SYSTEMATIC ACCOUNT 321 



Genus Guinardia H. Peragallo 

 Peragallo, H., 1892 



The genus Guinardia is included in the family Rhizosoleniaceae on account of the 

 small rudimentary spine which is placed in a marginal position upon the valve surface. 

 The cells are very weakly siliceous and the connective zone is composed of numerous 

 narrow intercalary bands. The chromatophores are usually stellate, but often become 

 degenerated and assume a subspherical form. The nucleus is often large and usually 

 central. The genus is neritic and, although seldom found in great numbers, is spread 

 widely, particularly in the southern hemisphere. 



Guinardia flaccida (Castracane) H. Peragallo. (PL XI, fig. 5.) 



Peragallo, H., 1892, p. 107, pi. 13, figs. 3, 4. 



Hustedt, 1929, p. 562, fig. 322. 



Lebour, 1930, p. 79, fig. 53. 



Karsten, 1906, p. 161, pi. 29, fig. 4. 



Gran, 1905, p. 24, fig. 25. 



Rhizosolenia? flaccida Castracane, 1886, p. 74. 



Rhizosolenia Castracanei Cleve, 1889, p. 54. 



Pyxilla baltica Hensen, 1887, p. 87. 



Cells usually large, solitary, but sometimes united to form short chains, seldom more 

 than six cells to one chain. Cells cylindrical, often slightly flattened. Valve flat or nearly 

 so, possessing a single rudimentary spine or spur placed near the margin. Connective 

 zone composed of numerous narrow intercalary bands, which owing to the weakly 

 siliceous nature of the cell are seen with great difficulty. If the cells are examined when 

 mounted dry, the annular segments are seen more easily, although the cell is apt to 

 collapse into an almost unidentifiable mass as a result of the drying. Chromatophores : 

 numerous stellate or rounded bodies, equally spread throughout the cell connected by 

 threads of plasma. Nucleus usually central. Diameter of cell 30-90^ ; pervalvar axis 

 usually 60-90/x. 



A neritic species, which occurs in most European waters, but seldom in great num- 

 bers. It favours a high salinity and was observed frequently around the Cape of Good 

 Hope. 



Observed at Sts. 260, 300, 425, 433, 434, 435, 666, 675. 



Family LEPTOCYLINDRACEAE 

 Subfamily LEPTOCYLINDROIDEAE 



1. Cells tubular, valves flat, connective zone composed of segments arranged spirally 



Dactyliosolen 



2. Cells tubular, valves flat or slightly convex, segments of connective zone not spirally 

 arranged Leptocylindrus 



