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



populations of the Mediterranean, Black and Azov Seas are not isolated from 

 each other, but to a certain extent are constantly mingling with each other, 

 forming only local ecological varieties. Maljatzky does not consider anchovy 

 as a relict in the Black Sea. In exactly the same manner V. Zalkin (1938) does 

 not consider the Black Sea dolphin Phocaena relicta as an individual species. 

 It is only a sub-species, and is likewise not a Tertiary relict but a form which 

 arrived in the Black Sea recently. 



The characteristic features of the distribution of fauna in the Bosporus 

 and the Sea of Marmora, conditioned by a gradual general decrease of salinity 

 from the Dardanelles to the Bosporus and by the existence of two currents in 

 the Bosporus and the region round it — the upper Black Sea current and the 

 deep, much more saline one — were established by the researches of Ostroumov 

 in the nineties of the last century. The boundary between the two currents 

 sinks gradually as one approaches the Black Sea. Off Constantinople it lies 

 at a depth of 20 m, and at the entrance into the Bosporus at 50 m. As a result the 

 upper-layer fauna has a Black Sea character, and that of the deeper layer a 

 Mediterranean one. A. Ostroumov (1893-6) has recorded 60 forms, also 

 found in the Black Sea, in his collection of the coastal fauna in the Bosporus 

 area. On the other hand, in deeper layers the fauna has a markedly Medi- 

 terranean character. Already at a distance of 1 8 km from the entrance into the 

 Black Sea, 49 per cent of the molluscs and more than 50 per cent of the amphi- 

 pods were found to be extraneous to the Black Sea. Sea lilies, sea urchins, sea 

 stars, the Siphonophora Dimophyes, and eight-rayed corals were found 

 here. Off the Prinkipo Islands 70 per cent of molluscs did not belong to the 

 Black Sea. 



The surface plankton of the Sea of Marmora is also under considerable 

 influence from the dominant Black Sea forms, but below 20 to 30 m it has a 

 typically Mediterranean character. 



Qualitative-biocoenotic characteristics of zoobenthos. More than 50 years 

 ago S. Zernov, in his work 'On the study of the life of the Black Sea' (1912), 

 gave a very full picture of the qualitative-biocoenotic distribution of the Black 

 Sea bottom-living fauna. The scheme given by Zernov has been neither 

 changed nor substantially supplemented by further researches. It appear ass 

 Table 181, and Figs. 209, 210 and 211. 



Biocoenoses of supralittoral and pseudolittoral. Having reconsidered the 

 question of the existence of a 'littoral' zone in the Black Sea, L. Arnoldi 

 (1948) came to the conclusion that 'from the biological point of view there is 

 no theoretical difference between the flood- and ebb-tide phenomena as such, 

 and the fluctuations of the sea-level, which depend equally on the flood- 

 tides of cosmic origin and on the seiche (wind-induced tides)'. Confirming the 

 existence of a littoral zone in the Black Sea, Arnoldi distinguishes a Black Sea 

 type of littoral, using the word 'pseudolittoral' for it. A supralittoral (a zone 

 washed only by the surf) lies above the pseudolittoral. 



O. Mokievsky, having very carefully studied the littoral fauna of the western 



