108 . REPORT—1840. 
has also a mineral resemblance to chalk, in being loaded with thin 
bands of flints, sometimes concretionary, in which corals occur. As- 
sociated 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 appearance of white limestone. With these grand 
gypseous deposits, in which are occasionally large concretions, alternate 
two or three thin bands of limestone, in one of which the authors de- 
tected fossil shells (Avicuéa) which are new to them. This and other 
peculiar bands near Ust-Vaga, which are rather higher in the series, 
will be described hereafter, when the fossil shells have been examined. 
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 very same large Productus hemisphericus, so well known in 
the isle of Arran, and other parts of England and Scotland; and the 
white beds being loaded (among some new forms described by Fischer) 
with many of the species published by Phillips and by Sowerby, as well 
as by several characteristic corals ( Chetites radians, &c.). 
Owing to its mineral aspect, this rock has also, till within the last 
year, been much misunderstood; but Colonel Helmersen having ob- 
served its position in the Waldai Hills and its association with the 
coal, and having ascertained the nature of the fossils from M. Von 
Buch, he first gave out that, in that district, it must be considered the 
true mountain limestone. The authors have completely confirmed this 
view, by ascending and descending sections, and have very largely 
extended it. 
4. Newer Red Formations.—The extent to which the authors are 
inclined to believe in the existence of newer red deposits, and their 
explanation of what they believed to be a vast basin in the govern- 
ments of Vologda, Nijnii, Kostroma, &c., was reserved for a future 
occasion. 
5. Oolitic or Jurassie Series —When the authors visited Russia, it 
was still a great problem whether there was, or was not, a series of strata 
to connect the lower carboniferous strata above described with cer- 
tain rocks of the oolitie series, which have been long known to exist 
in the south of Russia, and some of the fossils of which were sent 
to England by Mr. Strangways. 
Some of these beds, which rest at once on the great red formation along 
the banks of the Volga, between Kostroma and Nijnii Novogorod, be- 
long unquestionably to the middle oolite, as they contain Ammonites and 
Belemnites identical in species with those of the Oxford clay and “ Kel- 
loway Rock” of Smith. Other shells found near Jelatma and Kaccimof 
and Moscow had been collected; but on this point Mr. Murchison 
reserved his opinion till the examination and comparison of the organic 
remains had taken place in London. 
At Moscow, Jelatma and Kaccimof, however, there is no ambiguity, 
for there these shales of the oolitic system, some of the fossils of 
which resemble those of the lias, rest at once on the white carbonife- 
