Grunow Manguin (1960: 298, pl. 12, fig. 128)
Hasle et al. (1994: 255, figs 56, 76–78)
Cells united to form flat ribbon-like colonies; cells and colonies rectangular in girdle view; apical axis c. 21–36 µm; transapical axis c. 3.5 µm. Valves narrowly linear to lanceolate; valve ends elongate and subcapitate. Transapical striae 13–16 in 10 µm, with a narrow hyaline axial area in the centre. Striae uniseriate; areolae poroid, c. 40 in 10 µm. Apical pore field comprising short rows of areolae (Fig. 2.76e). Labiate process slit-like, located at valve pole.
Ellis Fjord, near Davis Station, East Antarctica; Terra Nova Bay, Ross Sea; type locality, Terre Adélie, 66°50’S 141°25’E (Manguin, 1960).
Material identified as F. islandica var. adeliae and reported for McMurdo Sound by Grossi & Sullivan (1985) is possibly Synedropsis recta (see p. 144).
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.