22 r. T. CLEVK, NOTES UN SURIE ATLANTIC I'LANKTON-OHGANISMS. 



Skeletouema tropicuni. N. Sp. 

 riate VIII. Fig. 30, 31. 



This species differs from S. costatiim in its larger size and numerous, closer peri- 

 pherical processes. Sagittal axis 0,oi5 to 0,o38, longitudinal axis 0,oi millini. Processes 

 7 to 9 in 0,01 millim., their length 0,oi to 0,o2 millim. 1 found this species in samples 

 from the coasts of S. America, 29 S. and 6 10N. Temperature 23,8 to 27,2. Salinity 

 from 34,53 to 36,oi. Evidently a tropical neritic form. 



Thalasslosira condensata. N. Sp. 

 riatc VIII. Fig. 12, 13. 



Cellules very thin-walled, short, cylindrical, united by a single central short slim- 

 thread to somewhat rigid chains. Valve orbicular with a central pore and a marginal 

 circlet of close small protuberances, about 7 in 0,oi millim., but else without any visible 

 structure (on ignited specimens). Zone with numerous rings. Chromatophores small and 

 rounded, along tho interior wall of the cellule. Length 0,02 to 0,03, diameter 0,o25 to 0,03 

 millim. 



The membrane is so little silicious that it, on drying, becomes deformed. 



This species was found in October 1899 at Plymouth together with several arctic 

 forms. 



