242 DISCOVERY REPORTS 



Subfamily COSCINODISCOIDEAE 



Genus Coscinodiscus Ehrenberg 

 Ehrenberg, 1838 



INORDINATAE Rattray 

 Coscinodiscus nitidus Gregory. 



Gregory, 1857, p. 499, pi. 10, fig. 45. 

 Karsten, 1905, p. 84, pi. 7, fig. 1. 

 Hustedt, 1928, p. 414, fig. 221. 



Cells discoid, small. Valves flat or nearly so. Valves covered with somewhat large 

 granules, showing an irregular radial arrangement. Granules sparse, rounded, large in 

 the centre of the valve, decreasing in size as they approach the periphery. Margin of 

 the valve furnished with short radial lines of small puncta, three to four puncta in each 

 line. Chromatophores : several irregular plate-like bodies. Diameter of valve 58^. 



A well-marked species fairly common around European coasts, but was observed at 

 one Station only off South Georgia. Meroplanktonic, probably a bottom form. 



Observed at St. 479. 



excentricae Rattray 

 Coscinodiscus excentricus Ehrenberg. 



Ehrenberg, 1840a, p. 146. 



Gran, 1905, p. 29. 



Hustedt, 1928, p. 388, fig. 201. 



Lebour, 1930, p. 36, fig. 13. 



Coscinodiscus labyrinthus Roper, 1858, p. 21, pi. 3, fig. 2. 



Coscinodiscus heliozoides Siddall, 191 2, p. 377, pi. 3. 



Cells discoid, small, solitary. Valves flat or nearly so. Valves covered with strong 

 hexagonal areolation, in ill defined sectors of curved and somewhat parallel lines, but 

 often tangential. Sectors usually seven, but may be six or eight. Central areoles usually 

 larger than peripheral ones. Margin of valve furnished with a number of stout but short 

 apiculae. Siddall (1912), noticed in fresh material gathered at Bournemouth, a number 

 of radiating protoplasmic threads proceeding from the valves, and upon this feature 

 created a new species, C. heliozoides. This phenomenon is, however, of no specific im- 

 portance, and is to be observed in many species of the Coscinodiscaceae when fresh. 

 Chromatophores: several small flat plates. Diameter of valve 40-140^, mostly 100/i; 

 pervalvar axis 30/n. 



A widely distributed species showing much variation. Specimens from around the 

 Cape of Good Hope were unusually large. 



Observed at Sts. 386, 434, 451, 501, .670, 671. 



LINEATAE Rattray 

 Coscinodiscus lineatus Ehrenberg. 



Ehrenberg, 1839, p. 129. 

 Hustedt, 1928, p. 392, fig. 204. 



