130 
CARBONIFEROUS LIMESTONE NEAR STERLITAMAK. 
band before alluded to) occupies cliffs 400 feet in height, and is filled with Spirifer 
Mosquensis, Productus antiquatus, and P. concinnus. 
Carboniferous Limestone near Sterlitamak. — The inner and outer zones of carboni- 
ferous limestone which we have sketched, are probably confluent a little to the 
south of Ust Simsk. Our survey, however, of the western flanks of the Ural was 
not sufficiently detailed, to enable us to ascertain this point precisely, nor yet to 
trace a continuous zone of Goniatite grits and flags, to the west of the outer band of 
limestone. In emerging from the Ural, by a traverse from Ufinsk to Ufa, we found 
ourselves suddenly in a low, obscure tract occupied by red deposits. In quitting 
the chain, however, by another parallel traverse from Verch-Uralsk to Sterlitamak, 
the same carboniferous limestone is again seen to range upon two lines from north to 
south, inclosing between them a small trough of Permian deposits, composed of 
gypsum, limestone, red marl, &c. The innermost of these bands forms the boundary 
of the mountainous region, being a calcareous fringe which hangs upon the red 
conglomerates and older rocks of Devonian and Silurian age. Whatever inver- 
sions and contortions may be seen in the Northern Ural, we here distinctly per- 
ceive the lower beds of the carboniferous limestone, with Productus striatus and 
other fossils, reposing upon a quartzose series of beds of reddish colour, spotted 
with green, and in many parts much resembling the Old Red Sandstone of Scot- 
land ; like which it contains pebbles, and is in parts a conglomerate. These rela- 
tions are seen on the western flanks of Akritau, as is expressed in the coloured 
transverse section from the Ural to the west (PL IE fig. 1 .). In their range to the 
east, or among the mountains, these calcareous beds are subject to many dislo- 
cations, but where they terminate by a great fault against the low country watered 
by the rivulet Ziganofka, they are in almost horizontal positions. In these cliffs 
the limestone is both of light grey and black colours, with white veins, is often 
flaglike and fissile, with numerous thin courses of black flint, and contains the 
Spirifer Mosquensis and many carboniferous fossils. 
The outer zone of limestone which rises from beneath the trough of Permian 
rocks, running nearly from north to south, and close along the left bank of 
the river Bielaya, is marked by four subconical hills, which appear like volcanic 
elevations in the flat district, in which they are protruded to the surface. The hill 
of Tchekatau, immediately to the east of Sterlitamak and the third of the peaks 
counting from the north, may be described as a good example of the ridge. It 
is a rugged, bare rock of some height, with a double top, which rising abruptly 
