The Abyssal molluscan fauna of the Norwegian sea and its relation to other faunas

Abstract About 90 000 specimens of mollusks, from depths between 2 500 and 4 000 m in the Norwegian Sea, have been determined. They belonged to 25 species. Five species are described as new, Cuspidaria centobi (Bivalvia), Anekes undulisculpta, Crinolamia dahli, Cylichna lemchei (Gastropoda), and Siphonodentalium laubieri (Scapho-poda). Two of these, Anekes undulisculpta and Crinolamia dahli are type species of the new genera in which they are placed. The other species have been critically examined from a taxonomical point of view, as have the species previously recorded from the Polar Abyssal Basin, but not present in the Norwegian Sea. Some information is given about the feeding, anatomy, and larval development of the species. The origin and development of the fauna are discussed, and it is concluded that at least a part of the fauna is a reminiscence of the old North Pacific fauna that lived in the Polar Basin before this was disconnected from the North Pacific by the formation of Bering Strait. These species have since then diverged only very sligthly. It is also concluded that the abyssal parts of the Norwegian Sea and the Polar Basin form a homogeneous Zoogeographic area, with a highly endemic fauna.