CRETACEOUS ROCKS OF SIMBIRSK AND THE VOLGA. 
273 
Jurassic rocks on the Lower Volga, we have already informed our readers, that 
they are overlaid by cretaceous deposits. If we had had sufficient time we mig t 
probably have obtained clearer evidences of the exact order of these strata, in the 
governments of Simbirsk and Sarktof than in any other part of Russia ; for in that 
region the right hank of the Volga is composed of plateaux of considerable alti- 
tude, the beds composing which are occasionally well exposed both on the banks 
of that great river and its tributaries, as vrell as in numerous ravines. 
In respect to the cretaceous beds near the city of Simbirsk, we can say that they 
are of considerable thickness, and that we observed in them the following fossils : 
Ter ebr alula octoplicata, identical with that of Meudon near Paris, T. Defranm, T. 
carnea, Ostrea vesicularis, Pecten serratus, P. undulatus, Inoceramus Cuvieri, Belem- 
nites mucronatus, Lenticulites Comptoni (Nils.), and Frondicularia complanata (Defr.). 
M. Jasikoff of Simbirsk, who has made a most interesting collection of the fossils 
of this tract, which we inspected in his absence, states, that the Cretaceous system 
there presents a descending succession of white chalk, gray and chlontic chalk, 
Ill-provided as we are with the means of defining the geographical limits of the 
cretaceous rocks of this tract, we must, in truth, leave all such efforts to be made 
by M. Jasikoff and geologists resident in the country, and in the mean time simply 
speak of phenomena lower down the Volga which fell under our own notice. 
In travelling from Simbirsk along the right bank of the Volga, towards its 
mouth, we found that the white chalk, wrapping round the Jurassic beds, ranged 
and chalk marl'. 
species, 
the upper beds aTe found Terebratula car 
Hoperi, Belemnites mucronatus, Scaphtes 
fishes. Beneath this formation .however, 
Simbirsk and at Shilovka on the river Uren), in i 
consobrinus, a species which M. D’Orbigny places 
part of the lower greensand of English geologists 
tioned in Part III. of this work, but we shall prese 
covered in the environs of Simbirsk. 
jeoiogisia. * 
.hail presently revert to the deposits by which the white chalk is 
The fossils enumerated by M. Jasikoff will be men- 
