of the Ural Mountains. 127 



southern prolongation of this line of upheaval that the Permian red 

 sandstones and limestones of Gre-beni and Orenburg are thrown 

 into anticlinal positions, the axis of which is also parallel to that of 

 the adjacent older rocks. For reasons' hereafter adduced, it is in- 

 ferred that this anticlinal was formed subsequent to the chief ele- 

 vation of the chain. 



Devonian Limestones, fyc. — The Devonian rocks of the North Ural 

 are seen on the banks of the Tchussovaya in the form of limestones, 

 grits and schists, which pass into the lower carboniferous limestone, 

 the latter being always in highly inclined, sometimes in very con- 

 torted and even inverted positions, the younger rocks dipping under 

 the older. These Devonian limestones much resemble, in their dark 

 colour and subcrystalline aspect, those of South Devon in England, 

 and they contain fossils characteristic of this division both in the 

 British Isles, in Belgium, Prussia and the Eifel ; but though perfectly 

 identified both by position and contents with the Devonian rocks of 

 the flat regions of Russia, the Uralian strata are as dissimilar from 

 them in external aspect as the rocks of the same age in Devonshire 

 are from the old red sandstone of the north of Scotland and of 

 Herefordshire or Brecon in England. Nor are these Devonian rocks 

 on the western flanks of the Ural separated from the lower car- 

 boniferous limestone by any band of sandstone and coal as in the 

 northern parts of Russia in Europe, but the grey limestone of the 

 overlying group is at once succeeded by the dark limestone of the 

 other, both undergoing the same flexures, and both forming parts 

 of one great palaeozoic series. 



In their prolongation to the south, the limestones of this Devo- 

 nian group thin out and inosculate with a considerable development 

 of red sandstone, grit, fine conglomerate and schist, in some parts 

 resembling the old red sandstone of the Highlands. A peculiar 

 mineral character of these Devonian limestones is, that they retain 

 their black colour even when in the state of dolomite. 



Silurian Hocks. — The schists and flagstones which underlie these 

 limestones are considered to be of Silurian age ; with these strata 

 are associated beds of limestone for the most part concretionary, 

 and which are well developed on the banks of the Serebrianka from 

 the zavod of Serebriansk to near its mouth. Among the predomi- 

 nant fossils of this group and amid numerous corals, the Terebratula 

 prisca (Atrypa qffinis, Sil. Syst.) is clustered together in great masses, 

 as in the Ludlow rocks of England, and with it are associated the 

 remarkable Leptcena Uralensis and other new species. The same 

 descending sequence cannot be.so well seen in many parts of the 

 North Ural, as on the banks of the Serebrianka. 



Immediately, however, to the east of the water-shed (viz. from 

 Bogoslofsk to Nijny Tagilsk and Neviansk), broken masses of 

 limestone, insulated amid plutonic rocks, are charged with large 

 Pentameri, closely approaching to the Pentamerus / Knightii of 

 the upper Silurian rocks, and associated with Orthis, Terebratula 

 and other fossils, which, from collections sent to him, M. de Buch 

 has classed as Silurian forms (see Beitriige der Geb. Form, in Russ- 



