402 
many other places, is seen to overlie the old red sandstone,’ The © 
inferior beds consist of incoherent sandstones and bituminous shale; 
which sometimes contain thin beds of impure pyritous coal, and im- 
pressions of several plants well known in the carboniferous system 
of our own islands. ‘These are surmounted by various bands of 
limestone, the lowest of which only have occasionally some minera- 
logical resemblance to the mountain limestone of Western Europe ; 
other beds being lithologically undistinguishable from the magne- 
sian limestone of England; some from a pisolite; a third and very 
prevalent band of considerable thickness is milk-white, and not more 
compact than the caleaire grossier of Paris.- This white Productus 
limestone was traced by the authors from the neighbourhood of 
Moscow to beyond Archangel (and they ascertained that it ranged 
far into the country of the Samoiedes), a distance of not less than 
1000 miles. This formation has also a mineral resemblance to chalk, 
in being loaded with thin bands of flints, sometimes concretionary, 
in which shells and corals occur. Associated with this formation, 
on the banks of the Dwina, about 200 wersts above Archangel, and 
south of Siisskaia, are splendid bedded masses of white gypsum, 
which, for many miles, present at a little distance all the appear- 
ance of white limestone*. With these grand gypseous deposits, in 
which are occasionally large concretions, two or three thin bands of 
limestone alternate, in one of which the authors detected fossil shells 
(Avicula) which are new to them. Other peculiar bands near Ust- 
Vaga, which are rather higher in the series, contain a Productus 
approaching to P. scabriculus, with Pectens and Corals. 
The carboniferous limestone of Russia is highly fossiliferous, and 
from the normal and unaltered condition of most of the beds, the 
fossils are generally in an excellent state of preservation. Among 
them are many well-known British species, the lower beds being 
distinguished by the large Productus hemisphericus so well known 
in' the same lower beds of England and Scotland; and the white 
beds being loaded with many of the species published by Fischer, 
Phillips and Sowerby, such as Productus Martini, P. punctatus, San- 
guinolaria sulcata, Spirifer Mosquensis, Cardium aleforme, Cidaris 
vetustus, together with the abundant and characteristic Russian coral, 
Chetites radians (found, according to Mr. Lonsdale, in the carbo- 
niferous limestone of Bristol, &c.), and the Lithostrition floriformis, 
one of the most characteristic fossils of the English carboniferous 
limestone, &c. 
Owing to its mineral aspect, the age of this rock. had, till within 
the last year, been misunderstood; but Colonel Helmersen having 
observed its position in the Waldai Hills and its association with 
certain beds of coal, and having ascertained the nature of the fossils 
through the examination of M. von Buch, he first gave out in Rus- 
sia, that it must be considered the true mountain limestone.” The 
authors have completely confirmed this view, by ascending and de- 
scending sections, and have largely extended it. 
* See M. Roberts’s account of these white cliffs, which he supposed to 
be limestone.— Bulletin de la Soc. Géol. de France, 1840: 
