258 
CONCLUSION. 
mean time, we trust, be satisfied that we have proved, in no ambiguous terms, 
the vast range of this Oxford deposit. Our own survey has, indeed, shown, that 
it is one of the most important members of the secondary rocks of Eastern Eu- 
rope ; for whilst in Great Britain it constitutes a small portion only of the oolites, 
not there occupying above a fifth part of the space covered by that series, in 
Russia it spreads over considerable tracts, to the entire exclusion of the Great 
and Inferior Oolite and Lias beneath, as well as of the Kimmeridge clay and Port- 
land rock above it. In a word, the Oxford formation of Russia is the only deposit 
which there exists, between the palaeozoic rocks upon which it reposes, and the 
cretaceous strata by which it is succeeded. 
P.S. As this sheet was passing finally from our hands to the press, we received a letter from our zealous 
friend Mr. Frears of Moscow, which announces, that M. Jasikoff of Simbirsk, to whose observations 
on the Cretaceous and Tertiary rocks of that government we shall presently refer, has discovered in the 
Jurassic strata a few bones of Ichthyosauri. These remains occur in black calcareo-bituminous schists, 
which seem to pass on the one hand into a limestone, and on the other into greenish sands. These beds 
near Simbirsk are, however, of the same age as those of Moscow ; for they contain some of the same 
species of fossils. Among others which will be noticed in Part III. M. Jasikoff cites Gryphcea dilatata, 
Inoceramus dubius, I. lavigalus, with Avicula, Terebratula, Orbicula, six species of Ammonites, two species 
of Belemnites, &c. 
In reference to what has been said of the sands with plants which overlie the fossiliferous shale of the 
Moskwa, p. 240 et seq., it ought to be stated, that the cast of the Lucina which is mentioned as occur- 
ring in these sands and grits, was found in the overlying beds south of M iatchkova, no such shell having 
ever been detected at Tatarova. We see no reason, however, to doubt our conclusions, that all these 
sandstones in the Government of Moscow are of the same age, and belong to the upper part of the Oxford 
formation. Whether the beds at Troitskoi really constitute, as we suspect, the uppermost limits of this 
series in the Government of Moscow, must be decided hereafter. 
