62 
SECTION OF THE DON — ABUNDANCE OF FOSSILS. 
from zoological evidences ; for the prevalent forms are identical with those of the 
lowest Devonian rocks of other countries L These beds may be strictly com- 
pared with the Devonian limestones of the Boulonnais, there being at least twelve 
species of characteristic shells common to the Russian and French localities, as 
will be detailed in the sequel. On the whole, we may say, that the sections of 
the Upper Don 2 have afforded about thirty species of true Devonian fossils, 
i. e. of characters intermediate between those of the Silurian and carboniferous 
types. 
Our last survey of Russia has, indeed, impressed us forcibly with the value of 
possessing a correct knowledge of the fossils of this system. Unacquainted 
with them, and the place which they occupy in the series, the best field-geolo- 
gist might have been misled in making out the true succession, in the little- 
disturbed and undulating region of Central Russia ; for in proceeding from the 
Valdai Hills on the north he quits a Devonian zone, with a true “ Old Red ” 
type, dipping under the Carboniferous rocks of Moscow, and having passed 
through the latter, he finds himself suddenly in a yellow-coloured region, entirely 
dissimilar in structure to what he has seen in any of the northern governments. 
Hence he might naturally conclude — the order of superposition being difficult to 
trace, and the level of the country being considerably higher than that of Moscow 
— that he had reached a horizon superior to the carboniferous limestone, and which, 
from its aspect, might be the Zeclistein or magnesian limestone : and yet this very 
zone is the true equivalent of the Old Red system, which, loaded with its cha- 
racteristic fossils, rises out in a dome or broad-backed elevation to form the central 
watersheds of the empire. 
General view of the Organic Remains of the Devonian Rocks of Russia . — Having 
shown that the widely spread deposits (No. 3 of the Map, and coloured dull red) 
are the true equivalents of the Devonian rocks of Western Europe, their founda- 
tion being based upon Silurian strata and their upper beds covered by carboniferous 
formations, we now offer a few general remarks upon their organic remains. The 
reader who is acquainted with the characteristic fossils of this age in Scotland, 
England, and parts of Germany and France, has learnt by the perusal of the pre- 
ceding pages, that in its Russian development, the system contains an union of 
1 See Murchison on the Devonian strata of the Boulonnais, Bulletin de la Societe Geol. de France, 
vol. xi. p. 229. 
4 See description of the Organic Remains in the Third Part. 
