291 



thrive at the southern West-Greenland? I do not believe it. 

 On another occasion I have recently compiled all the information 

 at hand regarding the distribution of Yoldia arctica^). It 

 appears from this that this small bivalve demands in order to 

 thrive a slight yearly variation in the temperature of the 

 water, namely from its absolute minimum which is about at 

 — 2° 6 С to ca. -|- 2° 5 С Such low temperatures occur however 

 just in the South-Greenland fjords at the depths at which 

 Yoldia arctica lives, viz. at ca. 3 — 118 fms. We know this 

 from the measurements of temperature taken with Negretti and 

 Zambra's inverting-thermometer by J. A. Ü. Jensen and by R. 

 R. J. Hammer. I allow myself here to copy the temperature 

 statements for the summer : 



Place. 





Date. 



Depth in fms. 



Temperature 



Nagsugtok, 67° 40' 



N.2) 



t6. VII 1879. 



5 



2-8° G. 



— — 





— 



10 



11° - 



— — 





— 



20 



0-9° - 



— — 





— 



30 



10° - 



— — 





19. VII 1879. 



10 



11° - 



— — 





— 



20 



04° - 



— — 





— 



30 



0-2° - 



— — 





■ — 



40 



- 01° - 



Niakungunak, 64° 53' 



N.3) 



24. VII 1885. 



20 



2-3° - 



(= Fiskefjord) — 





— 



50 



0-1° - 



— — 





— 



92 



— 0-3° - 



— — 





25. VII 1885. 



20 



1-6° - 



— — 





— 



30 



1-3° - 



— — 





— 



50 



0-3° - 



— — 





— 



100 



— 0-3° - 



Godthaabs-Fjord^) 





7. VIII 1885. 



50 



1-4° - 



— 





— 



100 



0-4° - 



— 





4. IX 1885. 



50 

 inn 



2'2 ° - 



1-1 о _ 



In the winter, 1879 — 80 the following temperatures were 

 taken in Jakobshavn's Ice Fjord ^): 



^) Jen sen, 1. с 



2) Medd. 0Ш Grønland, II, 1881, p. 207—208. 



3) Ibid. VIII, 1889, p. 83—84. 

 *) Ibid. p. 97. 



5) Ibid. IV, 1883, p. 28. 



