PALAEOZOIC AND IGNEOUS ROCKS ON THE ISSETZ. 
363 
by strong reefs of rose-coloured granite. This system of micaceous rocks, occa- 
sionally exhibiting intrusions of granite, syenite, &c., continues to beyond the mill 
of Paulkin and the village of Mamniskaya (about twelve versts by the turnings 
of the Issetz), where it is succeeded by another class of rocks. The chief masses 
at Mamniskaya consist of bluish calcareous flagstones, with veins of white felspar, 
which apparently graduate into and alternate with a contemporaneous bedded 
trap-rock, not unlike the “ schaalstein ” of German geologists, so largely associated 
with the palaeozoic strata upon the rivers Lahn and Rhine 1 . These trappean 
rocks, increasing in volume as you descend the stream, have, however, a peculiar 
aspect. They are very felspathic, approach, here and there, to the character ot 
serpentine, contain much disseminated carbonate of lime, and after all leave the ob- 
server frequently in doubt, as to whether they really are sedimentary strata or not. 
At the hamlet of Tiomna they are boldly displayed. At Bielobor these bedded 
rocks (schaalstein), contemporaneous, we believe, with the limestones, rise up 
at a high angle against an intrusive porphyritic greenstone, which is succeeded 
by black limestones of considerable thickness, inclined at a very high angle to 
the west, and resting upon carbonaceous shale. These beds, the first in which 
we saw fossils in Siberia, unequivocally belong to the carboniferous limestone, 
for we found in them Productus gig as, Spirifer striatus (Sow.), and several charac- 
teristic corals. The schists which followed are contorted and afterwards thrown 
off around a nucleus of trappean amygdaloid, which is succeeded by a considerable 
development of highly crystalline greenstone, some of which, from the predomi- 
nance of felspar, may be called “ graystone ” 2 . These eruptive rocks occupy 
both banks of the river at Smolino (our station for the night), and also for some 
versts below it, where rising to rather greater altitude than the contiguous stiata, 
they constitute a rugged and picturesque defile, as at Bielobor. 
A point of compact felspar porphyry (eurite) protrudes among the blue schists, 
which are next observable, and which alternating with grits, often resemble the culm 
beds of Devonshire, like which they fold into numerous flexures dipping both to 
the east and west. We detected nothing in these schists but minute fossil plants 
—chiefly grasses— another point of analogy to the culm strata of Devonshire and 
the “ flotz- lehrer-sandstein ” of the continent ; whilst the occurrence of Productus 
gigas and P. pustulosus, in an adjacent rock at Zairnskaya, furtliei indicated the 
continuance of the carboniferous deposits. At Kadinskoi, however, a limestone 
1 See Trans. Geol. Soc. vol. vi. p. 249. 
2 See Scrope, Geol. Trans, vol. ii. p. 214. 
