24 



PLANKTON-TYPES. TROPICAL NERITIC PLANKTON. 



The temperature of the water that contains Desmo-plankton is 

 high, above 20°, and the salinity 36 p. m. or more. 



The coast regions of the tropical Atlantic are characterized by 

 a number of more or less brackish species, of which I give the 

 following list: 



Tropical neritic plankton. Nt. 



Limits 



Temora styHfera 37° S.— 42°N. 



T. turbinata 6° S.— 18°N. 



Asterionella notata 18°N.— 40°N. 



Biddulphia chinensis 7°N.— 10°N. 



Chsetoceros (didym. v.) 



longicruris 29° S.— 49. N. 



C. diversus 29°S.— 40°N. 



C. femur 7°N.— 12°N. 



Coscinodiscus nobilis 5° S — 6° S. 



Ditylum sol 10°N. 



Nitzschia pungens 7°N. — 10° N. 



Rhizosolenia cylindrus ... 3°N.— 42°N. 



R. robusta 5°S.— 50°N. 



Skeletonema tropicum ... 29° S.— 10°N. 



I call the kind of plankton constituted by these species Tropical 

 neritic planktun (Sign. Nt.) Some of the species falling under 

 that kind have a very wide range of distribution, i. e. have been 

 found off Australia, in the Malay Archipelago elc. 



