ON THE GEOLOGY OT RUSSIA IN EUROPE. 
203 
the southern basin of the empire, they are composed of yellow 
sandy marls and limestones, which lithologically might be mis- 
taken for the magnesian limestone beds of our northern countries : 
so inapplicable are miueralogical terms as marks of geological 
epochs. 
In the vastness of their undisturbed and nearly horizontal 
extent, these stmta afford us most instructive proofs of the inti- 
mate connection between the stony condition of the rocks and 
the imbedded fossils ; for, when the calcareous matter is present, 
various moUusks are associated with some fishes, whilst in those 
tracts where the limestones disappear and the beds have the 
characters of the Old Red Sandstone of Scotland, fishes only can 
be detected ; thus presenting a remarkable analogy between the 
distribution of this very ancient fauna and that of existing nature ; 
the present great receptacles of fishes being deep sandy bottoms, 
whilst shelly creatures congregate towards the shores where cal- 
careous springs attract them. I have elsewhere alluded to the 
fishes of this deposit when speaking of the researches of Professor 
Agassiz. 
Carboniferous Rocks. — The Carboniferous deposits, which 
succeed, cover an area as broad as that of the Devonian or Old 
Red rocks ; and they are throughout clearly distinguished by a 
decidedly distinct type of animal life, presentmg in some fami- 
lies an extraordinary number of species absolutely undistinguished 
from those of our own country, published in the works of Sowerby 
and Phillips. This system is eminently calcareous, and exhibits 
a vast marine succession, in which the fossils of the Mountain 
Limestone prevail, v,^hilst in no part of the empire is there a 
trace of the overlying deposits, with which we are familiar under 
the term of " coal-measures.^^ Coal, however, does occur at inter- 
vals, both underlying the carboniferious limestone, as in Ber- 
wickshire, and alternating with its central and upper members, 
as in Northumberland, and the carboniferous valleys of our lake 
country, 
2 Y 
