SYSTEMATIC ACCOUNT 243 



Karsten, 1905, p. 80, pi. 8, fig. 2. 



Lebour, 1930, p. 37, fig. 14. 



Gran, 1905, p. 30, fig. 30. 



Coscinodiscus Ehrenbergii O'Meara, 1875-77, P- 2 ^ P'- a6 > %• 2 4- 



Coscinodiscus leptopus Grunow ex Van Heurck, 1880-5, P^ I 3 I > %• 5- 



Cells discoid, solitary, strong. Valves usually flat but sometimes weakly convex. 

 Valves covered with polygonal areolation arranged in tangential lines based upon six 

 sectors. Areolae slightly smaller at the margin than in the central area of the valve. 

 Margin strong, sometimes broad, radially striate, furnished upon the inner edge with a 

 row of stout spinulae. Chromatophores ; numerous plate-like bodies. Diameter of 

 valve 44-120/i.. 



This species has a world-wide distribution in temperate and subtropical seas, and 

 although a truly neritic diatom, is observed sometimes in oceanic plankton. The valves 

 show much variation in diameter and coarseness of areolation. Species from cold 

 waters are usually considerably smaller than those from warm seas. 



Observed at Sts. 263, 264, 340, 368, 369, 379, 380, 381, 382, 383, 384, 388, 440, 450, 

 659, 666, 1373, 1575. 



STELLATAE Rattray 

 Coscinodiscus stellaris Roper. 



Roper, 1858, vol. vi, p. 21, pi. 3, fig. 3. 



Gran, 1905, p. 37, fig. 40. 



Karsten, 1905, p. 84, pi. 4, fig. 6. 



Hustedt, 1928, p. 396, fig. 207. 



Lebour, 1930, p. 49, pi. 1, fig. 4. 



Coscinodiscus stellaris var. fasciculata Castracane, 1886. 



Cells discoid, solitary. Valves convex, although often flattened in the middle. Valves 

 covered with very fine areolation ; areoles almost uniform in size throughout the whole 

 valve surface, slightly decreasing towards the margin. Centre of valve furnished with 

 a number of thickenings, usually three to six, arranged in a star-like pattern. Marginal 

 spinulae and apiculi absent. Girdle usually narrow, simple, finely striate. Chromato- 

 phores: numerous small rounded bodies. Diameter of valve 80-1 30/x. 



An oceanic Coscinodiscus, widely distributed throughout the Southern Ocean, equally 

 common in the northern hemisphere. It occurred frequently around South Georgia, 

 but was never observed in great numbers. 



Observed at Sts. 302, 304, 305, 542, 543, 544, 551, 552, 553, 615, 617, 619; WS 481. 



radiatae Rattray 

 Coscinodiscus Asteromphalus Ehrenberg. 



Ehrenberg, 1844, p. 77. 



Hustedt, 1928, p. 452, fig. 250. 



Coscinodiscus Asteromphalus var. conspicua Grunow ex Van Heurck, 1881-5, pi. 130, figs. 1, 2. 



Cells discoid, large, solitary. Valves slightly convex. Valve surface covered with a 

 strong areolation. A large central rosette enclosing a small structureless area. Areoles 



