794 P. T. CLBVE, SOME ATLANTIC PLANKTON-ORGANISMS. 



August. Rare SW. of Tceland. Färöe Channel. Abun- 

 dant at Spitzbergen, 77° N. 12°— 23° E. — East Greenland, 

 65° N. 35° — 36° W. — Irish Channel, rare. — Tlie Azores, rare. 



September. Very sparingly SW. of Cape Farewell and 

 W. of Greenland {Q6° N. 55° W.). 



et ober. S. of Ireland. 



November and December. Rare at the Azores. 



Thalassiosira gravida Cl. in 1898. 



March. At 74° N. 5° W., 58° N. 6° E. and 40° N. 69° W. 



April. Common NW. of Iceland (66° N. 24° W.) and not 

 rare S. of Iceland. Rare W. of the Shetlands and at 42° N. 47° W. 



May. Rare at 73 N. 10° W. Enormously abundant bet- 

 ween Jan Mayen and East Greenland, from 72° 30' N. 13° 9' W. 

 to 70° 25' N. 13° 40' W. (salinity 34,26 to 34,40 p.m., temperature 

 — 1,3 to + 0,4), rare at 68° 29' N. 17° 11' W. (salinity 33,66 

 p.m., temperature — 0,5), common from 68° N. 21° W. to 67° 

 N. 25° W. — Rare SW. of Greenland, but common from Cape 

 Farewell to 63° N. 54° W. 



June. Very common at 73° N. 5° W. and in the Den- 

 marks Sound (from 66' N. 28° W. to 67° N. 29° W.), rare S. 

 of Iceland — W. of Greenland, from 63° N. 56° W. to 69° N. 

 54° w. — Abundant at 59° N. 51° W. 



August. Sparingly N. and W. of Spitzbergen — E. of 

 Greenland (65°— 66° N. 36°— 37° W.), W. of Greenland, at 

 66° N. 55° W. 



September. Davis Strait at 69° N. 53° W. (common) 

 and 65° N. -55° W. (rare). 



This species has the same distribution in the northern 

 Atlantic as the other trichoplankton-forms, but is more sensitive 

 to changes in the salinity, so it does not spread so far to the 

 south. Nevertheless it has been found some years both in the 

 south of the North Sea and at Plymouth. Interesting is its 

 abundancy south of the entrance to the polar basin. 



