THE KARA SEA 249 



so in the southeastern shallow parts ; this stands in agreement with the sug- 

 gestion of the increased amounts of carbon dioxide in the regions of brown 

 mud. Z. Shchedrina (1938) and T. Gorshkova (1957) recorded Ammo- 

 baculites cassis, Verneulina polystropha, Spiroplectammina biformis, Elphi- 

 dium gorbunovi, Reophax curtus and others in the shallow areas. Shchedrina 

 relates Trochommina turbinate, Nonion labradoricum, N. orbicular e, N. stelliger, 

 Hormosina globulifera, H. ovicula, Saccoriza ramosa, Trochammina globuli- 

 formis, Elphidium incertum and others to the group of the brown mud forms. 



On the brown muds the main forms are the Foraminifera Saccorhiza ra- 

 mosa and Harmosina globulifera, the sponge Polymastia uberrima, the coe- 

 lenterate Actinium metridium, members of the Eunephthya genera and the very 

 large coral Umbellula encrinus, the polychaetes Nephthys ciliata, Nicomache 

 lumbricalis, and Thelepus cincinnatus, the Sipunculidae Phascolosoma minuta, 

 the crustaceans Mesidothea sabini, M. sibirica, Sabinea septemcarinata and 

 Sclerocrangon ferox, the pantopoda Colossendeis proboscidea, the gastropod 

 mollusc Neptunea curta, the bivalves Pecten groenlandicus and Astarte 

 crebricostata and especially various echinoderms, also the asteroids Pon- 

 taster tenuispinus, brittle stars Ophiopleura borealis, Ophioscolex glacialis, 

 Ophiocantha bidentata, Asterias panopfa, A. lincki, Hymenaster pellucidus, 

 the holothurians Molpadia and Trochostoma, and the lilies Poliometra 

 prolixa. 



A comparatively large number of forms which rise above the bottom, such 

 as Metridium, Umbellula, Eunephtya, Colossendeis, Poliometra are char- 

 acteristic of the whole of this fauna. The very large size of most of the above- 

 mentioned forms is remarkable ; on the other hand the predominance of the 

 'parachute' type of forms — Polymastia, Mesidothea, Pecten, Pontaster, 

 Hymenaster, Gorgonocephalus and others — is also interesting. These three 

 factors are evidently the ways of adaptation to soft-floor conditions. 



It is difficult to understand how the echinoderms with their solid calcareous 

 skeletons can reach such a high level of well-being on the brown mud, since 

 the carbonates are not retained in the floor itself, and we have never found 

 any accumulation of shell gravel in the areas of the occurrence of brown mud ; 

 on the contrary a rapid process has been observed of the solution of the 

 shells of dead molluscs and an evident shortage of calcium carbonate in the 

 living ones. 



The fish population of the brown mud, which is very small, is also remark- 

 able. It consists usually of small-sized members of the Cyclopteridae, Zoar- 

 cidae and Cottidae families (the most common ones are Liparis coefoedi, 

 Icelus bicornis and Triglops pingelii). However, even these small-sized fish 

 are extremely rarely found. None of the rich selection of commercial fish of 

 the Barents Sea are found on the brown mud. They are kept away also by the 

 low temperature of the bathymetric layer all the year round (below zero). 

 Only the long rough dab (Hippoglossoides platessoides) lives here in small 

 numbers, as immature specimens or mature dwarfs. 



The biocoenotic groups of the Kara Sea benthos were thoroughly studied 

 by Z. Filatova and L. A. Zenkevtich (1957). These workers have distin- 

 guished seven basic biocoenoses (Fig. 107) which have been combined into 



