INVERTEBRATE BOTTOM FAUNA 



523 



S^. 



having tins ; its arms are united to each other throughout their 

 whole length by a skin attachment. The sea-tooth (scaphopod), 

 Sip hono dent alium vitrezcm, is also a very widely distributed form. 

 In the Norwegian Sea deep basin beyond 2000 metres the 

 conditions seem as a rule to be less favourable for the develop- 

 ment of an animal-life abounding in species, as already alluded 

 to by Sars in his report on the first cruise of the Norwegian 

 North Atlantic Expedition. The bottom at these great depths 



consists of Globi- 

 gerina (or Bilocu- 

 lina) ooze, offering 

 no foundation for 

 attached forms. 

 Only a few species 

 are limited to 

 these profound 

 depths, as the 

 majority occur 

 also in the shal- 

 lower areas of the 

 Arctic region, or 

 are met with on 

 the slopes of the 

 Norwegian Sea 

 deep basin. 



One of the 

 most character- 

 istic deep-sea 

 forms is a sea-lily, 

 Bathycrinus car- 

 pent eri, that at- 

 taches itself to 

 the soft bottom 

 by means of the root-like ramifications issuing from its stalk 

 (this form has a near relation, Rhizocrinns lofotensis, which 

 occurs in the deeper parts of the boreal region). Another 

 characteristic echinoderm is a sea-slug, Kolga hyalina, which is 

 never found in depths less than 2000 metres. Elpidia glacialis 

 (see Fig. 368), too, must be considered a characteristic sea-slug 

 of the Norwegian Sea deep basin, though it may from time to 

 time be met with in the north at lesser depths. These two 

 holothurians belong to a remarkable group, with few though 

 very large feet arranged in rows on either side ; they 



Fig. 367. 



Arctiirus baffi?ii. Sab. With young. 



(After Wyville Thomson. ) 



Fauna of the 

 abyssal area 

 of the 

 Norwegian 

 Sea. 



