162 
SECTIONS OF THE VOLGA AND SVIAGA. 
white marls and marlstone, approaching to a chalky consistence. In following the 
course of the Kama from Tchistopol towards its mouth, a considerable change, 
however, takes place in the structure of the country. The beds of grit with plants 
disappear, large masses of gypsum succeed, and at Shuran the cliff on the right 
bank of the stream, about eighty feet high, consists in the lowest part of yellowish 
cream-coloured and spotted marly limestone with small spinose Producti ( Pro - 
ductus Cancrini). The central portion is made up of limestone as white as chalk, 
of conch oidal fracture, with Modiolse, and thin courses of gypsum covered by a 
sub-brecciated, small concretionary, marly limestone. The upper part contains 
white, greenish and reddish marls and marlstone, with a few thin plates of yellowish 
and greenish grit ; upon this lies the ordinary reddish-coloured argillaceous detri- 
tus, which covers large parts of this district, where it is not occupied by the black 
earth or Tchornozem. 
Near the village of Cliutziski on the Volga, below Kazan, the limestone is seen 
to rise in horizontal beds from the level of the river to a height of fifty or sixty 
feet, and in it we observed many fossils. Among them are Producius Cancrini, 
Avicula antiqua (Munster), Modiolcc and a small bivalve like a Corbula. Gypsum 
does not show itself in this locality, but is found in abundance lower down the 
stream, and also higher up at Verkni Uslon. The fossiliferous limestone here, as 
in all other parts of this neighbourhood, is surmounted towards the west, where 
the country rises, by red and white and green marls, with courses of marly tufa- 
ceous limestone, which beds are void of organic remains. 
The finest, however, of all the examples of the limestone and its passage upwards 
into the overlying deposits, is offered in the cliffs exposed in the promontory 
which forms the right bank of the Volga at Verkni Uslon, and extends to Sviaga 
near Sviask. This woodcut exhibits, in fact, a transverse section from Kazan 1 to 
1 Borings and sinkings to a considerable extent had been carried on before our arrival at Kazan, in the 
hope of obtaining a purer water than that now in use, and these works passed through various beds of 
limestone, argillaceous marl, sand, &c. This was one of the many improvements which were pursued 
