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



In the diluted southeastern part of the Laptev Sea only 73 species of even this 

 meagre fauna have been encountered (Coelenterata 5, Porifera 4, Polychaeta 

 8, Bryozoa 7, Mollusca 19, Crustacea 17, Pantopoda 2, Echinodermata 2, 

 Tunicata 7, and Pisces 5). 



The high Arctic forms are overwhelmingly predominant in this fauna. 



Near the river estuaries either brackish-water or the most euryhaline marine 

 forms are predominant: the crustaceans Gammar acanthus loricatus, Gam- 

 marus wilkitzkii, Mesidothea entomon, Mysis oculata var. relicta, the poly- 

 chaetes Polydora quadrilobata and Euchone papillosa, the molluscs Portlandia 

 arctica, the fish Myoxocephalus quadricomis. Farther out to sea Mesidothea 

 sabini, M. sibirica, Acanthostepheia malmgreni and others become gradually 

 predominant. 



Popov notes a remarkable similarity between the fauna of the south- 

 eastern part of the Laptev Sea and that of the Ob- Yenisei Bay of the Kara Sea : 

 in both cases the main part of the benthos consists of Mesidothea sibirica, 

 M. sabini var. robusta, Onisimus botkini, Portlandia arctica siliqua, Gammarus 

 wilkitzkii, and Pseudalibrotis birulai. 



Qualitative composition of fish fauna 



The composition offish according to their families also deserves our attention 



{Table 113). 



Table 113 



No. of No. of 



species Percentage species 



Salmonidae 7 184 Agonidae 2 



Cottidae 9 23 Osmeridae 2 



Zoarcidae 7 18 > 77 Cyclopteridae 1 



Liparidae 5 13 Pleuronectidae 1 



Gadidae 2 5/ Clupeidae 1 



Acipenseridae 1 Gasterosteidae 1 



Total 39 



The high Arctic and brackish-water forms are even more prevalent here 

 than in the Kara Sea. 



The fauna of the deep-water northwestern part of the Laptev Sea and that 

 of the passages between the Severnaya Zemlya Islands must be even greater 

 in variety. As in the Kara Sea large numbers of Arctic deep-water and inter- 

 mediate warm-layer fauna of the deep trench rise to lesser depths. Some 

 Barents Sea forms in small numbers reach the western part of the Laptev Sea. 



