Ad. s. Jensen: The Selachians of Greenland. 37 



in part even in shallow water; they penetrate with decreasing frequency into the 

 upper part of the Deep Norwegian Basin. 



Of the Greenland rays mentioned in the Hst Raja hyperborea occurs everywhere 

 in the Deep Norwegian Basin ; here it goes down into some of the greatest depths where 

 trawling has ever been carried on (1309 fm.) and upwards the boundary of its distri- 

 bution coincides with the boundary layer between the cold polar water and the over- 

 lying warm Gulf Stream water (cf. Chart fig. 12) '). 



When I wrote my paper cited above I included Raja hyperborea among the 

 special forms of the Deep Norwegian Basin, as at that time it was only known from 

 the depths of the Norwegian Sea. In the interval howewer it has been found by the 

 Russian investigations in the eastern Barents Sea'), which is in itself not surprising, 

 as this region has ice-cold water at the bottom (cf. Chart fig. 12). 



Returning now to West Greenland it will be recalled, that Raja hyperborea proved 

 to be common in the northern part of colonized Greenland, namely from the northern 

 part of Disko Bay up to Upernivik (cf. Chart fig. 12). This occurrence was also 

 unknown, when I wrote the paper mentioned, but if we consider the hydrographical 

 conditions this discovery is not surprising either. The arm of the sea, which separates 

 Greenland from northern America, like the arms between Greenland and Europe, is 

 divided into two basins distinct in hydrographical regards by a ridge, which lies ca. 

 250 — 300 fathoms under the surface and extends right across the Davis Strait almost 

 at 67° N. L., namely: (1) the southern part of Davis Strait up to the ridge between 

 Greenland and Baffins Land, which is filled from the bottom and upwards to a depth 

 of ca. 100 fm. below the surface with Atlantic water with high temperatures (ca. 

 2,5° — 5° C); (2) the northern part of Davis Strait, north of the ridge mentioned, 

 and Baffins Bay, where the bottom-water at the greatest depths has temperatures 

 below 0°C.^) (nearest the Greenland coast however, in depths of ca. 150 — 350 fm., we 

 find a mixed product, with temperatures of about 1° C, of polar water and warm 



') The occurrences marked on this chart are based on the results of the expeditions with 

 "Vøringen", the "Triton", "Ingolf", "Michael Sars" and "Thor". On the cruise of the "Michael 

 Sars" in 1902 I had the opportunity, thanks to the kindness of Dr. Johan Hjort, of making 

 personal observations and can thus guarantee, that on this expedition R. hyperborea was ex- 

 clusively taken on the sea-bottom with negative temperatures, though R. Collett in his elabora- 

 tion of a part of the fish material from this expedition states that R. hyperborea was also taken 

 where the bottom temperature was positive. Unfortunately several errors of a similar, regret- 

 table kind have slipped into Collett's report (Rep. Norw. Fishery and Marine Invest., II, 1905, 

 No. 3). 



2) Exped. f. wissenschaftlich-praktische Untersuchungen an der Murman-Kuste, I, 1902, von 

 N. Knipowitsch, pp. 426, 448, 466; Faune de la Russie, Poissons par L. S. Berg, vol. 1, 1911, 

 p. 103. 



3) Axel Hamberg: Hydrografisk-kemiska lakttagelser under den svenska Expeditionen til 

 Grønland 1883. Bihang til Kgl. Svenska Vet. Akad. Handlingar. Bd. 9, No. 16, 1884 (p. 53). 



