Report on the Echinoderms of North-East Greenland. 291 



nated as the archibenthal region, and the depths below 500 fathoms 

 as the abyssal region. This division seems very natural for the 

 Greenland seas, the littoral region thus coinciding with the belt, 

 where the polar water reigns. For the deep sea to the North of the 

 Danmark Strait there is no reason for distinguishing both an archiben- 

 thal and an abyssal region, the fauna being of a rather uniform 

 character below the littoral region; in the Davis Strait there may 

 be reason to distinguish between the archibenthal and the abyssal 

 region, though, upon the whole, these two regions are not nearly so 

 sharply distinguished as is the littoral region from the two deep- 

 sea regions. — It may be noticed that the species are here reckoned 

 to the one or other region after their main occurrence; because a 

 deep-sea species now and then occurs in the littoral region (or 

 inversely a littoral species in the deep-sea regions) it is not counted 

 among the littoral (or abyssal) species. The limits of the three regi- 

 ons are here rounded to 200 and 1000 m. 



We may first take the deep-sea species, the problems connected 

 with them being clear enough and easily understood. They are 

 easily seen to form two quite distinct faunas, viz. an arctic 

 abyssal fauna, occupying the deep sea to the East of Greenland, 

 north of the ridge across the Danmark Strait, and an Atlantic 

 abyssal fauna, occurring in the Davis Strait and probably round the 

 whole of South Greenland, towards the ridge in the Danmark Strait. 

 The arctic archibe n t h al-abyssal fauna is represented by 

 the following species: 



Bathycrinus Carpenteri Ophiopleura borealis 

 Pontaster tenuispiniis Ophiopus arcticus 



Bathybiaster vexillifer Poiirtalesia Jeff'reysi 



Tylaster Willei Myriotrocluis Théeli 



Korethraster hispidus Molpadia arctica 



Hymenaster pellucidus Kolga hyalina 



To these also Elpidia glacialis will probably have to be added. 

 Several of these species also occur in places with warm bottom tem- 

 perature (Pontaster tenuispinus, Bathybiaster vexillifer, Korethraster 

 hispidus, Ophiopleura borealis, Ophiopus arcticus), but it seems to be 

 mostly in the boundary regions between the cold and the warm area, 

 where the temperature is more or less fluctuating. ^ Pontaster tenui- 



' Grieg ("Michael Sars" Ophiuroidea. p. 13) is of opinion that the limit between 

 the cold and the warm area is not represented by the temperature ° but b}' 

 that of -\-2 or +2*5°. I am not inclined to think this suggestion correct. We 

 will have to recognize that some species are more eury therm than others; this 

 difference in their relation to temperature may well account for the ditïerences 

 in their distribution, some being restricted within the limits of the one or other 

 area, while others may transgress these limits more or less extensivel}'. 



