SYSTEMATIC ACCOUNT 311 



A neritic species, but also found under oceanic conditions. Very widespread, often 

 associated with the type, but more common in subtropical waters. A very weakly 

 siliceous species. It was common around the Cape of Good Hope, particularly on the 

 east side, extending northwards of Madagascar along the Somaliland coast, often in 

 great numbers. It was common also under sub-Antarctic conditions off Bouvet Island 

 and in the Weddell Sea in summer, also around South Georgia and between the Falkland 

 Islands and Port Desire on the mainland of South America. 



Observed at Sts. 294, 335, 427, 428, 431, 432, 437, 440, 461, 477, 542-4, 552, 553, 

 574-576, 578, 580, 666, 671, 675, 1376, 1584, 1586; WS 100, 101, 106, 107, 469, 474, 

 481, 600, 629, 630, 631, 666, 710, 714, 715. 



"indica" phase. 



Rhizosolenia alata, forma indica (Peragallo) Hustedt. 



Ostenfeld, 1901, p. 160 (as var.). 



Hustedt, 1929, p. 602, fig. 346. 



Rhizosolenia indica Peragallo, 1892, p. 116. 



Rhizosolenia alata, var. indica (Peragallo) Ostenfeld et Schmidt. 



Cells structurally similar to the type, but possessing a much greater diameter. Valve 

 broadly conical, narrowing suddenly to produce the short and relatively thin process. 

 Process more centric than that of the type, but often set in an oblique position. The 

 markings upon the connective zone may be composed of two rows of dorsiventral, 

 scale-like bands or numerous imbricated scales. Scales striate. Diameter of cell 

 20-60 /x. 



An oceanic species, more common in tropical and subtropical waters than in cold 

 water. It was observed at two stations only in the Peru Current. 



Observed at Sts. WS 705, 706. 



"inermis" phase. 



Rhizosolenia alata, forma inermis (Castracane) Hustedt. 

 Hustedt, 1929, p. 602, fig. 348 



Rhizosolenia inermis Castracane, 1886, p. 71, pi. 24, figs. 7, 8, 10. 

 Rhizosolenia obtusa Hensen, 1887, p. 86, pi. 5, fig. 41. 



Cells structurally similar to the type, but possessing valves with sharply truncated 

 apices. Apices straight or only very slightly curved, and bearing a small but distinct 

 cleft. Diameter of cell 10-20/x. 



An oceanic species having a wide distribution in all northern waters. It was observed 

 frequently around the coast of Africa, Cape Horn, South Georgia, and far south in the 

 Weddell Sea. 



Observed at Sts. 260, 262, 381, 383, 384', 440, 460, 475, 478, 480, 482, 501, 508-510, 



5 I2 > 5*3. ^58, 1359; ws 545> 548, 55°-55 2A - 

 Rhizosolenia annulata Karsten. 

 Karsten, 1907, p. 378, pi. 41, fig. 4. 

 Cells large, usually solitary, straight. Valves shortly conical, very oblique, ventral side 



