276 DISCOVERY REPORTS 



short but thick processes. Central area of valve slightly convex. Valve mantle deep, 

 somewhat constricted as it meets the girdle or connective zone. Valve covered with 

 puncta arranged in radiating lines. Puncta often sparse at the central area. Central area 

 furnished with usually two stout spines placed together, spines divergent. Spines some- 

 times absent. Girdle deep, furnished with lines of puncta, interrupted by usually two 

 hyaline bands. The frustules are found united together in zigzag chains by means of 

 small cushions of mucous exuded at the processes. Chromatophores : numerous rounded 

 or oval bodies. Polar axis 84^ ; pervalvar axis 124^.. 



A littoral species, frequently found around European coasts. It was observed in small 

 numbers around South Georgia and in the Bransfield Strait. 



Observed at Sts. 670; WS 481. 

 Biddulphia longicruris Greville. 



Greville, 1859 b, p. 163, pi. 8, fig. 10. 



Cells gonioid, often united to form chains. Four to twenty cells in a chain. Cells in 

 valve view bipolar. In girdle view the valves show a prominent central inflation which 

 bears a stout spine. The angles of the valves are produced to long slender processes. 

 The valve surface is minutely punctate, puncta irregularly arranged and somewhat 

 sparse. Chromatophores : numerous rounded bodies. 



This species occurred frequently in the Peru Current. It is a neritic form which has 

 a wide distribution in temperate and tropical seas, but has not been recorded from 

 English waters. Type locality : Californian guano. 



Observed at Sts. WS 593, 594, 598, 622. 



Biddulphia mobiliensis (Bailey) Grunow ex Van Heurck. (PI. XII, fig. 9.) 



Van Heurck, 1880-5, P 1 - I0I > % s - 4 -6 - 



Gran, 1905, p. 106, fig. 138. 



Hustedt, 1930, p. 840, fig. 495. 



Karsten, 1905, p. 121, pi. 17, fig. 1. 



Lebour, 1930, p. 174, fig. 134. 



Zygoceros mobiliensis Bailey, 1851, p. 40, pi. 2, fig. 34. 



Cells solitary, but sometimes united to form short chains. Cells in girdle view, 

 shortly rectangular, in valve view elliptical to elliptic-lanceolate. The poles of the valves 

 are produced to form long narrow processes. Valve mantle gently curved inwards be- 

 neath the processes to meet the girdle. Central area of the valve raised, flattened, or 

 weakly concave, and furnished with two long, straight spines. Spines divergent, the 

 distance between the spines only a little more than the distance between a spine and the 

 apical process. The entire cell is covered with extremely fine areolation, which is seen 

 only with the greatest difficulty. It may be observed more easily if the cells are ex- 

 amined when mounted dry. Chromatophores: numerous rounded bodies. Polar axis 

 80/x ; pervalvar axis 100/-1. 



The species is widely distributed in both hemispheres. A weakly siliceous diatom ; 

 pelagic, but often associated with a coastal flora, and sometimes found in great numbers. 



Observed at Sts. 260, 261, 434, 1373. 



