166 
SECTIONS OF ITSHALKI. 
scarcely cemented together. This analogy is still more striking when we find that 
the fossils are Retepores, Modiolee, and Ostrea , the latter not easily distinguished 
from the species of more modern periods. The loosely aggregated and detached 
shells which are strewed about as if recently abandoned by the sea, impressed 
us, indeed, so much with the idea of recent deposits, that we could not at first 
bring ourselves to reject the hypothesis of a tertiary basin in this central part of 
Russia. A comparison, however, of the beds of Arzamas with those on thePiana, 
soon convinced us that they were both of the same age and associated with the 
same masses of gypsum and red marl ; and a closer examination taught us, that 
the Retepore, which from its colour, isolation and conservation had so fresh an 
appearance, w r as the same species as that found in the Permian system of other 
parts of Russia. Lastly, we observed Producti and Spirifers in the continuation of 
the oyster beds, containing also the same Retepore and equally lying between the 
gypsum and the red marls. 
The interest attached to these highly fossiliferous strata induces us to offer a few 
more words upon the sections of the Piana. 
Itshalki . — Beneath the red and white marls which occupy the summits of the 
hills at this spot, are seen the shelly beds which vary in very short distances, in 
the state of aggregation of the fossils, and it was in one spot only that we disco- 
vered them in the above-mentioned isolated condition. The lower beds appeared 
for the most part to be the more consolidated. The gypsum is not visible here, 
but from the rapid undulations and circular depressions of the surface, which re- 
minded us of similar forms in the gypseous tracts upon the river Ik, in the govern- 
ment of Orenburg (p. 156), and also in tracts where the same rocks will be pre- 
sently shown to abound near Pinega in the north, we had no doubt that the 
gypsum was immediately beneath us. This locality is unquestionably richer in 
well-preserved shells than any we are acquainted with in the whole range of the 
Permian system, and our successors who may be able to devote a few days to the 
collection of its fossils may probably add new and important forms to our lists. 
In the mean time we have discovered two species of Ostrea, one of which entirely 
disengaged from its hinge, leaves no sort of doubt of the genus to which it belongs. 
It is scarcely necessary for us to acquaint geologists that up to the present time 
the Ostracese have never been found below the Muschelkalk. I he appearance 
therefore of this genus, whose species rapidly augment in the ascending order of 
formations, and no one of which has ever been discovered in the carboniferous 
