PLANKTON-TYPES. STYLI-PLANKTON. DIDYMUS-PLANKTON. 19 



Mean Outside 



Limits tempe- Mean jho 



rature salinity Atlantic 



Chsetoceros volans 4°S. — 77°N. 14.i 35.09 



Corethron hystrix 7°N.— 76°N. 10.* 35.i2 North P. 



Coscinodiscus sol 32°S.— 57°N. 15.6. 35.8o M. R. P. 



Dactyliosolen antarcticus 35°N. — 62° N. 11.? 35.37 Antarctic. 



D. hyalinus 32°N.— 47°N. U.i 35.oo 



Hemidiscus cuneiformis... 29°S.— 66°N. 20.8 35.56 M. I. 



Navicula mefnbranacea... 21°N.— 43°N. 15.2 35.47 R. I. P. 



Rhizosoleriia alata 30°S.— 66°N. ll.g 35.39 M. I. P. 



R. corpulenta 5°S.— 64°N. 15.7 35.s6 North P. 



R. styliformis 26°S.— 80°N. 12.o 34.79 M. P. 



It will be seen that many have a very wide range of distribu- 

 tion, several from the Cape of Good Hope to Spitzbergen. Many 

 occur in the Mediterranean, some in the Pacific, and some in the 

 Indian Ocean. Among these species there is also one Baltic species, 

 Evadne Nordmannii, wich I should have placed among the boreal 

 species, had it not, according to Hansen's statement, been found in 

 the Gulf of Guinea. 



A certain number of species, which occur usually in the coast- 

 regions of the temperate Atlantic, form a kind of plankton that is 

 related to the Styli-plankton in the same way as the arctic neritic 

 plankton to the Tricho-plankton. They constitute the plankton-type 

 I have called Didymus-plankton or Southern neritic plankton. 



The following list contains such forms as belong to this type. 



Didymus-plankton. (Temperate neritic species.) Nm. 



Podon intermedius 40°N.— 70°N. 



Acartia bifilosa 6°S.— 63°N. 



Euterpe acutifrons 40°S.— 51°N. 



Gyttarocylis serrata 33°S.— 58°N. 



Tintinnopsis campanula. . 9°N. — 58° N. 

 Bacterjastrum varians ... 7°N. — 58° N. 



Biddulphia mobilensis ... 21°N.— 62°N. 



Cerataulina Bergonii 7°N.— 80°N. 



Mean Outside 



tempo- l^«an the 



rature salinity Atlantic 



12.S 35.4 



14.4 

 11.3 



34.94 

 34.88 



B. 

 B. 

 M. I. 



— B. M. 



M. 



