Pterocystis pteromorphos (Dürrschmidt, 1987) Siemensma, 1991
Diagnosis: Periplast small, 10-15 µm in diameter (measurement based on whole mount); details of protoplast unknown. Spine scales 2-2.5 µm long, consisting of shaft, lateral wings and basal wing. Shaft, 0.09 µm in diameter, slightly bent and hollow. Apex of the shaft abruptly cut off at right angles without taper. Lateral wings max. 0.4 µm broad, mutually positioned at an angle of 180°, taper distally along the spine shaft to terminate sub-apically. Horizontally directed slits are present irregularly. The basal wing is almost rectangular and smooth. Plate scales, 2.1xl.2µm, are elliptical, patternless except for a faintly elaborated axial thickening.