(Grunow) D.M.Williams & Round (1987: 276, figs 28–31)
Fragilaria brevistriata Grunow, in van Heurck (1880–85: 157, pl. 45, fig. 32)
Cells colonial, often united in short irregular chains by valve surfaces or poles, rectangular in broad girdle view; apical axis 12–28 µm; transapical axis 2–5 µm. Valves slightly cruciform; surface with a broad somewhat ill-defined sternum and short spines along the margin (8–19 in 10 µm) which link adjacent cells; spines enlarged at the tips. Transapical striae 13–17 in 10 µm, uniseriate, with 2–4 areolae per stria at the centre, and fewer at the poles; areolae comparatively large, circular to ovoid, sometimes extending below the spine into the mantle. Apical pore fields small, consisting of a few pores. Copulae non-areolate, numerous.
Plough I. and Ellis Fjord, near Davis Station, and coastal waters of Mawson Station and Casey Station, East Antarctica; type locality, “Eaux douce – Bruxelles (Delonge). Type no. 318” (Grunow, 1880).
The smallest cells are usually circular, or nearly so, whereas the largest are more commonly lanceolate. Intermediate forms produce such an uninterrupted series that it would be unwise to assign them taxonomic rank. The assemblage of forms can only be regarded as a polyphasic series.