566 ^- Stephensen. 



to have been derived from the Atlantic fauna occurring in the Davis 

 Strait". Among the Crustacea Mortensen's hypothesis seems to 

 apply only to the plankton forms, not to the bottom-animals. As 

 the following lists will show, namely, this region has 6 endemic 

 species, 37 (perhaps only 25) species common with the cold area of 

 the Polar Ocean but only 2 species (Pandalus borealis and Pseudomma 

 parvum) common with the deep Atlantic. If we place the boundary 

 between the boreal and arctic regions at 0°, as seems reasonable, 

 the geographical boundary between these two regions at West Green- 

 land cannot be drawn at the ridge, but somewhat more to the 

 north, namely, north of Umanak Fjord (ca. 71° N.), as we can still 

 notice the influence of the Atlantic water there, the bottom-water 

 having a positive temperature (J.N.Nielsen in Ad. S.Jensen: Ind- 

 beretning om Fiskeriundersøgelserne ved Grønland i 1908. Beret- 

 ninger og Kundgør, vedrør. Kolonierne i Grønland, No. 2, 1909, 

 pp. 24 — 27). For practical reasons, however, we may continue to 

 place the faunistic boundary at the ridge mentioned. The case of 

 Pandalus borealis and Pseudomma parvum, which at West Greenland 

 are found to the north as far as Umanak Fjord, seems to be the 

 only one, which at the present moment w^uld require the zoogeo- 

 graphical boundary to be moved further north. 



The Arctic deep-water fauna may be divided into 3 groups 

 according to the distribution of the species; A. species endemic to 

 West Greenland, B. species from the cold area of the Polar Ocean 

 and C. species common to both regions. 



lA. Species endemic to the cold deep basin at West 

 Greenland. 



There are only 6 of these, namely: 



Hippomedon abyssi. Unciola laticornis. 



Eusirus Tjalfiensis. — crassipes. 



Ischyrocerus (Podocerus) nanoides. Anceus cristatus. 



Hippomedon abyssi is widely distributed in the Davis Strait N. of 

 68°36' N. (20—25) 100-280 fm. (H. J. Hansen 1887 and "Tjalfe"). 



Eusirus Tjalfiensis has been taken at 7041' N., 52^07' W„ 386 fm., 

 800 m. wire out ("Tjalfe"). 



Ischyrocerus nanoides is only known from 71°10' N., 58°56' W- 

 200 fm. (H. J. Hansen 1887). 



Unciola laticornis: 69°16' N., 58^8' W., 339 m. (H.J.Hansen 1887). 



Unciola crassipes: 66°22' N., 57°]6'W., 686 m. ("Tjalfe") and 71° 

 10' N., 58°56' W. 200 fm. (H. J. Hansen 1887). 



Anceus cristatus: 72°32' N„ 58°51' W. 116 fm. (H.J.Hansen 1887). 



