Griessm. (Griessmann, 1913: 31, fig. 11)
Vørs (1992a: 43, figs 20a–i, 21.10), Patterson et al. (1993: 74, fig. 2J), Tong et al. (1997: 99, fig. 3D)
Cells oval to bean-shaped, 4–10 µm long, 2–6 µm wide, dorsoventrally flattened, biflagellate. Flagella merging subapically, unequal; long flagellum trailing, 1–2 times cell body length; short flagellum directed forwards, 0.5–1 times cell body length.
Antarctic Ocean, south of Australia; Disko Bay, Greenland, Baltic Sea (Vørs, 1992a).
Specimens collected in the Southern Ocean were slightly smaller (3.6 × 1.8 µm) than those previously documented.