SYSTEMATIC ACCOUNT 251 



ating with it. It has a sub-polar distribution, and has not been previously reported from 

 the Antarctic. It was found in large numbers around the South Sandwich Group. 

 Observed at Sts. 365, 368, 369; WS 100, 481. 



Coscinodiscus tumidus Janisch in Schmidt. 



Janisch (in Schmidt's Atlas), 1886, pi. 59, figs. 38-39. 

 Karsten, 1905, p. 80, pi. 6, fig. 1. 



Cells discoid. Valves convex, but often flattened in the centre. Valves covered with 

 hexagonal areolation ; areolation entire, central area and rosette absent. The areoles in- 

 crease gradually in size as they proceed to the periphery. Margin of valve usually 

 strong, sometimes wide, radially striate. Spinulae and apiculi absent. Girdle simple, 

 striate. Chromatophores : numerous irregular rounded bodies. Diameter of valve 

 100-140/i. 



Observed at one station only on the 30th W meridian at St. 664. 



FASCICULATAE Rattray 



Coscinodiscus Charcotii M. Peragallo. 

 Peragallo, M., 1921, p. 81, pi. 6, fig. 4. 



Cells discoid, somewhat small. Valves deeply convex with the central area slightly 

 flattened. Valve surface covered with fascicules of areoles in straight lines which radiate 

 from a central rosette of large areoles. The areoles decrease in size gradually as they 

 proceed to the margin of the valve. The actual margin of the valve is very narrow and 

 bears a ring of minute puncta. This species is characterized by the extreme dimensions 

 of the central areoles. Often they are five or six times as large as the areoles that occupy 

 the remainder of the valve surface. Diameter of cell 60-68/x. 



Type locality : Argentine Islands, on the Pacific side of the Graham Land Peninsula. 



This species was observed in the South Atlantic only at St. 677. 



Coscinodiscus Chunii Karsten. 



Karsten, 1905, p. 86, pi. 7, fig. 10. 



Cells discoid, solitary, valves slightly convex. Valves covered with fine but strong 

 areolation, in distinct radiating fascicules. Areolation very fine at the centre of the 

 valve, becoming larger towards the periphery. Margin of valve furnished with a num- 

 ber, usually six to eight, of elongated marks, which may be formed either by the breaking 

 down of the walls of adjacent cells, or by the production of a short rib. Chromatophores : 

 numerous small irregular bodies. Diameter of valve 120-140/u.. 



Observed at Sts. 475, 477, 478. 



Coscinodiscus curvatulus Grunow in Schmidt. 



Grunow (in Schmidt's Atlas), 1878, pi. 57, fig. 33. 

 Hustedt, 1928, p. 406, fig. 214. 



Coscinodiscus curvatulus var. enermis Grunow, 1884, p. 83. 

 Coscinodiscus szontaghii Pantocsek, 1886, p. 72, pi. 15, fig. 133. 



