T. BELT ON THE STEPPES OF SOUTHERN RUSSIA. 859 



The fact that the water that then covered so much of Europe 

 carried such a quantity of mud in suspension for hundreds of miles 

 is an additional argument in favour of the conclusion that it was 

 not salt ; for we know that sediment is rapidly precipitated from 

 saline solutions. These turbid waters appear to have been unsuitable 

 for living creatures ; for the shells contained in the Upper Diluvial 

 Clay are either those of land mollusks or of freshwater ones that live 

 in marshy places or small pools. Their presence in the loess of the 

 great valleys maj 7 be easily accounted for by supposing that they 

 were washed down from the slopes of the hills by heavy rains ; but 

 their distribution over the plains near Wolochisk cannot be thus 

 explained. As I found angular pieces of limestone in the same clay 

 at Wolochisk that contained the shells, I think it likely that shore- 

 ice breaking up in the spring, and carrying shells that had dropped 

 off the reeds growing around the margin of the lake, may have been 

 the agent of distribution, especially as the Succinea oblonga, which 

 was likely to abound in such situations, is much the commonest 

 shell in the clays of the Steppe. 



We have still to inquire what became of the Aralo-Caspian fauna, 

 and how it was preserved during the time of the deposition of the 

 diluvial clay. It was certainly then banished from the areas of the 

 Danube and the Black Sea, the water there being both too muddy 

 and too fresh for its existence ; but probably to the east different 

 conditions prevailed. The currents from tho north, carrying in 

 suspension the fine detritus from the glaciers of Scandinavia and of 

 Central Europe, would be all directed towards the outlet through 

 the Bosphorus, and their muddy waters would not extend far to the 

 east. We may suppose that somewhere around the southern shores 

 of the Caspian, or still more to the east, the Aralo-Caspian fauna 

 found a refuge. There are numerous salt springs now around the 

 shores of the Caspian ; and in areas thus made saline those species 

 that require brackish water might be preserved. 



Dr. Gwyn Jeffreys has kindly examined the shells I collected 

 in the fluviatile, diluvial, and recent deposits, and furnished me 

 with the following lists of the species. The recent ones from the 

 river Bug and the sea of Azof are given for comparison with those 

 from the fluviatile beds and the lower part of the diluvial clay. 



No. 1. Upper part of Diluvial Clay at Podwolochisk : — 



Succinea oblonga, Braparnaud. 



Helix hispida, Linne. 



Helix ericetorum, Midler ; var. minor, Jeffreys. 



Helix pulchella, Mull. 



Pupa marginata, I) rap. 



No. 2. Lower part of Diluvial Clay at Podwolochisk : — 



Succinea oblonga, Brap. 

 Helix hispida, L. 

 Pupa marginata, Drop, 



