GENERAL CHARACTERISTICS OF FAR EASTERN SEAS 717 



pronounced in some areas of the West Indies and the seas of the Malayan 

 Archipelago . . . thus, for example, the sea urchin Pvgmaeoeidaris prioni- 

 gera, usually found at depths of 2,000 to 3,000 m in the Molo Strait of the 

 Malayan Archipelago, has been recovered from a depth of only 69 to 91 m. 

 The same has been observed of the deep-water family of sea urchins Echino- 

 thuriidae and Aspidodiadematidae, the Porifera Hyalonema and Farrea and 

 the crabs Ethusina and others. ... In that respect the region of the Banda Sea 

 and the Key Islands is particularly remarkable, since an apparent mass ascent 

 of the deep-water fauna to shallow depths is observed there. . . . The plateau 

 on which the Key Islands are situated lies in shallow water and the temperature 

 of the water falls below 10° to 13°. A mass ascent of deep-water fauna to the 

 shallows is observed within the area of this plateau, which falls sharply away 

 into the great depths of the Banda Sea. This deep-water fauna consists of 

 most varied species of sea urchins, holothurians, starfish, glass sponges and 

 others. ' 



Such a peculiarity in the vertical distribution of deep-water fauna may pos- 

 sibly be connected with the manner of its formation. 



It is therefore even more astonishing that in the Bering Sea, where in general 

 several deep-water forms have a tendency to rise to the upper horizons 

 (E. F. Gurjanova, 1936), and in the neighbouring Sea of Okhotsk Pogono- 

 phorae were found only in a few cases at depths of less than 1 ,400 m (one 

 case) and 1,693 m (two cases), and that usually they do not rise in the sea 

 above 2,800 to 3,000 m.* Of the three Far Eastern Seas the highest number of 

 Pogonophorae species has been recorded in the Bering Sea (1 1), seven of which 

 appear, so far, to be endemic to it. Of the five species recorded in the Sea of 

 Okhotsk only Siboglinum plumosum can provisionally be regarded as endemic. 

 So far only one species has been discovered in the Sea of Japan, Oligobrachia 

 dogieli, which had obviously penetrated from the Sea of Okhotsk where it 

 lives at a depth of 119 to 572 m. Eight species of Pogonophorae have been 

 described for the Kuril-Kamchatka trench, four of them endemic to it. Three 

 endemic species have been found in the Japanese trench. 



Echiuroidea (mainly of the family Bonelliidae) form a most original and 

 characteristic element of the abyssal and ultra-abyssal fauna of the north- 

 western part of the Pacific ; there are eleven species of them (L. Zenkevitch, 

 1957, 1958) belonging to seven genera. Such an abundance of Echiuroidea is 

 not known for any other region of the ocean. Echiuroidea are extremely 

 poorly represented in the Galathea collection ; there was only one specimen 

 each among the material gathered by Challenger and Ziboga. There were none 

 at all in the Valdivia collection. One of its species may be considered as a 

 bipolar form. Echiuroidea {Prometor benthophila) are very rarely found on the 

 eastern side of the Pacific Ocean. A group of ultra-abyssal forms can be clearly 

 distinguished among the Echiuroidea (Table 290). 



As a result of the researches of the Vityaz into the deep-water fauna it was 

 found possible to widen considerably the limits of distribution in the depths of 

 many groups of fauna (Table 291). 



* In the Antarctic also at a depth of 3,000 m. 



