Grunow Perag. (Peragallo, 1921: 68, pl. 3, fig. 7)
Cells united to form flat ribbon-like colonies; cells and colonies rectangular in girdle view; apical axis 80–90 µm; transapical axis 4–5 µm. Valves narrowly linear to lanceolate; valve ends elongate and capitate. Transapical striae 12 in 10 µm, with a narrow hyaline axial area that is more pronounced in the centre. Striae uniseriate; areolae poroid. Chloroplasts 2 narrow plates lying along the valve.
Type locality, Argentine Is., Antarctic Peninsula (Peragallo, 1921).
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.