2 5 o DISCOVERY REPORTS 



puncta. Striae not very close together, simple ; central hyaline space absent. Puncta of 

 uniform size throughout the whole valve surface. Margin furnished with a ring of 

 stronger puncta, or small, short spinulae. Two distinct ribs or lines oppose each other 

 in a marginal position; ribs radial, often strongly marked. Girdle simple, minutely 

 punctate. Chromatophores : few angular or rounded bodies. Diameter of valves 

 46-52/*. 



A small Antarctic species seldom found in large numbers, widely distributed through- 

 out the Southern Ocean, probably oceanic. 



Observed at Sts. 453, 666. 



Coscinodiscus radiatus Ehrenberg. 



Ehrenberg, 1840a, p. 148, pi. 3, fig. 1. 

 Hustedt, 1928, p. 420, fig. 225. 

 Lebour, 1930, p. 39, fig. 15. 

 Coscinodiscus borealis Ehrenberg, 1862. 



Cells discoid, solitary, small to medium, thin. Valves mostly flat. Valves covered with 

 strong polygonal areolation, areolation entire, central hyaline area or rosette absent. 

 Areoles in radiating lines, lines long and short. Areoles usually of uniform size through- 

 out the whole valve surface, except at the margin, where they are much smaller. Girdle 

 simple, narrow, striate. Spinulae and apiculi absent. Chromatophores: numerous 

 cocciform bodies, often in clusters. Diameter of valve 70-140/t, mostly 100/x. 



An oceanic species having a world-wide distribution in temperate seas, which often 

 shows much variation in size, and coarseness of markings. Observed frequently off the 

 coasts of South Africa and often in large numbers in the Peru Current off the west coast 

 of South America. The latter appeared to be more robust. 



Observed at Sts. 260, 261, 262, 263, 379, 424, 425, 434, 436, 438, 439, 450, 460, 475, 

 575, 670, 671, 673, 681, 722, 723, 1583 ; WS 481, 641, 646, 647, 648, 649, 700, 703. 



Coscinodiscus sub-bulliens Jorgensen. 

 Jorgensen, 1905, p. 94, pi. 6, fig. 2. 



Cells discoid, valves clearly convex, with an evenly rising marginal zone. The central 

 area of the valve somewhat depressed, often flat. Valve surface covered with polygonal 

 areolations, no central space. No distinct central rosette of areoles usually present, but 

 an irregular grouping of five or six larger cells in the centre is common on larger speci- 

 mens. The areoles usually increase in size from the centre of the valve to about half the 

 radius, where they are largest, after which they suddenly decrease in size, but not pro- 

 gressively so, out to the periphery. Even in the area where the areoles are largest, a few 

 small ones are often interspersed. Areolate structure irregularly dichotomously radiate. 

 Margin furnished with small spinulae, and two larger apiculi, asymmetrically placed at 

 an angle approaching 180 . Girdle usually formed of a few intercalary bands. Chro- 

 matophores: several large flattened bodies. Diameter of valve 90-250/1, mostly 200^ ; 

 pervalvar axis 70-80^. 



This species is often confused with Coscinodiscus centralis, and is often found associ- 



