SYSTEMATIC ACCOUNT 247 



Girdle cuneate, valve often shows greater convexity at a point other than the centre, 

 usually towards the side upon which the girdle band is widest. Valve furnished with two 

 asymmetrically placed processes, or apiculi. Chromatophores : numerous oval or 

 rounded bodies. Diameter of valve ioojj.; girdle, wide end 20/x, narrow end 10/i. 



This diatom is frequent in the North Sea, and most northern European waters. It has 

 been recorded from the English Channel, and has apparently spread into the Atlantic. 

 It was observed at two stations off South-West Africa, but not in great numbers. The 

 eccentricity of the convexity of the valves was not nearly so marked as that illustrated by 

 Hustedt (1928) and Lebour (1930), but resembled more closely that illustrated by 

 Gough (1905). 



Observed at Sts. 263, 264. 



Coscinodiscus intermittens Karsten. 

 Karsten, 1906, p. 156, pi. 26, fig. 14. 

 Cells discoid, solitary. Valves slightly convex, but often quite flat in the centre. 

 Valves covered with fairly coarse puncta arranged in radial lines. A small cluster of 

 usually seven to ten granules occupies the centre of the valve ; these are surrounded by 

 a hyaline space. Many of the radial lines of granules fail to reach the centre, giving rise 

 to a number of interstitial hyaline spaces and a false fasciculate appearance. Puncta are 

 of uniform size throughout the whole valve surface with the exception of those at the 

 margin. Marginal puncta very small, forming close radial lines of six or eight puncta in 

 each. Margin of valve furnished with small but prominent spinulae. Girdle simple, 

 punctate. Chromatophores: numerous small cocciform bodies. Diameter of valve 



90-I IO(U. 



A handsome species found only in the Southern Ocean. Neritic, observed only in 

 moderate numbers. 

 Observed at St. 440. 



Coscinodiscus kerguelensis Karsten. 

 Karsten, 1905, p. 83, pi. 3, fig. 7. 



Cells discoid, solitary, large. Valves convex, nearly flat at the centre, but with con- 

 siderable valve mantle. Valves covered with fine punctation radially arranged. Puncta 

 in central area of valve smaller than those in the peripheral area and more closely 

 arranged. Central area also traversed by secondary line system, imparting to that area 

 an appearance of definite demarcation. Margin of valve strong, clearly marked with 

 small closely packed radial lines. The whole surface of the valve is covered by occasional 

 darker dots arranged in irregular radial lines, which appear to be superimposed upon 

 the primary structure. Chromatophores: numerous small rounded or oval bodies. 

 Diameter of valve 100-180/x, usually 165/x; pervalvar axis 8o/jl. 



A large and handsome species found only in the Antarctic Ocean, and observed in 

 considerable numbers in the Bransfield Strait. A meroplanktonic form, not often ob- 

 served in the plankton, probably epiphytic upon larger algae. 



Observed at St. WS 481. 



D XVI 13 



