SYSTEMATIC ACCOUNT 249 



hyaline or structureless area. By the side of this central area is a short, stout process, 

 or nodule. The areoles present a complex secondary structure indicating an internal 

 chamber furnished with poroids. Margin of valve small or narrow, radially striate. 

 Diameter of valve ioo/n. 



This species was observed at one station only, off the South African coast, probably 

 meroplanktonic, never in great numbers. 



Observed at St. 434. 



Coscinodiscus oculoides Karsten. 



Karsten, 1905, p. 81, pi. 6, fig. 3. 



Van Heurck, 1909, p. 49, pi. 12, fig. 167. 



Cells discoid, solitary, medium to large. Valves convex, somewhat flattened towards 

 the centre. Valves covered with hexagonal areolation, arranged somewhat radially. 

 Areoles fairly uniform in size throughout the greater part of the valve surface, but de- 

 creasing in size gradually in the peripheral zone and upon the short valve mantle. 

 Central area and rosette absent. A small dot may be observed in the centre of each 

 areolation. Girdle simple, punctate, puncta in straight lines. Chromatophores : several 

 small rounded, or somewhat flattened plate-like bodies. Diameter of valve 140-200/x, 

 mostly 188/x. 



This species bears some resemblance to Coscinodiscus oculus-Iridis, but has an Ant- 

 arctic distribution only. A well-marked species, widely distributed throughout the 

 Southern Ocean, most probably neritic, but sometimes observed in oceanic plankton. 



Observed at Sts. 382, 452, 453, 480, 481, 482, 659, 661, 663, 664. 



Coscinodiscus oculus-Iridis Ehrenberg. 



Ehrenberg, 1840^7, p. 147. 

 Hustedt, 1928, p. 454, fig. 252. 



Cells discoid, solitary, large. Valves mostly flat or weakly convex. Valves covered with 

 large polygonal areolation, arranged in radiating lines, the lines long and short. Central 

 rosette often large, consisting usually of five areoles, sometimes less. Afeoles small at 

 the centre of the valve, increasing gradually in size as they proceed to the periphery. 

 Peripheral areoles usually much smaller. The areoles present secondary and tertiary 

 structure, in the form of an inner chamber and associated poroids. The opening of the 

 inner chamber provides that characteristic appearance known as the "eye-spot". 

 Girdle minutely punctate. Chromatophores : numerous rounded bodies. Diameter of 

 valve 1 80-260 fi. 



Probably an oceanic species, but in the material examined it was always found as a 

 meroplanktonic form. Frequent around the coast of South Georgia. 



Observed at Sts. 425, 508, 677; MS 94, 95, 97, 98, 100, 101, 102, 103. 



Coscinodiscus oppositus Karsten. 



Karsten, 1905, p. 82, pi. 7, fig. 5. 

 Cells discoid, solitary, small. Valves flat. Valves covered with radiating lines of small 



