292 Th. Mortensen. 



spimis and Ophiopus arcticus, however, are widely distributed also 

 in the warm area, especially the former; according to Grieg 

 ("Michael Sars" Asteroidea.) it is, however, possible to distinguish 

 the specimens from the warm area as a separate variety. Hijmenaster 

 pellucidus is recorded also from the Azores (Perrier), but probably 

 erroneously (Koehler. Monaco. XXXIV. 1909. p. 94). Upon the 

 whole, all the above named species are typical cold-water forms. 



The Atlantic abyssal fauna is represented by the following 

 species: 



Ophiopleura aiirantiaca Tromikosoma Koehleri 



Ophiomusium Lijmani Pourialesia Wandelt 



Ophiacantha abyssicola Aëropsis rostrata 



Ophiactis abyssicola Brisaster fragilis 



Phormosoma placenta, \ar. Sigsbei Lœtmogone violacea. 



To these will doubtless have to be added a considerable num- 

 ber of Atlantic Deep-Sea forms. The Davis Slrait and the Danmark 

 Strait are the direct continuations of the Atlantic Deep-Sea, a pair 

 of large gulfs of the Atlantic, as it were; it is then not at all sur- 

 prising to find here species occurring otherwise down to the West 

 Indies, as e. g. Phormosoma placenta, var. Sigsbei and Ophiomusium 

 Lymani, the latter species being known to occur also in the Pacific 

 Ocean. 



The difference between the Atlantic and the Arctic Deep-Sea 

 faunas occurring in the Greenland Seas is distinct enough as seen 

 by the two above lists. There is certainly some intermingling of 

 the tw^o faunas. Thus we may add Pontaster tenuispinus and Ophiopus 

 arcticus to the list of the Atlantic species, and on the other hand 

 Ophiacantha abyssicola and Ophiactis abyssicola might be added to 

 the list of species of the Polar Sea, as both these species occur also 

 within the cold area, especially the latter. But even if we agree 

 that the three species: Pontaster tenuispinus, Ophiopus arcticus and 

 Ophiactis abyssicola are really common to both the warm and the 

 cold area ( — that Ophiacantha abyssicola is a typical atlantic form, 

 only just touching the borders of the cold area, is beyond doubt — ), 

 the difference between the fauna of the Polar and the Atlantic deep 

 sea is very striking. It is an established fact that we have here 

 two quite distinct faunas meeting in the deep Avaters off 

 Greenland, just intermingling a little at the boundaries between 

 their respective areas. 



The fauna of the deep basin of the Baffin Bay is quite unknown 

 as yet. It is still an unsolved problem, whether it is a branch of 

 the Atlantic deep-sea fauna or is more related to the arctic abyssal 



