314 DISCOVERY REPORTS 



finely striate. Chromatophores : numerous cocciform bodies. Diameter of cell 26-32/i ; 

 pervalvar axis 80/x. 



A characteristic Antarctic species. It was observed in small numbers at most stations 

 in the Bellingshausen Sea and off Cape Horn. 



Observed at Sts. 574, 575, 577, 578, 580; WS 593, 594. 



Rhizosolenia crassa Schimper ex Karsten. 

 Karsten, 1905, p. 99, pi. 11, fig. 6. 



Cells large, often united to form short chains, cylindrical, but often flattened laterally. 

 Valves shortly conical, slightly oblique, terminated by a long eccentric spine. Spine 

 bulbous and hollow at the base, tapering to a fine point. Connective zone composed of 

 usually two dorsiventral lines of intercalary scale-like markings. Imbrications clear, 

 wavy, sometimes squamose. Chromatophores : numerous cocciform bodies, often con- 

 glomerated to form a transapical band through the cell, surrounding the nucleus. 

 Diameter of cell 160-220/^ ; pervalvar axis 400-900^. 



Probably a neritic species. Typically Antarctic. It was observed sometimes in quan- 

 tities around South Georgia, the South Sandwich Group and Bouvet Island. 



Observed at Sts. 334, 335, 337-440, 461 ; WS 469, 542. 



Rhizosolenia curvata Zacharias. 



Zacharias, 1905, p. 121 



Rhizosolenia curva Karsten, 1905, p. 97, pi. 11, fig. 2. 



Cells cylindrical usually solitary, but may be in short chains, slightly curved, some- 

 times crescentic. Valves deeply conical, regular, terminated with a long sharp spine. 

 Spine slender, with hollow base. Connective zone composed of two lines of dorsi- 

 ventral intercalary scale-like markings, similar to R. styliformis. Cells weakly siliceous, 

 imbrications seen only with difficulty. Scales furnished with very fine punctation 

 arranged in quincunx. Chromatophores: numerous cocciform bodies, often arranged 

 around the cell wall, nucleus usually central. Diameter of cells 20-60/j. 



A typical sub-Antarctic species widely spread throughout the Southern Ocean, often 

 in great numbers. It was observed frequently around South Georgia and in the Drake 

 Straits. It was observed also to the south-east of the Cape of Good Hope, in the latitude 

 of 42 S on the 40th E meridian. 



Karsten 's Rhizosolenia curva was published in 1905, in the same year as Zacharias 's 

 name Rhizosolenia curvata, and it was a matter of great difficulty to establish the claim 

 of the latter to priority. Hart (1935, p. 160) used Karsten's combination to describe this 

 species, but during a critical study of the literature later, discovered that Zacharias 's 

 publication appeared first, and that Karsten admitted Zacharias's claim and adopted his 

 name in 1907 (Deutschen Tiefsee Exped. 1907, p. 164). I am indebted to Dr Hart for 

 furnishing me with these particulars. 



Observed at Sts. 387, 388, 433, 501, 659, 666, 670, 671, 679, 1369. 



