of the Ural Mountains. 133 



nothing to retract. On the contrary, by adding to their previous lists 

 a great number of typical organic remains well known in Western 

 Europe, they are still more convinced of the accuracy of their first 

 classification, and of the existence of large zones of Silurian, Devo- 

 nian and carboniferous rocks, clearly separated from each other by 

 their order and their imbedded fossils. 



The newly discovered dome of Devonian rocks in the centre of 

 European Russia is a feature of great importance, in explaining 

 the difference between the mineral basin to the north and that to 

 the south of it. The carboniferous system, the most widely extended 

 deposit of Northern Russia, has now been subdivided into stages, 

 each characterised by its fossils ; and it has been clearly shown, that 

 the most productive of the coal-bearing strata in the Russian em- 

 pire, viz. those of the southern steppes, are associated with the 

 mountain limestone ; whilst the uppermost member of the system, 

 or coal-measures, which is so rich in coal in Western Europe, if 

 indeed it exists, is nearly unproductive in Russia. 



The next great group of rocks in ascending order, is that which 

 has been elaborated in considerable detail under the name of the 

 Permian system, and which, as already shown, is to be considered 

 as a vastly expanded equivalent of the zechstein and associated beds 

 of Germany and the magnesian limestone of the British Isles. This 

 system is rendered much more important by its fossil contents in 

 Russia than by any remains which have been discovered in it in 

 other parts of Europe ; for not only does it contain, like the zech- 

 stein of Germany and the magnesian limestone of England, the re- 

 mains of thecodont saurians and certain fishes (Palaeonisci), but 

 also a fauna much more copious in other classes, and a flora in- 

 finitely more rich than any which had been previously made known 

 as pertaining to rocks of this age. This flora is shown to be of in- 

 termediate characters between that of the carboniferous system 

 and the plants which have been published as typical of the trias. 



The Permian system is also of high interest in setting before us 

 the example of wide accumulations impregnated throughout great 

 thicknesses with copper, and as this matter has manifestly been de- 

 rived from the mineral masses of the adjacent Ural, so is it inferred 

 that these mountains constituted dry land on which the plants in 

 question grew, and that the latter having been washed down into these 

 Permian deposits were there rendered the nuclei of the copper ores 

 which are arranged around them. The thin layer of kupfer schiefer 

 of Germany may be considered as the miniature representative of this 

 great metalliferous deposit, whilst in its large masses of gypsum, the 

 Permian deposits exceed even the zechstein on the south of the Hartz*. 

 The Jurassic system of Russia reposes on the Permian and older 

 rocks without clear evidence of the existence of any part of the 

 Triassic group, there being no traces of the muschelkalk limestone 

 nor yet of the keuper $ and it is with doubt even that the authors 



* The authors use the term " Permian" in reference to Russian deposits 

 only, and they by no means seek to interfere with the general use of the 

 word "Zechstein," which has been so long sanctioned by the highest Ger- 

 man authorities. 



