SYSTEMATIC ACCOUNT 351 



Family CYMBELLACEAE 



Subfamily CYMBELLOIDEAE 



1. Pervalvar axis slightly curved, zone simple ... ... ... ... ... ... Cymbella 



2. Pervalvar axis strongly curved, zone usually complex ... ... ... ... ... Amphora 



Genus Amphora Ehrenberg 



Amphora Peragallorum Van Heurck. 

 Van Heurck, 1909, p. 7, pi. 1, fig. 2. 



Valves elongated, weakly cymbiform, with very obtuse extremities, slightly capitate. 

 Dorsal margin weakly arcuate, ventral margin almost straight. Raphe very close to and 

 almost parallel with the ventral margin. Raphe very prominent, straight. Valve surface 

 furnished with robust striation, striae short, confined to the dorsal half of the valve 

 surface, the ventral half being quite hyaline. Apical axis of cell 60-1 io/m. 



Observed at St. WS481. 



Family BACILLARIACEAE 



Subfamily NITZSCHIOIDEAE 



1 . Cells linear, with marginal keel, valves finely striate Nitzschia 



2. Cells naviculoid, raphe eccentric, valves finely striate Chttniella 



Genus Nitzschia Hassall 

 Hassall, 1845 



It has been explained under Pleurosigma that Nitzschia Hassall (1845) is an absolute 

 synonym of Sigmatella Klitzing (1833 a), as both genera are based upon Bacillaria 

 sigmoidea Nitzsch. However the name Nitzschia is used here, until it is legally con- 

 served, in the sense that most modern taxonomists have used it ; that is, in the sense that 

 Wm Smith used it in his Synopsis of British Diatomaceae (1853); taking Nitzschia 

 sigmoidea Wm Smith based on Sigmatella Nitzschii Kiitzing, which was Bacillaria 

 sigmoidea Nitzsch, as the type of the genus. 



Nitzschia Barbieri M. Peragallo. 



Peragallo, M., 1921, p. 66. 



Nitzschia Ostenfeldii, var. minor Van Heurck, 1909, p. 22, pi. 3, fig. 177. 



Cells usually solitary. Valves linear-oblong with margins parallel, and subobtuse 

 apices. Valve surface furnished with bold transverse striae, slightly curved towards the 

 apices, but straight in the median area of the valve. Each striation is terminated by a 

 strong carinal dot. Connective zone simple. Apical axis of cell 80-1 50/i. 



D XVI 26 



