sort of belt. Particularly common are Payonari a paci f i ca (60% 

 occurrence) and Virgularia cystifera (4'Q-50%). The last species, 

 together with Protoptilum oriental e . is placed in the group of "coastal 

 deep-water forms" (Pasternak, 1973). The entire set of these 

 Pennatularia, elevated above the surface, is considered part of the 

 "epi fauna of soft bottoms." 



Of the irregular urchins, abundantly represented in the next 

 biocenosis, here we find only Pourtalesia laguncula beringiana , located 

 in the bathyal of the Sea of Okhotsk and Bering Sea and the northern 

 part of the Pacific Ocean (A. N. Mironov, 1974). 



This biocenosis includes both detritus-collecting forms and 

 sestonophages and predators. Characteristic are large Actinia (up to 50 

 individuals in a catch), the brachiopods Friella halli , the large 

 polychaete Aphrodite talpa , Sternaspis scutata , Terebellide stroemi , 

 Brada irenaia , Samythella neglecta , Travisia forbesi , T. pupa , 

 Augeneria bistnata , etc. Of the small bivalve mollusYs, we find 

 Delectopecten randolphi (occurrence about 60%), Nucula tenuis , N^. 

 cardara , Dermatomya sp., Myonera garetti (40%), Malletia truncata , H_. 

 pacifica , etc. The Echinodermata are represented primarily by a mass of 

 small Ophiuroidea: 0^. leptoctenia , Ophiophthalamus normani , Ophiolimna 

 bairdi , as well as Holothurioidea from the Stichopodidae and 

 Molpadiidae. The large Echiuroidea Prometor grandis and several species 

 of Pogonophora give this biocenosis an abyssal appearance. It is 

 therefore intermediate in nature between bathyal and abyssal biocenoses 

 in this region. 



The biocenosis Ophiura bathybia-Malletia cuneata- 

 Echinocrepis rostrata-Abyssaster tara is encountered in the upper 

 abyssal of the open portion of the Gulf of Alaska, at depths of 2240- 

 4740 m. At depths of about 2000 m, it borders with the above-described 

 biocenosis 0^. pallida- Y. beringiana . 



Probably, the biocenosis 0^. bathybia- M. cuneata is also located in 

 the adjacent portions of the abyssal northeastern part of the ocean. It 

 is restricted to soft, fine aleuritic and clayey silts, usually with 

 some pebbles and rounded pumice. The bottom temperature is 0.7-1.6°C, 

 averaging 0.9°C. The total biomass of the benthos in the biocenosis is 

 0.5-3.6 g/nr, averaging 1.5 g/m'^. This value is characteristic for the 

 northern eutrophic zone of the abyssal Pacific. Large silt-eaters are 

 characteristic for this biocenosis: various irregular urchins and small 

 Ophiuroidea. Small bivalve mollusks frequently form rather large 

 populations. The percentage of occurrence of even the leading forms is 

 low (not over 60%), due to the paucity of macrofauna. 



The leading forms are: Ophiura bathybia- -dozens or hundreds of 

 individuals in a trawl catch--and Malletia cuneata- -in places up to 30- 

 40 individuals. 



Of the larger forms, various irregular stars (ten species, up to 

 nine in one station) are important: Echinocrepis rostrata , 

 Cystocrepis setigera , Urechinus lovem , Echinosigra amphoFa fabrefacta , 

 Aporocidaris fragills , etc. 



215 



