4*92 Geological Society. 



Orthoceratite, and Orthis are distinct from the types of the overly- 

 ing members of the palaeozoic series. 



The most prevalent fossils are the. Orthoceratites vaginatus, Asa- 

 phus expansus, Illtenus crassicauda, tne 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, Leptcena 

 depressa (Z#. rugosa, Dalm.), Leptcena sericea, Lingula Lewisii, Orthis 

 canalis (0. 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 th§ 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 S.S.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 inferior strata are the 

 true equivalents of the Silurian system, was determined not only by 

 their aspect and fossil contents, but by their being overlaid by other 

 rocks which are completely identical with the " Old Red System " 

 of the British Isles, as defined by Mr. Murchisonf. This system is 

 of great extent in Russia. It passes from Livonia by the lakes of 

 Ilmen and the Waldai Hills, and is extended over a vast region to 

 the N.E., where it constitutes a large portion of the shores of the 

 White Sea. This system consists of flagstone, clays, marls, corn- 

 stones and sandstones, the whole bearing a considerable resemblance 

 to some red deposits of the same age in our isles, but differing by 

 containing copious salt springs and much gypsum. It was the oc- 

 currence of so much salt and gypsum that led previous writers to 

 consider these deposits an equivalent of our new red system, which, 



* See Professor Eichwald 's work, published since the authors' visit to 

 Russia, entitled ' Silurische-Schichten-system in Esthland.' 

 f See Silurian Researches, p. 165, and Table with the Map. 



