622 



BIOLOGY OF THE SEAS OF THE U.S.S.R. 



Fig. 292. Quantitative distribution of Nereis in Northern Caspian in 



June 1948: above 50 (7); 50-25 (2); 25-10 (5); 10-5 (4); below 5 (5) 



(Birstein and Spassky, 1952). 



0-60 to 0-70 g/m 2 , while at 700 m it falls to 002 g/m 2 . In the Northern Caspian 

 the mean benthos biomass is 7-59 g/m 2 even at 150 m. As in the Central 

 Caspian the Central and Southern Caspian benthos has a preponderance of 

 molluscs (90 per cent of the total biomass in the Central Caspian, 98 per cent 



Fig. 293. Distribution of organic substances in the soils of the Northern 

 Caspian as percentages (Yastrebova, with data of Gorshkova added) : 

 above 3 (I); 3-2 (2); 2-1-5 (5); 1-5-1 (4); 1-0-5 (5); below 0-5 (6); 



trace (7). 



