33 o DISCOVERY REPORTS 



Suborder ARAPHIDINEAE 



Family FRAGILARIACEAE 



Subfamily FRAGILARIOIDEAE 



i. Cells linear, united in ribbon-like bands, valves finely striate, narrow axile area ... Fragilaria 



2. Cells linear to linear-lanceolate, united in ribbon-like bands, axile area absent, transverse 

 lines of puncta alternate with hyaline ridges Fragilanopsis 



3. Cells solitary or in tufted colonies, valves striate, small rounded or rectangular central area 



_,. Synedra 



present ... ... ... ••• ••• ••• ••• ••• J 



4. Cells united in zigzag chains, valves usually hyaline, marginal spines Thalassionema 



5 . Cells solitary, spirally twisted or slightly sigmoid, apices sometimes unequal .. . Thalassiothrix 



6. Cells clavate, arranged in stellate or spirally twisted colonies Asterionella 



Subfamily TABELLARIOIDEAE 



1. Cells rectangular, united in zigzag chains, internal septa straight Rhabdonema 



2. Internal septa undulate Grammatophora 



3. Cells cuneate in girdle view, clavate in valve view Licmophora 



4. Cells linear in valve view, arcuate in girdle view Entopyla 



Subfamily FRAGILARIOIDEAE 



Genus Fragilaria Lyngbye 

 Lyngbye, 18 19 

 This genus is represented by several species, all of which are neritic. The species are 

 colonial, and the cells adhere valve to valve, giving rise to flat ribbon-like bands. Some 

 of the species recorded were associated with melting ice, and those obtained near 

 St. 560 were obtained from melted ice taken at a position in approximately 66° S, 

 6o° W. These included Fragilaria curta which must be considered as characteristic of 

 the coastal diatom flora of the land-masses within the Antarctic convergence. 



Fragilaria curta Van Heurck. 



Van Heurck, 1909, p. 24, pi. 3, fig. 37. 



Cells small, united to form short chains, but often solitary. Valves oblong, with 

 rounded ends, sides straight, parallel. Valve-surface furnished with numerous delicate 

 transverse striae. Striae straight and parallel in the median area of the valve, but slightly 

 curved towards the apices. Connective zone simple. Chromatophores : several small 

 plates. Apical axis of cell 24-30^ ; transapical axis 8/x. Type locality, melted ice from 

 Antarctic Ocean. 



Probably a neritic species : obtained in great numbers from melted ice. 



Observed near St. 560. 



Fragilaria granulata Karsten. 



Karsten, 1907, p. 396, pi. 54, fig. 8. 

 Cells united to form short chains, from four to twelve cells in a chain. Chains curved 



