SYSTEMATIC ACCOUNT 241 



the Chilean coast, but never occurred in great numbers. A neritic species confined to 

 temperate waters ; it has not been recorded in the northern hemisphere. 

 Observed at Sts. 425, 427, 428, 433, 434, 43 6 ; ws 7°9> 7 I0 > 7 J 4> 7 I 5« 



Genus Schroderella Pavillard 

 Pavillard, 191 3 



Schroderella delicatula (Peragallo) Pavillard. 



Pavillard, 1913, p. 126. 



Pavillard, 1925, p. 22, fig. 33. 



Lebour, 1930, p. 68, fig. 40. 



Hustedt, 1929, p. 551, fig. 314. 



Lauderia delicatula Peragallo, H., 1888, p. 89, pi. 6, fig. 46. 



Detonula delicatula Gran, 1900a, p. 112. 

 Cells cylindrical, elongated about the principal axis. Valves circular more or less 

 convex, but mostly flat, with short, sharply curved peripheral zones. Centre of valve 

 depressed, furnished with short central spine, often united to form chains. Margin of 

 valve furnished with a row of short sharp spines, which interlock with those of the 

 neighbouring frustules. Valve almost without structure. Girdle composed of annular 

 segments which are finely areolate. Chromatophores : numerous small rectangular or 

 stellate plates. Diameter of valve 20-35/* '> pervalvar axis up to 110/1. 



A neritic species, very common around South Africa. It favours warm water of fairly 

 low salinity, has been recorded from the Atlantic, west coast of Africa and the 

 Mediterranean. 



Observed at Sts. 425, 427, 428, 434, 435, 437, 43 8 - 439- T 373- 



Schroderella Schroderi (Bergon) Pavillard. 



Pavillard, 1925, p. 23, fig. 33. 



Lebour, 1930, p. 68, fig. 41. 



Lauderia Schroderi Bergon, 1902 ft, p. 69. 



Cells shortly cylindrical or oblong, united to form loose chains. Valves circular, 

 convex, centrally depressed, furnished with a central spine. Valves almost devoid of 

 definite structure, but the margins are furnished with rows of well-developed spines. 

 Girdle composed of annular segments, finely areolate. This species is very close to the 

 foregoing one, Hustedt (1929) unites them. Here they are regarded as being separate 

 on the grounds that S. Schroderi is usually greater in diameter and less in pervalvar axis 

 than S. delicatula, and that the spaces between the cells are well marked and the spines 

 more prominently developed in the former. Further, generally speaking S. Schroderi 

 favours colder water. A neritic species. Chromatophores: numerous small angular 

 plates. Diameter of valve 20-55/x ; pervalvar axis 18-40/i. 



Distribution is very difficult to define, as it probably has been much confused with 

 the previous species. A northern form, reported from the Atlantic Ocean, and English 

 Channel. It was found to be fairly abundant in the Peru Current material. 



Observed at Sts. 434, 436, 1373; WS 593, 594, 640, 665, 666, 705, 709, 710. 



