2 4 8 DISCOVERY REPORTS 



Coscinodiscus lentiginosus Janisch in Schmidt. 



Janisch (in Schmidt's Atlas), 1878, p. 58, fig. 11. 

 Castracane, 1886, p. 160, pi. 5, fig. 4. 

 Karsten, 1906, p. 155, pi. 26 m, fig. 11. 



Cells discoid, solitary, small. Valves nearly flat, margin strong. Valve surface covered 

 with granules which are somewhat irregularly disposed throughout the central area of 

 the valve, but arranged in short radial lines, somewhat closely packed toward the valve 

 margin. Between the radial lines and the margin of the valve is a narrow hyaline space 

 which completely encircles the punctate portion. Margin strong, narrow, finely radially 

 striate, furnished with one apiculus. Chromatophores : several large irregular bodies. 

 Diameter of cell 40-1 20^. 



Type locality, Antarctic Ocean. A characteristic Antarctic diatom, widely spread 

 throughout the South Atlantic. 



An examination of the deep-sea ooze from the vicinity of Tristan dAcunha showed 

 that an enormous deposit of diatomaceous material was being formed which consisted 

 very largely of this species. 



Observed at Sts. 383, 384, 453, 475, 477, 482, 502, 504, 508, 570, 575-577; ws 545- 

 548-552A. 



Coscinodiscus marginatus Ehrenberg. 



Ehrenberg, 1843 b, p. 412. 

 Hustedt, 1928, p. 416, fig. 223. 

 Coscinodiscus limbatus Ehrenberg, 18406. 

 Coscinodiscus fiinbriatus-limbatus Ehrenberg, 1854. 



Cells discoid, solitary, strong. Valves flat or nearly so, particularly at the centre. 

 Valves covered with strong and large areolation, areoles polygonal, central hyaline area 

 absent. Areoles arranged somewhat irregularly radial, attaining their maximum size at 

 about half the radius of the valve ; peripheral areoles smaller. Valve surrounded by a 

 broad flat margin, strongly striate radially. The areoles of the valves present a complex 

 structure, showing an internal and lower chamber, surrounded by a ring of fine poroids. 

 Chromatophores: several small rounded bodies. Diameter of valve 44-80^. 



This species is common in all temperate seas, but was not observed in great numbers. 

 Probably a bottom form, meroplanktonic, but sometimes observed a considerable dis- 

 tance from land. 



Observed at Sts. 675, 677, 1586. 



Coscinodiscus nodulifer Janisch in Schmidt. 



Janisch (in Schmidt's Atlas), 1878, pi. 59, figs. 21-23. 

 Karsten, 1907, p. 364, pi. 36, fig. 6. 

 Hustedt, 1928, p. 426, fig. 229. 



Cells discoid, solitary. Valves flat or weakly convex, covered with strong polygonal 

 areolation. The areoles attain their maximum size at about half the radius of the valve, 

 after which they decrease. The areolation often breaks down at the centre to form a small 



