Grunow, in Cleve & Grunow (1880: 53)
Hendey (1937: 348), Hasle & Syvertsen (1997: 282, pl. 62, tab. 71)
Cells solitary. Valves flat, lanceolate, slightly sigmoidal, with subacute ends; apical axis 180–270 µm; transapical axis c. 44 µm. Raphe straight or slightly sigmoidal; central endings deflected in the same direction; pole endings deflected in opposite directions. Valve striation fine, orientated in 3 distinct directions, one transverse and two oblique; oblique striae 18.5 in 10 µm.
Near Davis Station, East Antarctica; cosmopolitan (Hasle & Syvertsen, 1996); near South Georgia (Hendey, 1937); coastal waters off Syowa Station, East Antarctica (Ishikawa et al., 2001).
Hendey (1937) also reported P. smithianum Castrac. from Bransfield Strait. Published descriptions of that rare species are rather incomplete.