B.C.Booth & H.J.Marchant (1987: 248, figs 2 (holotype), 3)
Booth et al. (1981: 76, figs 60–62, as “Cyst IX”), Marchant & McEldowney (1986: 54, fig. 5), Kosman et al. (1993: 123, fig. 31)
Cells planktonic, solitary, non-motile, spherical, 2.2–2.8 µm diameter. Cell wall comprising 8 siliceous plates: 4 shield plates and 4 triradiate plates, all fitting edge to edge, with raised rims; all plates with branching veins, with or without surface papillae. Shield plates circular, 1.7–2.2 µm diameter, with a central projection to 3.5 µm long. Triradiate plates with arms c. 1.3 µm long. Papillae arranged in rows radiating from the centre, 10 per micrometre, variously developed on different specimens.
Surface waters of Prydz Bay, East Antarctica; North Pacific, Bering Sea, eastern equatorial Pacific, Greenland and Finland (Kosman et al., 1993).