Report on the Echinoderms of Xorth-East Greenland. 293 



fauna. The third alternative — that it is a fauna peculiar to itself — 

 is not very probable, in view of the comparative small area this 

 basin occupies. The Polar Deep-Sea is so sharply separated from 

 the Baffin basin through the shallow waters in Smith Sound and 

 the other sounds to the North of Baffinland that a direct communi- 

 cation of the deep-sea fauna of the Polar Sea with that of the Baffin 

 Sea is excluded. If a nearer relation between the deep-sea faunas 

 of .these two regions proves to exist it must be due to a more 

 direct communication in a former period. Most probably, however, 

 the fauna of this deep basin will prove to have been derived from 

 the Atlantic fauna occurring in the Davis Strait. It has been proved 

 through the researches of the "Tjalfe" ^ that below the cold surface 

 water a bottom stream of warm Atlantic water (ca. 4° C.) passes 

 northwards over the Holstenborg ridge into the Baffin Bay, making 

 its influence felt at least as far North as the Umanak Fjord, where 

 the bottom-temperature (at 700 m) is ca. 1° С Probably the influence 

 of this warm water wall be felt over the whole of the Baffin basin, 

 and in accordance herewith it may be suggested that the fauna will 

 be derived from the Atlantic fauna of the Davis Strait. 



The Atlantic archibentlial Echinoderm-fauna of Green- 

 land is represented by the following species: 



Psilaster andromeda Pedicellaster typicus 



Leptoptychaster arcticus Ophiacantha anomala 



Pentagonaster granulans Ophioscolex purpureas 



Hippasteria phrygiana Molpadia blakei, var. grönlandica. 



It is a prominent feature of this list that most of the species 

 included occur in other places, especially at the Norwegian Coast, 

 in considerably smaller depths than the 200 m here taken as the 

 upper limit of the archibenthal region. Thus Psilaster andromeda, 

 Pentagonaster g r anularis, Hippasteria phrygiana and Pedicellaster typicus 

 are known there from so small a depth as 20 m, Leptoptychaster arc- 

 ticus and Ophioscolex purpureus from ca. 60 m. At the Greenland 

 coast, how ever, they are not known from above the 200 m line, and 

 it seems fairly certain that they do not occur at all above that 

 depth, viz. within the belt where the polar water makes its influ- 

 ence felt. They thus represent a very conspicuous Atlantic (boreal) 

 element in the Greenland fauna. That these species occur at so 

 low depths at the Norwegian coast is in accordance with the 



1 Ad. S. Jensen: Indberetning om Fiskeriundersøgelserne ved Grønland i 1908— 

 1909. (Foreløbig Meddelelse om de fra Briggen "Tjalfe" foretagne hydrografiske 

 Undersøgelser i Sommeren 1908^1909 ved J. N. Nielsen). Beretn. og Kund- 

 gørelser vedrørende Kolonierne i Grønland. Nr. 2, 5. 1909. 



