3 o6 DISCOVERY REPORTS 



Suborder SOLENIINEAE 



Family BACTERIASTRACEAE 



Subfamily BACTERIASTROIDEAE 



i. Cells cylindrical, united in chains, each valve possessing usually four bristles, which, in the 

 middle of the chain bifurcate, terminal bristles simple Bacteriastrum 



Genus Bacteriastrum Shadbolt 

 Shadbolt, 1854 



Bacteriastrum comosum Pavillard. 



Pavillard, 1916, p. 29, pi. 1, fig. 3. 

 Hustedt, 1930, p. 622, fig. 361. 



Cells united to form chains, six to fourteen cells in a chain. Cells elongated, cylin- 

 drical. Valve mantle deep, connective zone seldom as deep as the valve mantle. Valve 

 surface furnished with a circlet of usually eight pendulous bristles which emerge at the 

 margin of the valve almost in the axis of the chain and turn outwards obliquely and fuse 

 with the bristles of the neighbouring cells. The fused portion proceeds at right angles to 

 the axis of the chain for approximately one-third of the total length of the bristle and 

 then bifurcates. The bifurcate ends are bent towards the posterior end of the chain and 

 are slightly recurved. Foramina distinct. The bristles on the upper valve of the terminal 

 cell at the anterior end of the chain are thick, and are not bifurcate ; they are slightly 

 pendulous and somewhat tortuous. The bristles on the lower valve of the terminal cell 

 at the posterior end of the chain are thicker and longer than the others. They emerge 

 at right angles to the axis of the chain in a direction parallel with the chain axis. These 

 posterior bristles are somewhat tortuous, undulate, and bear spiral markings. The valve 

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

 close to the bristles. Valves hyaline. Chromatophores : several plate-like bodies. 

 Diameter of valve 15-24/x ; pervalvar axis 46/^. 



This species has a localized tropical distribution. It has been reported from the 

 Mediterranean, but is not frequent there. It was observed in considerable quantity off 

 the east coast of Africa in equatorial waters, and favours a high salinity ; it is probably 

 a neritic species. 



Observed at Sts. 1583, 1584, 1586. 



Bacteriastrum criophilum Karsten. 

 Karsten, 1906, p. 170, pi. 33, fig. 22. 

 Cells united to form chains, four to eight cells in a chain. Cells elongated, cylindrical. 

 Valve mantle very deep. Valve surface furnished with a circlet of usually six pendulous 

 bristles. The bristles emerge slightly obliquely and at about one-third the total length 

 bend towards the posterior end of the chain becoming almost parallel with the chain 



