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termine the exact place of these beds in the geological series, nor to 
point out their true relations to the adjacent masses. Many of the 
fossils have since been described by the native authors, Pander and 
Eichwald, and recently some very characteristic forms by M. de 
Buch. 
The Silurian deposits consist in ascending order of blue clay, inter- 
mediate grit, and overlying limestone, &c. In the first of these no 
organic remains have yet been found; and the intermediate sand- 
stone or grit is alone distinguished by a remarkable form unknown 
in western Europe (the Ungulite), which the authors consider to be 
nearly allied to Orthis. They likewise discovered in this grit one 
small shell resembling a Pecten. In the limestones, and certain 
overlying flagstones first described on this occasion, organic remains 
abound; and they agree well in the leading characters on which the 
Silurian system was established, viz. that the forms of Trilobite, 
Orthoceratite, and Orthis are distinct from the types of the overly- 
ing members of the palzozoic series. 
The most prevalent fossils are the Orthoceratites vaginatus, Asa- 
phus expansus, Illenus crassicauda, the peculiar Crinoidean Sphero- 
nites (allied to the Ischadites of the Upper Silurian rocks), and a 
vast profusion of many species of Orthis. Although, upon the whole, 
the Silurian fossils of Russia differ more than those of Sweden from 
British species of the same age (as might indeed be expected from 
their more remote distance), certain shells are identical with those 
published from England; among which are enumerated, Leptena 
depressa (L. rugosa, Dalm.), Leptena sericea, Lingula Lewisii, Orthis 
canalis (O. elegantula, Dalm.), &c.; and according to M. Eichwald, 
two or three species of Trilobites*. 
With the exception of some very trivial dislocations in the low 
hills south of St. Petersburgh, the Silurian rocks are so uniformly 
horizontal, that in the fine quarries on the banks of the Wolkoff, the — 
authors were able to prove a difference of 2° or 3° to the S.S.E, 
only by pouring water on the surface of the rocks. 
These Silurian deposits occupy the islands of Oland, Gothland, &c. 
in the Baltic, and trend along the shores of Esthland in a broad 
band from W.S.W. to E.N.E., till they are lost under vast heaps of 
granitic detritus between the lakes Ladoga and Onega. Near the 
latter, these deposits are deflected to the north, and there meet with 
great ridges of trappean rocks, which run from N.N.W. to 8.8.E. 
In that region all the deposits are in a metamorphic condition; the 
limestones present no distinct traces of fossils; and the authors ha- 
ving satisfied themselves that there was no chance of observing any 
further evidence of a descending order between such rocks and the 
great primarized granitic chain of Scandinavia and Russian Lapland, 
the boundary of which they coasted, confined their attention to the 
ascending order of the strata, which is clearly exhibited on the banks 
of the Wolkoff and at other places. 
2. Old Red, or Devonian System.—That the pie strata are the 
* See Professor Kichwald’s work, published since the authors’ visit to 
Russia, entitled ‘ Silurische-Schichten-system in Msthland.’ 
