354 Dr. W. F. Hume — Notes on Russian Geology — 



In Eussia, then, we have three distinct regions distributed in 

 regular sequence from north to south, or more strictly lying in broad 

 curves bending from N.E. to S.W., and running parallel to the line 

 given by Murchison as the limit of distribution of glacial boulders. 



To the north and west of this boundary division lies the great 

 forest region, now much denuded by man ; but still, especially in 

 Lithuania, attaining magnificent proportions. Iminediately to the 

 south of this line lies the band, which shows a combination of 

 forest, small lake, and patches of steppe. This latter passes directly 

 but gradually into the true steppe region. 



Prof. Krasnov, after a comparison of the American and Russian 

 literature on this subject, concludes that the Black Earth region has 

 gone through three distinct stages : — 



1st. The stage of marsh formation, presumably the immediate 

 result of the melting of the ice-sheet. During this period there 

 would be a decided predominance of lakes and morasses, and a low- 

 lying marshy flora would be conspicuous. Trees and steppe-grasses 

 then only occupied the highest points. 



2nd. The stage of drainage, connected with poverty of the sub- 

 soil waters. This stage has been passed througb by the greater 

 part of the steppes and prairies. In their northern portions there 

 is still evidence of those water-holding depressions which on this 

 hypothesis must formerly have existed, and even such traces are 

 fast disappearing. These changes are accompanied by the im- 

 migration of a flora more suitable to a dry climate, and by the 

 formation of Black Earth. 



3rd. The wood stage, which is, as regards the south, as yet in its 

 infancy. As the steppe is denuded, so the woods, or more commonly 

 isolated trees in the first instance, advance along the valleys of the 

 streams, and occupy the ravines. My former paper on Loess really 

 dealt with the first, and part of the second above-mentioned stages. 

 It is noteworthy that but little is said about this great deposit in the 

 paper to which reference has been made above, although the general 

 sequence of events suggested by me has been to a large extent borne 

 out by Prof. Krasnov's results. 



The zoological studies carried out by Professor Nehring have still 

 further strengthened the position here being maintained. Since 

 1874 a series of papers have been written by him (see, for instance, 

 Sitz. Ber. der Gesell. Naturforsch. Freuude, Berlin, 1888-89-90, 

 p. 164) in which he has endeavoured to establish the existence of 

 steppe-characters in Central Europe during Pleistocene time. Here 

 again a triple division has been observed, each zone differing as 

 regards the animal remains contained in it. 



In the lowest, immediately succeeding true glacial deposits, occur 

 the bones of animals, now living chiefly in tundra regions and 

 higher latitudes, such as the Elk and Lemmiug. Besides these, the 

 Eeindeer, Arctic Fox, and Arctic Hare have been noticed. Not 

 only so, but fresh-water mollusca are very abundant, species of 

 Limnea, Paludina, and Pisidium, being especially noticeable. 



In the second, or zone of Loess proper, a typical steppe fauna 



