336 DISCOVERY REPORTS 



Cells linear, very long, often bent in the form of an S. Valves with parallel sides and 

 rounded apices. Striations upon the valve margins very fine. Chromatophores : 

 numerous rounded bodies. Apical axis of cell 1-3 mm. 



This form has a wide distribution in the South Atlantic, Pacific and Indian Oceans. 

 It has been reported by Skvortzow from the China Seas. It was observed often in con- 

 siderable quantity in the Peru Current material. 



Observed at Sts. WS 598, 600, 601, 602. 



Thalassiothrix longissima Cleve et Grunow. 



Cleve and Grunow, 1880, p. 108. 

 Karsten, 1905, p. 124. 

 Lebour, 1930, p. 198, fig. 159. 



Cells solitary, often found in large tangled masses. Cells very long and thin, often 

 slightly curved. Poles of the cells tapering very slightly, one usually more than the 

 other, and each bearing two small apiculi. Valves minutely striate, bearing numerous 

 marginal apiculi, apices bluntly rounded. Chromatophores: numerous cocciform 

 bodies. Apical axis of cells up to 3-4 mm. 



This species is widely distributed throughout the colder waters of both north and 

 south hemispheres. It was observed, sometimes in enormous quantities, around South 

 Africa, and particularly in that part of the Southern Ocean which lies to the south of 

 that continent, between it and Enderby Land. 



Observed at Sts. 424, 427, 428, 436, 439, 440, 450, 460, 670, 1356, 1358, 1359 ; WS 598. 



Genus Thalassionema Grunow ex Hustedt 



Hustedt, 1932 



[Grunow ex Van Heurck, 1881-85] 



The genus Thalassionema has often been attributed to Grunow because of the ex- 

 planatory note made by him upon pi. 43 of Van Heurck's Synopsis (1881-85) under 

 Thalassiothrix nitzschioides Grun., which was as follows: "On pourrait peut-etre en 

 creer un nouveau genre nomme Thalassionema." 



Owing to the vague mention of the proposed new genus, and the fact that no specific 

 epithet was used in combination, Grunow's publication of this name must be ruled as 

 invalid. The authority is attributed to Hustedt who gave a full generic description, 

 followed by a description of Thalassionema nitzschioides. 



Thalassionema nitzschioides Hustedt. 

 Hustedt, 1932, p. 244, fig. 725. 



Cells united to form stellate or zigzag colonies. Valves linear, with parallel sides and 

 bluntly rounded apices. Valve surface structureless, but the margins are furnished with 

 minute spinulae. Connective zone simple, having a rectangular aspect. Chromato- 

 phores: numerous cocciform bodies. Apical axis of cell 30-90/i, transapical axis 2-5/M. 



A very common pelagic diatom, frequently observed around the coasts of European 



