10 



PLANKTON-TYPES. TRICHO-PLANKTON 



PLANKTON-TYPES. 



In the following report on the seasonal distribution of the 

 Atlantic plankton organisms I again use the signs (\ D, .S, 7, 

 which denote, as in my previous papers on this matter, Chceto-, 

 Desino-. Styli- and Tricho-plankton, Nm, Ns and Ng, Southern, 

 Northern and Arctic neritic plankton. The new sign Nt denotes 

 Tropical neritic plankton. The Sira-plankton in my former publi- 

 cations may be disregarded for the Atlantic, as this type corresponds 

 partly to T and partly to Ng. The Sira-plankton which appears in 

 the Skagerak, as a rule in February and March, contains neritic 

 arctic species intermingled with boreal species and some forms, 

 which belong to the Tricho-plankton. As this kind of plankton is 

 very characteristic for the Skagerak, it may be useful to keep the 

 name for the said plankton in the Skagerak. 



In the following lists the letters B, I, M, P, R and W denote the 

 Baltic, Indian Ocean, Mediterranean, Pacific, Red Sea and White Sea. 



I. Tricho-plankton. I have arranged most species of this 

 type thus: 



Tricho-plankton (Arctic oceanic species) T. 



^ . ., Mean _. Distribution 



Limits , Mean , .. 



, . ., tern- ,. .. outside 



Lat. .\. salinity ,, ,,, ,. 



perature the Atlantic 



Fritillaria borealis 81° — 50° 7.4 34.oo Antarctic. 



Boreophausia inermis 78' — 68^ 3.4 35.09 



Nyctiphanes norvegicus 75° — 61°(42) 0.,; 35. lo 



Thysanoessa longicaudata 85° — 48° 6.o 34.84 



Euthemisto libellula 85°— 40" 2.b 34.8,i 



Parathemisto oblivia 85°— 45° 2.o 34.i5 



Calanus finmarchicus 85°— 30° 7.s 34 so Antarct. M.P.I. 



C. hyperboreus 85°^58" 2o 34.98 



Chiridius armatus 85° — 65° O.o 34.8i 



Euchseta norvegica 85° — 58" 2 3 35. 12 



Metridia Jonga 85°— 58° O.7 34.94 



Onceea conifera 78°-62° ()., 34.98 Lv^Lfan islands 



0. minuta 78°— 38° 5.,, 35.02 M. 



