first published 

 their views on this point at the end of September 1841, in a letter addressed 

 to Dr. Fischer de Waldheim, and it was on their arrival at St. Petersburgh 

 only, that they found that Colonel Helmersen had come to the same con- 

 clusions as themselves, in respect to a portion of the country in question. — 

 See Bulletin de la Society Imperiale des Naturalistes de Moscou, Oct. 1841. 



f See Mr. Murchison on the Boulonnais. — Bulletin de la Societe Geol. 

 de France, tome xi. 



