182 



THE GEOLOGIST. 



stones of the steppes are stated to exhibit the finest examples 

 of a transition from the pleiocene to the post pleiocene series, 

 the organic remains in the uppermost beds being undistin- 

 guishable from the shells of the Caspian. Of this most 

 recent deposit, Russia, as the authors observe, possesses 

 peculiarly two distinct accumulations, one characterised by 

 an arctic fauna, now living in the North Seas, and the other 

 by a fauna of temperate zones, or that of the Caspian. In 

 reviewing the phenomena presented by the vast territory 

 which passed under their survey, the authors dwell on the 

 uninterrupted successi<:>n of conformable marine deposits 

 throughout nearly the whole of the fiat regions of European 

 Russia, or the non-intercalation of terrestrial, freshwater, and 

 estuary formations, connecting the absence of such strata 

 with the total want of intrusive or other igneous rocks, as 

 -well as all evidence of violent disturbance and inconformabi- 

 lity, except in the coal-field north of the sea of Azof. The 

 cause of these peculiarities, or the absence of plutonic rocks, 

 is considered by the authors to have also influenced the 

 lithological structure of the formation, some of the oldest of 

 the Silurian strata having quite as recent an aspect as the cre- 

 taceous or tertiary beds. 



Another point of great zoological, as well as geological 

 interest, connected with the singular structure of Russia, is 

 insisted upon in the memoir. Each formation is clearly 

 marked by its distinct suit of organic remains, even in those 

 cases where there is no unconformability or abrupt transitions 

 between one series of rocks and the next in succession ; and 

 therefore, Mr. Murchison observes, that this distinction, 

 especially in the Silurian, Devonian, carboniferous, and Per- 

 mian systems, cannot be due to violent operations, which 

 destroyed one race of animals to make way for another ; and, 

 consequently, that the theory founded on such a supposition, 

 and deduced from the investigation of countries which pre- 



