(Castrac.) Mangin (Mangin) G.A.Fryxell & A.K.S.Prasad (1990: 34, figs 2–19)
Hemiaulus antarcticus Ehrenb. (Ehrenberg, 1844b: 203, fig. 8)
Eucampia antarctica (Castrac.) Mangin f. recta Mangin (1915: 63, figs 41–44)
Cells solitary, in doublets or straight to slightly curved chains, occurring as vegetative cells or heavily silicified ‘winter’ resting spores. Valves elliptical; apical axis 39–116 µm; areolae 7–8 in 10 µm. Horns of vegetative cells broad, flattened and ocellate (Fig. a). Labiate process solitary, c. 2 areolae from the margin. Vela are complex cribra (Fig. b). See Fryxell & Prasad (1990) for a full description.
Franklin I., 76°09’S 168°20.366’E, Ross Sea; Weddell Sea, 72°20.1’S and 74°39.12’S (Fryxell & Prasad, 1990).
The distribution of these two varieties overlap in the Weddell Sea, but while var. antarctica has a polar to subpolar distribution with a northernmost record at c. 56°S (Manguin, 1954), var. recta appears to be an Antarctic endemic, with a northernmost record at 64°48’S (Fryxell & Prasad, 1990).