524 



DEPTHS OF THE OCEAN 



«-: 



occur occasionally in immense quantities. Crustaceans are 

 represented by a characteristic deep-sea form, namely the 

 isopod Glyptonotiis megaluriis, nearly related to a form that occurs 

 in the arctic region in shallower waters ; pycnogonids by 

 Ascorhynchus abyssi; and molluscs by 

 Pecten frigidus (see Fig. 369), Nephmea 

 mohni, Natica batJiybi, etc. There are 

 also some deep-sea sponges, prominent 

 amongst which are the Hexactinellids; 

 although not regularly distributed over 

 the Norwegian Sea, they are found in 

 great quantities to the north of Spits- 

 bergen at a depth of 1000 metres, 

 where they and another group (Tetrax- 

 onia) constitute the most characteristic 

 portion of the fauna. Outgrowths on 

 their under sides enable them to hold 

 fast to the soft bottom, which is littered 

 with silicious spicules from dead 

 sponges.^ Romer and Schaudinn have 

 doubted whether the deep-sea fauna 

 of those northern latitudes is to be 

 considered zoo-geographically as a part 

 of the fauna of the Norwegian Sea deep basin, or whether 

 it belongs to a separate faunal area, the deep polar basin ; deep- 

 sea sponges have, however, been subsequently found in 

 quantities farther south (lat. 72 23' N., long. 

 13 50' W.) at a depth of 2000 metres.- 



The forms limited exclusively to the abyssal 

 region, or at any rate only very exceptionally 

 occurring in shallower waters, are not the only 

 ones which characterise the Norwegian Sea deep 

 basin, for we find regularly also a number of other 

 forms met with on the slopes in the cold area.^ 



Just as the Norwegian Sea deep basin has 

 its own (even though rather few) character- 

 istic forms, which do not ascend to the arctic plateaus but con- 

 stitute a typical deep-sea fauna, so, too, the plateaus have a 



^ Romer and Schaudinn, op. cit. p. 49. 



^ Kolthoff, Till Spetsbergen och 7iord'6stra Gronland, igoo, pp. 212-213. 



'^ The "Michael Sars" found at about 2000 metres the echinoderms : Bathybiaster 

 vexillifer, Ophiocien sericetim, and Pourtalesia ; the mollusc : Siphonodentaliiiin vitretim ; the 

 crustaceans : Bythocaris leucopis and Hymenodora glaciaUs ; tlie pycnogonid : Nymphon 

 robustum ; the worm : Lwtibrinereis, etc. The tube-worm, Myriochele, with its fine sand-tube, 

 belongs to the forms which occur in quantities in the depths of the Norwegian Sea. 



Fig 



Elpidiaglacialis, Thfel. Magnified 

 (After Stuxberg. ) 



Fig. 369. 

 Pccte?i frigidus, 

 Jensen. ' ' Michael 

 Sars," 1900. 



