SYSTEMATIC ACCOUNT 307 



axis. The bristles do not furcate and are armed with small spines throughout the greater 

 part of their length. The bristles of the terminal cells differ but slightly; those of the 

 lower valve at the posterior end of the chain are longer and more pendulous, that is, they 

 proceed in the direction of the chain axis for almost their entire length. The valve 

 mantles of the anterior and posterior valves of terminal cells are sharply constricted 

 close to the bristles. Foramina small, difficult to define. Chromatophores : numerous 

 cocciform bodies. Diameter of valve 14-18/x ; pervalvar axis 40-60/i. 



A very common species around the coast of South Africa. 



Observed at Sts. 435, 437, 438, 439. 



Bacteriastrum elongatum Cleve. 



Cleve, 1897 a, p. 19, pi. 1, fig. 19. 

 Karsten, 1905, p. 170, pi. 33, fig. 23. 

 Ikari, 1927, p. 425, fig. 5 a. 

 Hustedt, 1930, p. 617, fig. 357. 

 Lebour, 1930, p. 85, pi. 3, fig. 2 a. 



Cells united to form chains. Cells elongated, cylindrical. Valve mantle deep, con- 

 nective zone usually the same depth as the valve mantle. Valve surface furnished with 

 seven to nine bristles, emerging obliquely and fusing, for a very short distance only, 

 with the bristles of the neighbouring cells. The bristles then bifurcate and are arranged 

 almost in the plane parallel with the chain axis. Bristles rather short and straight. 

 Bristles of terminal cell alike at both ends of the chain. The terminal bristles are thicker; 

 they emerge from the valves slightly obliquely, and curve gently towards the chain 

 axis, until parallel with it. The bristles of the terminal cells point in opposite directions 

 and are furnished with small spiral markings. Foramina small, somewhat indistinct. 

 Chromatophores: several small rounded bodies. Diameter of valve 12-24/^ ; pervalvar 

 axis up to 60/x. 



This species was widely spread through temperate and subtropical seas. It was ob- 

 served very frequently around the coast of South Africa sometimes in great numbers. 



Observed at Sts. 425, 427, 428, 432, 434, 435, 436, 437, 438, 439, 440. 



Bacteriastrum delicatulum Cleve. 



Cleve, 1897 b, p. 298, fig. 15. 

 Gran, 1905, p. 58, fig. 72. 

 Hustedt, 1930, p. 612, fig. 353. 

 Ikari, 1927, p. 424. 



Cells united to form straight chains. Cells elongated, cylindrical. Each valve fur- 

 nished with a circlet of seven to ten bristles which emerge obliquely and fuse with those 

 of the neighbouring cells. The fused portion, equal to about half the total length of the 

 bristle, proceeds outwards at right angles to the chain axis, and then bifurcates. The 

 bifurcate portions are bent only very slightly. The bristles attached to the exterior valves 

 of the terminal cells are thicker than the others ; they are alike at both ends of the chain 

 and bent back towards the chain axis, somewhat irregularly, and armed with very small 



