580 
RESUME AND CONCLUSION. 
taken place upon the surface of the globe, whether as respects the most ancient or 
more modern accumulations. 
In the first place, we have indicated the existence over large tracts in Scandi- 
navia, the Baltic provinces and northern Russia, of those Lower Silurian strata, 
which by extensive examination of various countries, have been found to contain 
the earliest vestiges of animal life. This point has, indeed, been rendered singularly 
clear in Sweden, where Lower Silurian rocks, perfectly identified with those of their 
typical regions in the British Isles, rest at once on crystalline or azoic rocks of 
antecedent date, in which the remains of all organized beings, if such there ever 
were, have been entirely obliterated. Representing as elsewhere the lowest recog- 
nizable stage charged with organic matter, the Lower Silurian rocks of Sweden and 
Russia teach us, that among the earliest animals known to us were crustaceans, 
with eyes 1 suited to the recesses of the seas in which they lived, and that these, 
with certain JMollusca, Zoophytes and Crinoidea, which have long since passed 
away, were associated with marine fucoids, the latter being, as far as we know, the 
only vegetables of which there is a trace in this protozoic group. 
The next or Upper Silurian stage of Russia and the Baltic Isles is remarkable for 
the close analogy of all, and the identity of a great number of its mollusks and corals 
with those of the same period in the British Isles. In it, however, no traces of fishes 
have been found ; a negative fact which induces us to remark, that whilst the Lower 
Silurian formations have nowhere offered the fragment of a vertebrated animal, and 
that a very few small fishes of peculiar form have only been found at some localities of 
the Upper Silurian deposits in England (chiefly in their highest beds), the system 
must, on the whole, be viewed as one almost void of this great class of organic beings. 
The Silurian system of the northern countries of Europe is indeed closely 
analogous to that of Great Britain ; and its examination has taught us, that 
wherever the sediments of the same age in the two regions resemble each other 
in lithological texture, such similarity is accompanied by a close approximation 
and frequent identity in the associated organic remains. 
The survey of Russia has next strikingly confirmed the fact, that the Devonian 
or Old Red system of English geologists is the second great natural group of 
deposits in the ascending order ; and there, as in the British Isles, it is the great 
fossil “piscina,” in which the mass of the earliest fishes has been preserved. The 
1 See Dr. Buckland’s masterly description of the structure of the eyes ot Trilohites, “ Sixth Bridgewater 
Treatise,” vol. i. p. 396. 
