SECTION OF THE RIVER VOLKOF. 
29 * 
(nob.). The ravines in the calcareous plateau are also rich in those peculiar 
bodies ( Cystidece of Von Buch) which characterize the Lower Silurian rocks of 
Scandinavia and Russia, of which the Sphceronites ( Echinosphcerites ) aurantium and 
8 - pomum are the most abundant. With these are occasionally associated Echino- 
encrinites angulosus, E. striatus, together with Cryptocrinites cerasus and Hemicos- 
mites pyriformis (the two latter being new species described by Von Buch). Of 
these the Echinosphcerites aurantium, with some minute Orthidce and the Favosites 
Petropolitanus 1 (Pand.), seem to be characteristic of the upper beds exposed in the 
hills of Duderhof. 
On the Tosna, a little above the village of Nikolskaya, the cliffs present in one 
vertical section the whole series from the top of the blue clay at the base, through 
the Ungulite sandstone and bituminous schist to the chloritic beds, or bottom of 
the overlying limestone. In the latter we collected many specimens of the small 
Orthis obtusa and O.parva (Pand.), associated with the Leptcena imbrex (Sil. Syst.), 
and the Asaphus expansus. 
So far, then, the different members of the same system are developed at those 
well-known localities; but before the period of our first visit, no natural section 
had been discovered which clearly exposed the relations between this Lower Silurian 
group and the next overlying formation. This we first effected by an examination 
of the banks of the river Volkof, as explained by the following woodcut. 
6 
a ‘ Blue clay of the low country near the mouth of the river, b. Cliffs, 80 to too feet high, of Ungulite grit and sandstone, which to the south of 
starai Ladoga are overlaid by bituminous schists (e), and the lower and upper limestone { d , e and /) ; the latter occupying the cliffs at Petropavlosk 
(the Upper Silurian group being absent), is at once surmounted by rocks ( g ), which form the base of the Devonian system. 
We may here offer some details of the succession of these calcareous strata. 
After passing over the low country occupied by the blue clay and the cliffs com- 
posed of Ungulite sandstone, the banks of the Volkof show the superposition of 
the lowest beds of the limestone to the bituminous schist and Ungulite sandstone. 
Such an order occurs about three versts above Starai Ladoga, and on the right bank 
of the river opposite the hamlet of Isvosk. 
1 Mr. Lonsdale shows that this coral, so characteristic of the lower rocks of Russia and Scandinavia, and 
also, as we believe, now found in the Lower Silurian of North Wales, is a Chcetetes (see Appendix A.). 
E* 2 
