G.Karst. (Karsten, 1905: 90, pl. 8, fig. 15)
Hustedt (1958: 128, figs 84–87), Priddle & Fryxell (1985: 120, figs a–f), Garrison et al. (1987: 566), Moisan & Fryxell (1993: 493)
Cells solitary, discoid. Valves slightly convex, 13.5–33 µm diameter; central hyaline area occupying half of valve diameter; 3–5 (–6) hyaline rays, one markedly narrower than the others, extending from centre almost to periphery of valve and ending in a protruding tubular process (Fig. a); rays often slightly curved. Separating lines within the central area genuflexed and branched. Peripheral sectors areolate; areolae 6–9 between the hyaline rays, of uniform size (Fig. b).
Cape Evans, Ross Sea; Southern Ocean south of Australia; coastal waters of Vestfold Hills, East Antarctica; Lützow-Holm Bay (Tanimura et al., 1990); Weddell-Scotia Sea (Garrison et al., 1987).
Some specimens examined for this study were slightly outside the previously recorded cell diameter range of 15–32 µm (Hasle & Syvertsen, 1997), but in all other respects they agree with earlier descriptions. A few specimens also had 6 hyaline rays (previous descriptions reported 3–5). This species is perhaps not as rare in the Antarctic and sub-Antarctic as was previously thought (Hargraves, 1968).