36 
SILURIAN FOSSILS OF RUSSIA. 
us to infer, that to the east (in the government of St. Petersburgh) , where the ele- 
vation has been more powerful, it has also acted at a somewhat earlier period ; for 
whilst in the eastern tracts watered by the Siass, the Volkof and Ishora, the pleta 
or lower limestone is at once surmounted by true Devonian strata, so as we proceed 
to the east the intermediate Pentamerus limestone is interpolated between the two 
systems ; and, finally, in the Baltic Isles we have the full development of unequi- 
vocal Upper Silurian strata, all traces of which, physical or zoological, are excluded 
in the government of St. Petersburgh. 
Silurian Organic Remains . — Recurring to the works of Eichwald and Pander, 
and availing ourselves of the light recently thrown upon some of these forms by 
\ on Buch, it will be our effort to point out in the second volume the zoological 
resemblances and differences between the Silurian and other palaeozoic fossils of 
Russia, and their analogues in Scandinavia and Western Europe. In the mean- 
time we may, however, offer some general remarks upon the distribution of the 
Silurian fossils. 
When the remains from St. Petersburgh, Esthonia, and the Russian Baltic Isles 
aie laid before a geologist versed in paleozoic forms, he at once pronounces them 
to belong to the same system in the series, as that which has been named Silurian 
in other parts of the world, for he finds them to consist, as a whole, of the same 
profusion of Orthidee, Leptaenae, Trilobites and Orthoceratites. Further, if his eye 
is sufficiently accustomed to the distinctions indicated by these fossils, he will at 
once see, that the system thus generally portrayed, is divisible into the two stages 
adverted to, and which are the equivalents of those which have been recognised in 
Western Europe and America. Of the Lower Silurian fossils of Russia a few onlv 
are, it is true, absolutely identical with forms of the same age in the British Isles • 
but the mass of them is essentially the same as that of the main land of Scandi- 
navia ; which region, being intermediate between England and Russia, is found to 
contain a considerable number of forms common to deposits occupying the same 
position in both the other countries. 
On the present occasion we shall simply adduce some of the leading evidences 
concerning these two groups ; and first, as to the Lower Silurian. 
The earliest formed palaeozoic strata in Russia, as in Scandinavia, are charac- 
terized by fucoids only, and to this extent there is an agreement ; but in examining 
the ascending series, some differences in lithological characters are found to cha- 
racterize its subdivisions in the two countries, and these variations in the structure 
