142 



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



fasciatum, Gibbula tumida, Trichotropis conica and others may be pointed out 

 and among the Brachiopoda Waldheimia cranium. 



To the east of the North Cape the boreal forms are considerably decreased 

 and replaced by representative forms of the colder-water fauna. Instead of the 

 above-mentioned sedentaria, Protula media, Filigrana implexa, Pseudopota- 

 milla reniformis, Potamilla neglecta begin to preponderate here ; Waldheimia 

 cranium is replaced mainly by Terebratulina septentrionalis and Rhynchonella 

 psittacea. Among the warm-water sea-urchins Brisaster fragilis and Echinus 



Fig. 55. Distribution of six main benthos biocoenoses in 

 Barents Sea: / Southwestern; // Central; /// Eastern 

 shallows; IV Eastern (coastal); V Northern (deep); 

 VI Northern (shallows) (Brotzkaya and Zenkevitch with 

 Filatova's additions). 



esculentus still remain and of the molluscs Astarte montagui and Saxicava 

 arctica begin to prevail here. 



East of North Cape a number of boreal forms are found in large amounts 

 as mollusc shells. 



The benthos biomass of the littoral sand and rock floors varies from 120 to 

 400 g/m 2 . 



Of the shallow (not deeper than 80 to 100 m) benthic groups of the Murman 

 sublittoral the biocoenosis of the large bivalves Modiola modiolus, Pecten 

 islandicus and Mactra elliptica are of great interest ; they have a definite north- 

 boreal character and in the last few years they have developed greatly on the 

 Murman coast owing to a considerable rise in temperature. 



They reach their highest development in Danish waters and off Iceland and 

 the Faroe Islands. These communities grow poorer in quality and quantity 

 as one proceeds northwards and eastwards. Off the Murman shores both 



