LOWER LIMESTONE OF TULA AND KALUGA. 
79 
at slight cost. It may therefore doubtless be prolitably used in manufactories, 
and subsequently supply steam-engines, when the great railroad now commenced 
shall have been completed 1 . The chief, indeed the only fossil plant which we ob- 
served in this coaly deposit, is the Stigmaria Jicoides. As we have seen it both 
in the sands and shale associated with the coal, its position in Russia did not seem 
to us to afford evidence in favour of a theory which has recently become preva- 
lent in England, that this plant was a sort of gigantic marsh or lagoon creeper, and 
that all coal strata in which it was found were formerly jungles, marshes or masses of 
vegetation which subsided upon the spots of their growth. Again, the facts that the 
underlying Devonian beds are charged with fishes and marine shells, and that 
the Stigmaria sands resting on them are surmounted by another marine limestone, 
prevent our hastily applying this theory to the Russian coal deposits. We shall 
revert to this subject in our description of the coal-fields of the Donetz, where the 
evidences still more decisively prove a marine succession, and are therefore much 
opposed to such a theory. 
Lower Limestone of Tula and Kaluga . — This limestone affords the same clear 
horizon-line in the lower division of the Carboniferous system of the governments 
of Tula and Kaluga, as it does in the Valdai Hills and other parts of the north of 
Russia ; being very generally characterized by the presence of the Productus gigan- 
teus ( hemisphtsricus , Sowerby). In the cliffs opposite Peremishl (see woodcut in 
opposite page), and other places where we saw it, the limestone is a hard rock 
with conchoidal fracture, of grey, whitish and bluish colours, and is divided into 
beds from two to four feet thick. It is sometimes siliceous, and contains flattened 
concretions and obscure laminae of flinty chert and even of pure flint. At larusa 
on the Oka we found in it Productus giganteus, P. latissimus, P. punctatus, Euom~ 
phalus pentangulatus, Solemya primceva (Phill.) , Catenipora ( Harmodites parallelus, 
Fisch.), with Pinna , casts of Bellerophon, Turbo and Natica, and stems of Stig- 
maria ficoides. Again on the river Ocetre, in the government of Tula, the Pro- 
ductus giganteus occurs and is there associated with the P. striatus. At Alexina, the 
limestone overlying the coal and sands, contains the Productus giganteus with P. lo- 
batus (Sow.), Orthis (Spirifer) resupinata (Sow.), and 0. arachnoidea (Phill. affin.). 
In the neighbourhood of Kaluga this lower limestone expands and divides itself 
1 Two thousand poods, or about twenty-five tons of this coal were sent by Colonel Olivieri for trial to 
Moscow last summer, but some of the localities are too distant from water-carriage to render such supply 
economical. 
M 2 
