INVERTEBRATE BOTTOM FAUNA 



515 



necessarily indicate mortality from extraordinary circumstances, 

 but merely an accumulation, from a considerable area, of 

 individuals whose deaths were due to natural causes. Although 

 certain indications along the coasts of our own and other lands 

 would appear to justify us in regarding currents as a means of 

 conveyance, we know far too little about the matter to be able 

 to discuss it with any profit.^ 



In my remarks regarding the edge of the Norwegian 

 depression I endeavoured to show that the fauna of this part 

 of the North Sea differs from that in its more central parts (see 

 p. 506) ; for this difference, however, the depth, nature of the 



Fig. 357. 

 Nephrops tioti'egicus, L. Reduced. (After Bell. ) 



bottom, and temperature cannot be held solely responsible. 

 This difference holds good also for the continental plateau beyond 

 the 100 metres curve. The " Michael Sars " captured in 1 10 to 

 150 metres : the crustaceans Nephrops norvegicus (see Fig. 357), 

 Geryon tridens, Sabinea sarsi, Pontophilus spinosus, Pandalus 

 brevirostris, Hippolyte pusiola, Caridion gordoni\ the pycnogonids 

 Nymphon stroiui and N. mixtitm ; the echinoderms Hippasterias 

 plana (according to Plate rarely found on the Great Fisher 

 Bank), Solaster endeca, Pteraster viilitaris (two small specimens), 

 Ophiocten sericeimi (quantities of young specimens) ; the snail 

 Scaphander punctostriatiis, etc. None of these forms (except 

 one individual of Nyynphon stromi) were met with in the central 

 portion of the North Sea. Three of them in particular 



1 Compare Heincke, "Die Mollusken Helgolands," Wissensch. Meeresttnterstich. Komni. f. 

 Untersuchimg Deutsch. Afeere, Neue Folge, Bd. i, pp. i^o et seq. 



