255 
EUROPEAN EQUIVALENTS OF THESE JURASSIC ROCKS. 
M. D’Orbigny to the “ etage inferieure,” we find the same Gryphaea, associated 
with different species of Cephalopods, which are common in the Kelloway rock or 
lower stage ; and hence it might be inferred, that the beds containing them must 
also be the lowest Jurassic stratum in Russia. This however is not the case ; for 
the section at Inkino near Jelatma (p. 234) exhibits the same fossiliferons beds 
resting upon a considerable thickness of Belemnite shale; and a similar order of 
superposition is seen at Moscow. Whether, therefore, this shale he in contact 
with the red marl and sand of Pies or the carboniferous limestone of Moscow, or 
whether, as near Jelatma, the subjacent rocks are hidden from view, it is quite 
manifest, that it forms the lowest Jurassic stratum of Central Russia : and it is 
also equally certain, that this lower stratum contains few fossils, and that the she s 
cited as types of the Kelloway rock are found, both at Inkino and at Moscow, in 
central or overlying beds. . 
But these facts are not at variance with our general views of the identification 
of distant deposits ; for all the Jura rocks of Central and Northern Russia put 
together, are not of greater vertical thickness than one formation only of Western 
Europe/ and their fossils belong, as an united group, to the Oxford clay and 
Kelloway rock of England, or “ Terrain Oxfordien ” of France. We cannot, 
it appears to us, push the parallel further, and expect invariably to find in Russia 
an exact equivalent for the little English band of Kelloway rock. We may, in- 
deed, rest satisfied with proving, that certain strata of Northern and Central 
Russia contain species which characterize the Oxford clay and its sub-forma- 
tion in England and France, -that other beds with plants represent the sands o 
the calcareous grit, whilst the white limestone in Southern Russia is the equiva en 
0f WithouTthTknowledge which we possess of the country, a theorist, whilst de- 
fining more precise geographical limits than we can hope to assign o e 1 
feint parts of this greet Jurassic basin, might endeavour to md, cate Its littoral 
and pelagic deposits. But no such separation can be admitted so long as we know, 
that lithologically and zoologically the strata at Jelatma on the Oka, are un i- 
sthiguishable from the very distant rocks of the North Ural and the has.n of 
Petchora on the one hand, and from those of Moscow on the other. 
At the'same time we are quite read, to admit with M. D'Ortngny, Brat the os. 
sils from Makarief, Pies and Sarttof have generally the aspect of the Oxford clay, 
2 L 2 
