SYSTEMATIC ACCOUNT 291 



Bristles proceeding from valve surface in the manner of the type, but continuing for a 

 short distance almost parallel with the pervalvar axis before turning outwards to cross 

 the bristles of the neighbouring cells. Bristles sometimes slightly curved back. Fora- 

 mina varying considerably, often oblong in shape with the long axis in the pervalvar 

 plane, but sometimes diamond-shaped. Chromatophores : numerous cocciform bodies, 

 penetrating the bristles. Diameter of valve 8-12/j. ; pervalvar axis up to 20^. 



A small oceanic form, preferring temperate and subtropical water. It was observed 

 frequently around the coast of Africa, sometimes mixed with the type. 



Observed at Sts. 368, 427, 428, 435, 439, 1373, 1586; WS 550. 



Chaetoceros dichaeta Ehrenberg. (PI. VI, figs. 9, 10.) 



Ehrenberg, 1844, p. 200. 



Gran, 1905, p. 66, fig. 77. 



Mangin, 1915, p. 37, figs. 17-26. 



Van Heurck, 1909, pi. 5, figs. 78-82. 



Hustedt, 1930, p. 648, fig. 367. 



Chaetoceros remotus Cleve et Grunow, 1880, p. 120. 



Chaetoceros Janischianum Castracane, 1886, p. 77. 

 Cells united to form chains. Chains straight and stiff. Valves elliptical to circular, 

 convex, bearing a sharp central spine. Valve mantle narrow. Bristles emanating from 

 well inside the valve margin and proceeding upwards in a direction parallel with the 

 pervalvar axis for a considerable distance to meet the bristles of the next cell. At the 

 point of contact the bristles turn outwards parallel with the apical plane of the valve. 

 The bristles on the lower valve of a terminal cell emerge somewhat obliquely at first, but 

 later are bent towards the chain axis. Girdle very narrow, indistinct. Foramina varying 

 considerably; in some specimens they appear to be almost diamond shape, while in 

 others almost hexagonal, usually large. Lengths of connective tissue are frequently 

 observed between the cells. Chromatophores: numerous small plates or cocciform 

 bodies, penetrating the bristles. Diameter of valve 20-50/i. 



An oceanic species, having a wide distribution in the southern hemisphere. It was 

 observed very frequently around the coast of South Africa, South Georgia and along the 

 east coast of Africa. Very common throughout the Southern Ocean, but not in the 

 extreme south. 



Observed at Sts. 365, 368, 369, 378-386, 425, 427, 428, 433, 452, 453, 460, 461, 463, 



5 6 °. 574- 577. 5 8 °- 666 > l ZS^ ^S 8 * T .W 

 Chaetoceros cruciatum Karsten. 

 Karsten, 1905, p. 116, pi. 15, fig. 5. 

 Cells united to form short chains, usually four to eight cells in a chain; sometimes 

 solitary. Cells rectangular in girdle view. Valves elliptical, valve surface with slight 

 medium inflation, surmounted by a sharp spine. Bristles emerging well inside the girdle, 

 almost half way between the girdle and the median spine, and proceeding outwards 

 obliquely. Strongly divergent, diagonal, alternate and opposite bristles of each cell in 

 the chain cross the corresponding bristles of the neighbouring cells at an angle of about 



