304 DISCOVERY REPORTS 



Section Brevicatenata 



Chaetoceros fragile Meunier. 



Meunier, 1910, p. 244, p. 27, figs. 27-29. 

 Lebour, 1930, p. 153, fig. 116. 



Cells small, united in short irregular chains ; usually four to eight cells in a chain, 

 sometimes solitary. Cells in girdle view rectangular, valves slightly convex, oval in out- 

 line. Bristles arising directly from the corners of the cell. Bristles thin and usually short, 

 often crossing those of the neighbouring cell outside the girdle line of the cells. Bristles 

 of the two valves proceeding in opposite directions. Chromatophores : few cocciform 

 bodies. Diameter of valve 8-12/* ; pervalvar axis 8-10/x. 



This very small species was met with but once. It occurred in small numbers off the 

 coast of Natal. It was described first by Meunier from the Arctic. 



Observed at St. 440. 



Chaetoceros pseudocrinitum Ostenfeld. 



Ostenfeld, 1901, p. 300, fig. 11. 

 Hustedt, 1930, p. 733, fig. 422. 

 Lebour, 1930, p. 154, fig. 118. 

 Cells united to form straight chains, in girdle view rectangular. Valves elliptical in 

 outline, with flat central areas. Angles of the valves very slightly produced. The bristles 

 are slightly divergent ; they emerge from the poles of the cells and cross those of the 

 neighbouring cell at the point of emergence and proceed at right angles to the axis of 

 the chain. The bristles upon the lower valve of a terminal cell emerge and continue 

 obliquely for about one-third of their length, and then turn gently in a direction almost 

 parallel with the axis of the chain. Foramina linear-lanceolate. Chromatophore : one 

 large plate. 



A neritic species, widely spread throughout northern waters. It was observed at one 

 station off South Africa, in small numbers only. 

 Observed at St. 432. 



Section Diversa 



Chaetoceros messanense Castracane. 



Castracane, 1875, p. 394, fig. 1. 

 Hustedt, 1930, p. 718, fig. 410. 

 Chaetoceros furca Cleve, 1897, p. 21. 



Cells usually united to form short chains. Valves elliptical in outline ; central area flat, 

 poles produced to form stiff bristles, which cross with those of the neighbouring cells 

 at the point of emergence. Valve mantle narrow, connective zone often deep. Three 

 distinct types of bristles may be observed in the one chain. The majority of the bristles 

 are thin and relatively short, but occasionally there occurs a pair of very stout, straight 

 bristles, with widely bifurcate ends. The apices of the bifurcate extensions often show 

 spiral markings, but these may be absent. The bristles upon the lower valve of a ter- 



