ECHINOIDEA. II. i^g 



regions etc., as is done excellently by Appellof (Op. cit); but in this more summary review of the 

 main regions there is no reason for entering on these minor subdivisions. 



It is the merit of Professor H. F. E. Jungersen to have shown definitely that also in the 

 deep-sea separate regions may be distinguished.' Already on the Expedition of the ^Lightning- in 

 1868 Wyville Thomson was struck with the i^hysical and faunistic differences in the Faroe-Channel 

 between the <cold area» and the warm area» (.(Depths of the Sea»); the discovery of the submarine 

 ridge across the Faroe-Channel thus far explained the fact that two so different areas could exist 

 close by one another without a mixing up of their characters. Rut the ■ Ingolf»-Expedition brought 

 evidence for the highly interesting fact that the whole of the deep basin of the sea North of 

 Iceland (the «Norwegian Sea») forms a separate deep-sea region, distinguished by its low (negative) 

 bottom-temperature and by a peculiar deep-sea fauna, quite distinct from that of the Atlantic deep sea 

 South of Iceland. A submarine ridge across the Denmark Strait, from Greenland to Iceland, with a 

 depth of only ca. 300 fathoms, another ridge between Iceland and the Faroe Islands with about the 

 same depth, and finally the ridge across the Faroe Channel (330 fathoms) limit this large cold area 

 from the deep sea of the Atlantic South of Iceland, where the bottom-temperature is considerably 

 higher (the warm area). The «cold area-> of Wyville Thomson is only the southernmost extension 

 of the large cold deep-sea area of the Norwegian Sea. — Probably also other parts of the deep sea 

 will prove to form definite regions; but our knowledge is still insufficient to state that definitely. 



The Arctic littoral region comprises the whole of the Arctic Sea along the Northern Coasts 

 of Europe, Asia and America, being thus circumpolar; it extends towards the South as far as the ice- 

 cold polar water extends. On the European side the Gulf Stream restricts its limits very much, so 

 that it does not pass beyond a line from about the South end of Nova Zemlja to the South end of 

 Spitsbergen, except along the Northern Coast of Russia, where it proceeds to the White Sea. All 

 Greenland and the North American Coast down to Cape Cod belongs to this region. — Only two 

 species of Echini occur in this region, viz. Strongyloccnfrotus drobachiensis and Echinarachnhis parma, 

 the latter only at the American Coast; both of them proceed far towards the South, beyond the Arctic 

 region, Str. drdbacliicnsis to the Channel on the European, to New Jersey on the American side, 

 Echinarach. parma to Chesapeake Bay. As pointed out by Doderlein (Op. cit.) both of them probably 

 must have come from the Northern Pacific, wandering towards the East from the Behrings Strait. While 

 Echinarachnius parma has still not reached beyond the American Coast, not even to Greenland, Str. 

 drobachiensis has reached as far as Taimyr on the Siberian Coast; between Taimyr and the Behring 

 Strait it has not been found. It is thus not strictly circumpolar. — It would be very interesting to 

 learn if Ecliinarachiiiits paniia does really occur along the whole North Coast of North America. It 

 is known as far North as Labrador (Belle Isle Strait) on the Atlantic Coast, as far as Point Belcher 

 on the Alaskan Coast. The fact that it does not occur at Greenland might perhaps indicate that it 

 is not found along the whole of the North American Coast. In that case the explanation of its 

 occurring in two isolated places, on the Atlantic and on the Pacific Coast of North America, would 

 probably have to be sought for in the oscillations of the climate after the Ice Period. It has been 



I Fra «Ingolf >-Expeditioneu. BemEerkuinger oiu Dybbavsfauiiaeu og dens Fordeliug i de uordlige Have. Geografisk 

 Tidsskrift Bd. XIV. 1897. 



23* 



