720 
that the ascending order of the strata was continuous from the Bal- 
tic provinces on the north to the Black Sea and Sea of Azof on the 
south, with the exception only of the granitic rocks and carboni- 
ferous tracts of the southern steppes. They were undeceived, 
however, by discovering in the heart of Russia (Orel, Voroneje, 
&c.) a great domelike elevation, which is composed of rocks 
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.) thenorthern 
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 palozoic 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 Waldai Hills (see last year's memoir, anté, p.401 ), are invariably 
made of sands, sandstones, marls, and impure limestones, of pre- 
vailing red and green colours ; their equivalents in Orel and Voro- 
neje 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, Leptena Du- 
tertrii, Producius productoides, of the Boulonnais+, 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 
* 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 Société Impériale des Naturalistes de Moscou, Oct. 1841, 
t+ See Mr. Murchison on the Boulonnais.—Bulletin de la Société Géol. 
de France, tome xi. 
