284 DISCOVERY REPORTS 



point of confluence. The spines of the marginal row are often joined together to form 

 an outer palisade or fenestrated superstructure. The girdle is simple and finely punctate. 

 Chromatophores : numerous rounded bodies. Distance between the angles 86/n, 

 pervalvar axis 40/x. 



A littoral species frequent around the North Sea coasts and the sea-board on both sides 

 of the Atlantic. This species was observed at one station only, off South Africa. The 

 specimens were very few, small and by no means so elegant as those obtained from the 

 North Sea. Type locality: Cuxhaven. 



Observed at St. 436. 



Genus Ditylum L. W. Bailey 

 Bailey, 1862 



The genus was described first to the Boston Society of Natural History in September 

 of 1 86 1, and was published in the Proceedings of that Society in the following year 

 (vol. vni, 1862) and later in the Boston Journal of Natural History (vol. vn, 1862), where 

 illustrations were provided. Two species were described, D. trigonum and D. inaequale. 

 The first, which is usually considered as the type, had been described previously by 

 Tuffen West as Triceratium Brightwellii (West, i860). It must be assumed that Bailey 

 was unaware of West's paper. 



Grunow, in Van Heurck's Synopsis (1880-5) made the combination Ditylum Bright- 

 wellii (West) and placed both Bailey's species as synonyms. 



The generic name is often spelt wrongly as Ditylium. The genus was discovered by 

 the father of the author (J. W. Bailey) in material from the Para River. 



Ditylum Brightwellii (West) Grunow ex Van Heurck. (PI. XII, figs. 5, 6.) 



Van Heurck, 1885, p. 196. 



Gran, 1905, p. 112, pi. 150. 



Hustedt, 1930, p. 784, fig. 457. 



Lebour, 1930, p. 186, fig. 146. 



Triceratium Brightwellii West, i860, p. 149, pi. 7, fig. 6. 



Ditylum trigonum Bailey, 1862, p. 163. 



Ditylum inaequale Bailey, 1862, p. 163. 

 Cells triangular in shape, somewhat like a prism, angles rounded so as to give a cylin- 

 drical appearance. Cells three to eight times longer than broad. Valves small, undulate, 

 furnished with a corona of short but stout spines surrounding one large central spine. 

 Central spine straight. Central area of valve often raised, hyaline. Girdle elongated. 

 Lebour (1930) described the connecting zone as composed of scale-like intercalary 

 bands. Chromatophores: numerous cocciform bodies, usually grouped towards the 

 centre of the cell. Cells very weakly siliceous. Diameter of valve 28-46/x ; pervalvar axis 

 80-130^ ; length of spine 20-50^. 



A neritic species, widely distributed throughout temperate and subtropical seas. It 

 was observed frequently around the coasts of South Africa, the Falkland Islands, and 

 in the Pacific Ocean. 



Observed at Sts. 260, 262, 436, 722, 723 ; WS 105, 107, 710. 



