SILURIAN FOSSILS OF RUSSIA. 
36 * 
of the masses are accompanied (as might be expected) with corresponding pecu- 
liaiities in the distribution of their organic remains. Whilst the lowest stratum 
in Sweden is, for the most part, a sandstone, and in Russia a shale (both void of 
any vestiges of animal life), we no sooner ascend into the overlying sandstone of 
the latter country, than we find that its fossils bear a general analogy to some 
of the Lower Silurian rocks of England and America. The Ungulite or Obolus 
which occupies this sandstone has, indeed, its parallel in the similarly constituted 
horny shell, Lingula attenuata (Sil. Syst.), which is in some places copiously disse- 
minated in the Lower Silurian rocks ; and in America, where one of the very lowest 
fossil rocks is a sandstone, the analogy, as we have before mentioned, is still more 
striking. Although the Orthidae with simple plaits, common in some of the very 
lowest Lower Silurian beds of Snowdon and North Wales, are not found in this 
Russian sandstone, we have but to ascend from it into the next fossiliferous mem- 
ber, the 1 pleta limestone, and we detect such forms as the Orthis calligramma, 
0. o? thambonites and O. nioneia ; all belonging to the division of that genus which 
is typical of rocks of this high antiquity. From the community of their fossils, 
no doubt whatever can exist, that the great lower limestones of Norway and Sweden, 
with their Trilobites and Orthoceratites, are precisely of the same age as the pleta 
limestone of the Russians. But here it is well to observe, that although, upon 
the whole, there is a close resemblance between the lower fossiliferous limestone 
of the two countries, there are marked distinctions of detail. Thus in Sweden, 
the bed beneath the great limestone in which the earliest vestiges of animal life 
have been seen, is a black bituminous and aluminiferous stratum with calcareous 
courses, in which peculiar Encrinites, Trinuclei and Paradoxides or Olenus are 
associated with masses of fucoids ; whereas in Russia this band, or one upon the 
same horizon, being much less developed, and on the whole much less rich in cal- 
careous matter, and rarely affording traces of fucoids, is to a great extent barren 
of organic life. As soon, however, as we mount to the great fossiliferous band, 
in which calcareous matter has been equally diffused in the two countries, the 
synchronous deposits of Scandinavia and Russia are found to be alike loaded 
with the same group of fossils, and to a great extent the very same species. 
Thus, among the Orthoceratites, the 0 . vaginatus and 0 . duplex, which are by far 
the most abundant, though unknown in the British Isles, have even there their 
equivalents in the rarer species with lateral siphuncles. In Scandinavia, however, 
where more typical British species of various Lower Silurian genera exist than in 
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