SYSTEMATIC ACCOUNT 295 



separate diverging appendages, and are not fused together to make the surface of the 

 upper valve flat, as in Chaetoceros criophilum Castracane. Chromatophores : several 

 small bodies. Diameter of valve in the polar axis 15-36/x ; pervalvar axis of cell 10-15^. 



This species was observed occasionally around the coasts of South Africa. 



Observed at Sts. 425, 427, 440. 



Chaetoceros pendulum Karsten. 

 Karsten, 1905, p. 118, pi. 15, fig. 7. 



Cells solitary, sometimes three or four are matted together but not united to form 

 chains. Valves elliptical in outline. Valve surface concave, that of the upper valve more 

 so than the lower. Bristles emerging just inside the girdle line. The bristles of both 

 valves proceed in the same direction, obliquely at first, then curving almost parallel 

 with each other and with the pervalvar axis of the cell. Bristles long, pendulous, smooth. 

 Chromatophores : numerous small cocciform bodies penetrating the bristles. Diameter 

 of valve 18-28/^. 



A neritic form common in the South Atlantic Ocean. It was observed between the 

 South Shetlands and Cape Horn, but never in great numbers. 



Observed at Sts. 378, 379, 380, 382, 383, 384, 451. 



Chaetoceros Castracanei Karsten. 

 Karsten, 1905, p. 116, pi. 15, fig. 1. 



Cells united to form chains, six to twenty cells in a chain, cells rectangular in girdle 

 view. Valve elliptical in outline, central area slightly inflated. Angles of valve produced 

 to form stout, stiff bristles, which proceed in straight lines at right angles to the axis of 

 the chain. The bristles are armed with small spines throughout the greater part of their 

 length, but are smooth near the point of emergence. The valves of one cell almost touch 

 those of the neighbouring cells ; the foramina therefore are much reduced, almost absent. 

 Valve mantle deep, gently constricted as it meets the connective zone. Girdle rather 

 narrow. Chromatophores: numerous small oval bodies, penetrating the bristles. 

 Diameter of valve 20-25^. 



A neritic species, observed in great numbers off Cape Horn, very common in the 

 Antarctic. 



Observed at Sts. 378, 379, 380, 382, 383. 



Chaetoceros criophilum Castracane. (PI. XIII, fig. 7.) 



Castracane, 1886, p. 78. 



Karsten, 1905, p. 118, pl. 15, fig. 8. 



Mangin, 1915, p. 34, figs. 13, 14. 



Cells united to form short chains, but often solitary. Valves dissimilar. Valve surface 

 almost circular, the upper strongly convex, with deep valve mantle, the lower almost 

 flat, with narrow valve mantle. Bristles very long, with sweeping curves. The bristles 

 of the upper valve emerge from the centre as part of the valve surface, while those of the 

 lower valve emerge from a point nearer the valve margin. Bristles armed with small 



D XVI 19 



