3 2o DISCOVERY REPORTS 



Rhizosolenia styliformis Brightwell. (PI. XI, figs. 15-17.) 



Brightwell, 1858, p. 95, pi. 5, fig. 5. 

 Karsten, 1905, p. 96, pi. 10, fig. 5. 

 Hustedt, 1928, p. 584, fig. 333. 

 Heiden et Kolbe, 1928, p. 516. 

 Lebour, 1930, p. 98, fig. 71. 



Cells cylindrical, straight, solitary. Valves rather deeply conical, oblique, ventral 

 margin almost straight, furnished with an apical spine, which is arranged in a straight 

 line with the dorsal margin of the valve. The spine is furnished with a cavity which 

 penetrates the valve, and wing-like projections at the base. The valve bears a depression 

 which corresponds to the spine of the sister cell. Connective zone composed of two 

 dorsiventral lines of intercalary scale-like markings which have the appearance of inter- 

 locking fingers when the cell presents a lateral aspect, and not a zigzag of straight lines 

 as in the ventral aspect of R. Shrubsolii. Cell wall usually strongly siliceous and im- 

 brications clear. Connective zone covered with a fine punctation arranged in quincunx. 

 Chromatophores : numerous cocciform bodies, arranged around the cell wall and in 

 lines radiating from the central nucleus. Diameter of cells 40 -100/x. 



An oceanic species, widely spread throughout all parts of the globe, perhaps the most 

 common species of Rhizosolenia. It was observed frequently and sometimes in con- 

 siderable quantities around the coast of South Africa, particularly on the east side and 

 northwards by Madagascar and the Somaliland coast, under tropical conditions. It was 

 very common around South Georgia, the South Sandwich Group, Bouvet Island, and 

 in the Drake Strait, under sub-Antarctic conditions. It was not observed, however, far 

 south in the Bellingshausen or Weddell Seas. 



Observed at Sts. 334-339, 385-388, 427, 431, 432, 433, 438, 461, 475, 477-479- 4 8 2, 

 512, 661, 663, 681, 1356, 1358, 1359, 1373, 1570, 1572, 1574. 1581, 1584- 1586, 1589; 

 WS 100, 104, 469, 474, 551, 569, 601, 645, 700, 701, 703, 704, 709, 710, 711 ; MS 86; 

 RS9. 



Rhizosolenia truncata Karsten. 



Karsten, 1905, p. 97, pi. 10, fig. 3 a. 

 Van Heurck, 1909, p. 28, pi. 4, fig. 73. 



Cells small, cylindrical, united to form short chains, but sometimes solitary. The 

 valves may be dissimilar, the one shortly conical, with its apex in an oblique position, 

 the other shortly conical, with its apex drawn out to form a long slender erect process. 

 Spines absent. The exterior valves of the terminal cells produce the long slender process. 

 The cells are very weakly siliceous and the imbrications upon the connective zone are 

 seen with great difficulty. Chromatophores : numerous cocciform bodies ; nucleus small, 

 usually eccentric. Diameter of cells 10-14/x ; pervalvar axis 120/u. 



An oceanic species, probably truly Antarctic. It was observed in small numbers only 

 in the Bellingshausen Sea. 



Observed at Sts. 461, 580. 



