Grunow Perag. (Peragallo, 1921: 68, pl. 3, fig. 8)
Cells united by valve faces to form flat ribbon-like colonies; cells and colonies rectangular in girdle view; apical axis 87–100 µm; transapical axis 6–7 µm (3 µm at apices). Valves narrowly linear to lanceolate. Transapical striae 14 in 10 µm, with a narrow hyaline axial area that is more pronounced in the centre. Striae uniseriate; areolae poroid. Areolae 50 in 10 µm; apical pore field comprising c. 24 × 5 pores on the apical valve mantle. Chloroplasts 2 narrow plates lying along the valve.
Inexpressible I., Ross Sea; type locality, Argentine Is., Antarctic Peninsula (Peragallo, 1921).
Cells collected in the present study were 87 µm long and c. 7 µm wide in valve view.
Fragilaria is now regarded as an exclusively freshwater genus (see Williams & Round, 1987; Round et al., 1990). Thus, the Antarctic species listed below (Fragilaria islandica and its varieties) should probably be transferred to a different and possibly new genus. The apical field structure of pores (cf. slits) helps to distinguish Fragilaria from Synedropsis.