2S 2 DISCOVERY REPORTS 



Cells discoid, solitary. Valves almost flat, covered with coarse areolation. Areoles 

 arranged in fascicules of curved lines. The first line of each fascicule runs from the 

 centre of the valve to the margin, other shorter lines fill the sector, running parallel with 

 the first line. Areoles polygonal, attaining their maximum size at a distance equal to half 

 of the radius. Valve surrounded by a narrow margin, with short radial lines. Marginal 

 apicules present at the end of the radial line of each fascicule, central area or rosette 

 absent. Chromatophores : several rounded bodies. Diameter of valve 75-90/i. 



An oceanic species having a wide distribution in temperate seas. 



Observed at Sts. 334, 336, 337, 477, 661, 664, 666, 673, 675, 677. 



Coscinodiscus gracilis Karsten. 

 Karsten, 1905, p. 78, pi. 3, fig. 4. 



Cells discoid, very small, solitary. Valves strongly convex, with wide flattened edge or 

 margin. Margin marked with radial lines. Surface of valve covered with granules, large 

 and somewhat sparse in the centre, smaller and more dense in the peripheral zone. 

 Chromatophores: few small irregular bodies. Diameter of valve 20^. 



A small neritic Coscinodiscus form, found only in the South Atlantic. It favours cold 

 water and low salinity. 



Observed at St. 666. 



Coscinodiscus grandenucleatus Karsten. 

 Karsten, 1905, p. 86, pi. 7, fig. 9. 



Cells discoid, solitary, valves convex. Valves covered with fine punctation arranged 

 in fascicules of parallel lines ; a second system of lines is radially arranged. Central area 

 and marginal spines absent. Chromatophores : numerous irregular bodies, nucleus very 

 large, absorbing dye readily. Diameter of valve 66-76^. 



A typical neritic species of Antarctic Coscinodiscus. Observed occasionally around 

 South Georgia, but never in great numbers. 



Observed at Sts. 338, 339, 340. 



Coscinodiscus hexagonalis Karsten. 

 Karsten, 1905, p. 87, pi. 3, fig. 8. 



Cells discoid, solitary. Valves nearly flat at the centre, sharply convex at the peripheral 

 area. Valves covered with small but regular hexagonal areolation. Areoles small at the 

 centre, slightly increasing in size up to a distance of half the radius, after which little or 

 no increase in size is noticed. A small dot or poroid is clearly discernible at the base or 

 floor of each areole. Central area and rosette absent. Marginal spinulae absent, girdle 

 simple. Chromatophores: few plate-like bodies. Diameter of valve 160 -190/x. 



Observed at Sts. 460, 461. 



Coscinodiscus incurvus Karsten. 

 Karsten, 1905, p. 85, pi. 7, fig. 8. 

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

 puncta arranged in parallel lines. Central area of valve devoid of structure, puncta more 



