3i2 DISCOVERY REPORTS 



gently curved. Valve terminated with a short sharp spine, hollow at the base. Spine not 

 erect, but directed outwards over the dorsal margin of the cell. Connective zone com- 

 posed of numerous regular annular segments arranged in two dorsiventral lines, edges 

 of segments parallel. Imbrications clear, undulated close to the valve margin. The cell 

 wall is covered with a very fine punctation, arranged in quincunx. Chromatophores : 

 numerous rather large rounded bodies. Diameter of cell 90-1 io/t. 



A large tropical species, probably oceanic. It was observed in small numbers off the 

 Brazil coast. 



Observed at Sts. 719, 721, 722. 



Rhizosolenia Bergonii H. Peragallo. 



Peragallo H., 1892, vol. I, p. no, pi. 3, fig. 5 (pi. 15, fig. 5). 



Gran, 1905, p. 51, fig. 60. 



Hustedt, 1929, p. 575, fig. 327. 



Lebour, 1930, p. 102, fig. 746. 



Rhizosolenia ampatata Ostenfeld, 1902, p. 227, fig. 4. 



Cells cylindrical, straight, furnished with long conical valves. Valves produced, 

 slightly attenuate, terminated with a short, straight spine. Spine truncate, bearing a 

 small central canal. This canal is slightly inflated at its base, and cup-shaped at the apex 

 of the spine. The connective zone is furnished with four or five rows of scale-like inter- 

 calary bands. The dorsal margin of the scales is curved, or bow-shaped. The whole cell 

 is minutely punctate, but the valves are a little more strongly marked than the con- 

 nective zone. Chromatophores: numerous cocciform bodies. Diameter of cells 

 80-100/x ; pervalvar axis 550^. 



An oceanic species having a wide distribution in tropical and subtropical seas. It was 

 observed in the equatorial regions of the Atlantic Ocean, off the west coast of Africa. 



Observed at Sts. 293, 675, 684, 687. 



Rhizosolenia bidens Karsten. 



Karsten, 1905, p. 98, pi. 9, fig. 13. 



Cells cylindrical, usually solitary. Valves regularly conical, terminated with a large 

 bifurcate spine. Connective zone composed of two dorsiventral lines of intercalary scale- 

 like markings, somewhat similar to those of R. styliformis. Chromatophores: numerous 

 cocciform bodies. Diameter of cell 40-80/*. 



The illustration provided by Karsten gives little idea of the size and strength of the 

 bifurcate spine so characteristic of this species. It is more adequately illustrated by 

 Castracane (1886) pi. 24, fig. 14, as Rhizosolenia sp. 



An oceanic and cold-water species. It was common around South Georgia, the South 

 Shetlands and the South Sandwich Group. 



Observed at Sts. 368, 369, 378-381, 383, 425, 475, 479, 507; WS 542, 543. 



Rhizosolenia calcar-avis Schultze. (PI. XI, fig. 14.) 



Schultze, 1858, p. 339, pl. 13, figs. 5-8. 

 Karsten, 1907, p. 380, pl. 41, fig. 5. 



