(Hust.) Medlin, in Medlin & Hasle (1990b: 473, fig. 14)
Nitzschia compacta Hust. (Hustedt, 1958: 169, fig. 160)
Paddock & Sims (1980: 161), Simonsen (1987: 450, pl. 670, fig. 1, as N. compacta), Medlin & Hasle (1990a: 159, pl. 21.1, fig. 11)
Cells solitary, asymmetrical, elliptical (girdle view) to auriculate or reniform (valve view); apical axis 79–134 µm; transapical axis 12–13 µm, with a curved strongly ridged keel supporting the raphe and dividing the valve into a broad and narrow face. Fibulae 6–9 in 10 µm; striae 22–27 in 10 µm, parallel in mid-region of valve, radiating outwards towards the valve ends, containing double rows of small areolae. Central nodule present. Copulae numerous, simple (Fig. c).
Offshore from Ranwick Glacier, Prydz Bay, East Antarctica; Inexpressible I., Ross Sea; type locality, 69°43’S 06°30’E (Hustedt, 1958); Antarctic sea-ice (Medlin & Hasle, 1990b).
Nitzschia medioconstricta has a similar morphology to Auricula compacta, but the cells are usually shorter and thinner and have a greater density of fibulae.
Auricula compacta has a similar morphology to Nitzschia medioconstricta , but cells of the latter are usually shorter and thinner and have a greater density of fibulae than A compacta.