SYSTEMATIC ACCOUNT 33 i 



in a horse-shoe fashion. Valves linear-lanceolate in outline, valve surface slightly inflated, 

 and furnished with numerous transverse lines, connective zone simple. Chromato- 

 phores : numerous cocciform bodies, nucleus somewhat large, central. Apical axis of 

 cell 40-56/u. 



Probably neritic, common in the warmer waters around South Africa. 



Observed at Sts. 260, 261, 262, 263, 264, 431, 432, 434; WS 630, 631, 706, 707. 



Fragilaria linearis Castracane. 



Castracane, 1886, p. 56, pi. 19, fig. 9. 



Heiden and Kolbe, 1928, p. 550, pi. 6, fig. 128. 



Cells linear, united to form flat ribbon-like chains. Valves flat, with apices rounded, 

 and lateral margins straight. Valve surface furnished with numerous fine transverse 

 striae. Connective zone well developed, simple. Chromatophores : several small plates 

 adhering to the valves. Apical axis of cell 50/x ; transapical axis 6-8^. Type locality, 

 Antarctic Ocean. 



Castracane pointed out that in the perfectly linear outline of the valve this organism 

 differed from any previously recorded species of this genus. 



The species was observed in water obtained from melted ice. 



Observed near St. 560. 



Fragilaria striatula Lyngbye. 



Lyngbye, 1819, p. 183, pi. 63. 

 Gran, 1905, p. 113. 



Cells united to form chains, seldom solitary. Valves narrowly lanceolate, with apices 

 somewhat attenuate. Valve with narrow median pseudoraphe. Valve surface covered 

 with delicate transverse striae. Connective zone composed of numerous plicae. Apical 

 axis of cell 30/i ; transapical axis 5/i. 



A weakly siliceous, marine Fragilaria, usually associated with a coastal flora, but often 

 found in the plankton. It has been recorded from the Atlantic coasts of most European 

 countries. It was observed, but in a small quantity only, around South Georgia, and at 

 two stations in mid-Atlantic on the 30th W meridian. 



Observed at Sts. 475, 671, 677. 



Genus Fragilariopsis Hustedt 

 Hustedt, in Schmidt, 1913 



The genus Fragilariopsis was created by Hustedt (Hustedt, in Schmidt, 1913, pi. 

 299), to accommodate Fragilaria antarctica Castracane (Castracane, 1886, p. 56). The 

 division was well-founded, for the type-species of Hustedt's genus differed in structure 

 from Fragilaria in more than one respect. The valve surface of Fragilariopsis antarctica 

 possesses no median hyaline area or pseudoraphe in the apical axis of the cell, which is 

 a constant character in the genus Fragilaria. In Fragilariopsis the markings are un- 

 interrupted, and consist of transverse lines of puncta alternating with hyaline folds or 

 ridges. 



