254 DISCOVERY REPORTS 



Coscinodiscus simbirskianus Grunow. 



Grunow, 1884, p. 81. 



Karsten, 1905, p. 86, pi. 6, fig. 5. 



Cells discoid, solitary. Valves flat or nearly so. Valves covered with radiating lines of 

 coarse granules arranged in fascicules. Striae parallel to the middle radius of each fasci- 

 cule. Central area and rosette absent. Puncta uniform in size throughout the whole 

 valve surface. Marginal spinulae and apiculi absent. Girdle narrow, striate, simple. 

 Chromatophores : numerous oval bodies. Diameter of valve Sofi. 



Observed at St. 664. 



Coscinodiscus subtilis Ehrenberg. 



Ehrenberg, 1843, p. 412, pi. 1, fig. 18. 

 Karsten, 1905, p. 86, pi. 7, fig. 11. 

 Lebour, 1930, p. 48, fig. 25 a. 



Cells discoid, solitary. Valves flat or nearly so, covered with very fine areolation. 

 Areolation arranged in two systems, consisting of a series of rather more distinct oblique 

 lines crossing radiating fascicules of parallel lines, and lines parallel to the middle radius 

 of each fascicule. Areolation entire, central area and rosette absent. Marginal spinulae 

 present, but rather difficult to see. Girdle simple, striate, narrow. Chromatophores: 

 numerous plate-like bodies. Diameter of valve 80-130^. 



This species has a wide distribution in subpolar seas. It was observed frequently 

 around South Georgia and appeared occasionally in the plankton taken around the 

 Cape of Good Hope. 



Observed at Sts. 260, 261, 475, 477, 478, 479, 480, 481, 482, 502, 506, 509, 510, 511, 

 512, 513, 664. 



Coscinodiscus trigonus Karsten. 

 Karsten, 1905, p. 84, pi. 5, fig. 10. 



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

 fine puncta arranged in radial fascicules, puncta in quincunx. Puncta uniform in size 

 throughout the whole valve surface. The valve possesses three marginal marks, or ribs, 

 arranged radially. Central hyaline area or rosette absent, spinulae absent. Chromato- 

 phores: a number of irregular bodies, consisting of four or five lobes. Diameter of 

 valve 80-96/u. 



A characteristic Antarctic form, having a wide distribution in the Southern Ocean, 

 neritic. 



Observed at Sts. 336, 337, 338, 505, 506, 507, 508, 509, 510, 666. 



Coscinodiscus variolatus Castracane. 



Castracane, 1886, p. 155, pi. 2, fig. 5. 

 Cells discoid, small. Valves flat or nearly so. Valve surface covered with puncta in 

 fascicules of parallel lines. Numerous small clusters of prominent granules are irregu- 



