3 iS DISCOVERY REPORTS 



around the cell wall and in lines which radiate from the nucleus. Diameter of cell 

 ioo-200/x ; pervalvar axis up to i mm. 



An oceanic species, widespread in tropical and subtropical waters, frequent in the 

 Mediterranean, but seldom in the northern waters of Europe and the North Atlantic. 

 It was observed but seldom in great numbers, around the Cape of Good Hope on the 

 eastern side, off the coast of Natal, and on the east coast of Africa, off Madagascar to 

 the south-west and again north of that island off the coast of Kenya and Somaliland. 



Observed at Sts. 425, 428, 433, 435, 440, 1572, 1575, 1584, 1586; WS 700, 701, 703, 

 704, 706, 709. • 



Rhizosolenia setigera Brightwell. 



Brightwell, 1858, p. 95, pi. 5, fig. 7. 



Hustedt, 1929, p. 588, fig. 336. 



Lebour, 1930, p. 98, fig. 70. 



Rhizosolenia J aponica Castracane, 1886, p. 72, pi. 23, fig. 7. 



Rhizosolenia Hensenii Schiitt, 1900, p. 510, pi. 12, figs. 25-27. 



Cells cylindrical, tubular, straight, usually solitary. Valves deeply conical, regular, 

 furnished with a very long terminal spine. Spine straight, or only very slightly bent. 

 Connective zone composed of two pervalvar lines of intercalary plates. Imbricate 

 markings seen with difficulty, having the appearance of a zigzag line in lateral aspect. 

 Chromatophores : numerous cocciform bodies. Diameter of cell 10-20/x; length of 

 spine 60-120 ix. 



A neritic species, which favours cold waters. It is common around the coasts of most 

 European countries, particularly those with an Atlantic seaboard. It was observed in 

 small quantities at one station only in the Atlantic Ocean in latitude 20° S on the 30th 

 W meridian. 



Observed at St. 681. 



Rhizosolenia Shrubsolii Cleve. 



Cleve, 1881, p. 26. 

 Gran, 1905, p. 52, fig. 63. 

 Lebour, 1930, p. 96, fig. 69. 



Cells cylindrical, slightly flattened laterally, usually solitary, but sometimes united 

 to form short chains. Valves shortly conical, strongly eccentric, oblique, but curved on 

 the ventral side and furnished with a short spine in line with the dorsal margin of the 

 cell. Spine hollow throughout almost all its length and furnished with an alate base. 

 The valve often bears a small depression which corresponds to the spine of the neigh- 

 bouring cell. Connective zone composed of two pervalvar lines of intercalary scale-like 

 markings transapically opposed. The imbrications have the appearance of a zigzag line 

 when the cell presents the ventral aspect. The cell is covered with a fine striation, which 

 is usually finer on the valve than on the connective zone and is often very weakly 

 siliceous. Chromatophores: numerous cocciform bodies arranged around the cell wall 

 and in lines radiating from the central nucleus. Diameter of cell 20-44^. 



