254 
EUROPEAN EQUIVALENTS OF THESE JURASSIC ROCKS. 
white limestone of Cracow in Poland, and is, we conceive, of the exact age of the 
coral rag and calcareous grit of England. 
Detailed examination of the fossils derived from the lowest and largei forma- 
tion has convinced M. D’Orbigny, that they belong to two stratigraphical 
divisions first established by William Smith, viz. the Kelloway rock and Oxfoid 
clay ; and judging from the remains we laid before him, he thinks it possible to 
distinguish, with as much precision as in France or England, the lowest Oxfordian 
or Kelloway rock, from the overlying beds of the Oxford clay. Thus, according 
to M. D’Orbigny, the fossils from Moscow, Jelatma on the Oka, the North Ural 
and the tracts near Simbirsk and in the government of Orenburg, contain similar 
assemblages of forms, which he classes with the remains of the Kelloway rock of 
England or the lower stage of his “ Terrain Oxfordien”; the Ammonites Gulielmi 
(Sow.) and the A. Fournetianus (D’Orb.) being the characteristic fossils. On the 
other hand, M. D’Orbigny believes, that the beds at Makarief on the Unja, near 
Pies on the Volga, and at Saratof, represent the middle beds of the “ Terrain Ox- 
fordien,” or simply the Oxford clay of England ; of these the Ammonites cordatus is 
characteristic ‘. 
Adopting invariably those views of classification, which agree with the dis- 
tribution of organic life, we have never, we trust, undervalued the importance 
of clear evidences of superposition. Now, in Russia the facts (as we have related 
them) are, that the Jurassic beds which are in contact with inferior rocks, are those 
near Pies, Makarief and Moscow. Unquestionably, therefore, in a country void 
of all great dislocations and with little variation in the level and inclination of the 
strata, such beds may naturally be supposed to lie low in the Jurassic series. 
Judging from the few fossils we could collect in the vicinity of those junctions, 
M. D’Orbigny is led to believe, that two of these masses belong to his middle 
stage of the “ Terrain Oxfordien,” whilst a third (that of Moscow) is on the par- 
allel of his lower stage. In relation, however, to the sections on the Volga near 
Pies, it must be stated, that in the Jurassic shale in contact with the red Per- 
mian rocks, we obtained Belemnites only ; whilst the other fossils were gathered 
from mouldering slopes and at intervals along the river banks, where no such 
junctions are visible. Among these fossils, the Gryphcea dilatata, as already said, 
was not unfrequent, and it was associated with Ammonites cordatus, Turbo mu- 
rrains, &c. Again, in the Jura beds upon the Oka (near Jelatma), referred by 
1 In England this fossil is usually found in the “ calcareous grit. 
