PLAXKTOX-TYI'ES. STYLIl'I.ANKTOX. DIDYMU.S-l'LAXKTOX. 19 



Mean Outside 



Limits '<="'P- •'!'"" '^'^ 



rature salimty Atlantic 



Chii'toeeros volans 4°S.— VT^'N. 14.i 35.09 



Gorethron hystrix 7°N.— 76°N. 10.4 35.i2 North \\ 



CoscinodiscLis sol 82°S.— 57°N. 15.5 ^b.Hi> M. U. P. 



Dactyliosolon antarcticus 35°N.— 62°N. 11. 7 35.87 Antarclic. 



D. hyalinus 32°N.— 47°N. 14.4 35.oo 



Hemidiscus cimeiformis... 29°S.— 66°N. 20..-! 35.o.; M. 1. 



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



Rhizosolenia alata 30^S.— 66°N. 11. 9 35..i.. M. I. P. 



R. corpulenta 5°S.— 64°N. 15.7 35.36 North P. 



R. styliformis 26"S.— 80"N. 12.o 34.7i, M. P. 



Jt 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. 



Limits 



Podon intermedins 40°N.— 70°N. 



Acartia bifilosa 6° S.— 63°N. 



Euterpe acutifrons 40°S.— 51°N. 



Cyttarocylis serrata 33° S.— 58°N. 



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



Bacteriastrum varians ... 7''N. — 58° N. 



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



Cerataulina Bergonii 7-N.— 80°N. 



14.4 



11.3 



34.94 

 34.88 



B. M. 



M. 



