423 
Geology of the Environs of Petersburg. 
and those of Shoulcova, which are but a prolongation of them to the 
eastward, partake of the same nature. 
Where the upper beds of the subjacent stratum are sandy, the 
limestone is also sandy to a great degree. 
Hippurites and fungites, of small size, are not rare ; in a few 
places they are mixed with small corallines and terebratulites, and 
joints of encrini in a confused mass. This resembles much some 
other limestones of the interior of Russia. 
The strata of the limestone are seldom above half a foot in 
thickness, and although, where tolerably solid, it is raised in blocks 
of a foot and a half, yet the lines of junction are always easily to be 
traced. Their general position throughout the country varies but 
little from the horizontal, except in a few cases, which will be here- 
after specified. 
In the cabinet of the Mineralogical Society at Petersburg, are two 
small specimens of galena enclosed in a mass of pyrites, said to have 
been found in the limestone : place unknown. Pyrites itself occurs 
but rarely in this stratum. 
Copper was formerly dug for at Doudorof : I could never find the 
precise spot, but suppose it to have been near some pits at the east 
foot of the hill not far from Varexila. A specimen of the green 
carbonate is in the cabinet before mentioned. 
n n 
This limestone is called Pleta by the Russians, and Paas by the 
Fins. Its principal mass occupies the great plateau or table land of 
the central part of Ingria, as described in the beginning of this 
memoir : its outcrop running just within that of the intermediate 
bed, which may be traced all round it, except where covered by 
gravel or bogs. It is remarkable, that those denudations which 
penetrate farthest within the outlier of this mass, shew the sub- 
jacent intermediate bed in its thinnest st^ite, while round the 
Vol. V. 3 II 
