H.-J.Schrad. (Schrader, 1972: 59, pl. 1, 2)
Hasle (1983: 223, figs 19–36), Hasle & Syvertsen (1997: 57, tab. 7)
Cells chain-forming, united by chitinous threads from the off-central strutted process, sometimes in gelatinous masses, discoid to rectangular in girdle view; pervalvar axis equal to or greater than valve diameter. Valves circular, 6–16 µm diameter, flat to slightly convex, thin-walled so that cells collapse easily, with radial ribs or rows of fine areolae (not visible by LM). Areolae 40–60 in 10 µm on the valve face and mantle. Areolation of copulae and valvocopulae fine, irregular (Fig. c). Strutted processes in one marginal ring, 3–5 in 10 µm, operculate, each with an external (Fig. b) and internal extension; 1 strutted process in off-centre position, occasionally with 4 or 5 smaller satellite pores (Fig. d). Labiate process solitary, midway between 2 of the marginal strutted processes (Fig. a, b), internally slit-like and radially orientated.
Southern Ocean, south of Australia; type locality, upwelling area off Cape Blanc, North Atlantic (Schrader, 1972); offshore West Africa and Peru (Hasle, 1983); “mainly warm water region” (Hasle & Syvertsen, 1997); Gulf of Carpentaria and North-West Shelf, Australia (Hallegraeff, 1984).
This is apparently the first record of this species from polar waters.