Pterocystis latimarginalis  (Dürrschmidt, 1987) Siemensma, 1991
  
Diagnosis: Periplast 25 µm in diameter, with two types of scales; details of protoplast unknown. Spine scales spoon-shaped, consisting of shaft, lateral wings and basal wing. Shaft, 3-4 µm long and 0.1 µm thick, cylindrical, non-tapering, apically crenulated or abruptly cut off. Proximally, the shaft carries 2 smooth lateral wings in an almost V-form arrangement relative to the main axes and a basal wing, which spreads between the ventral edges of the lateral wings. The proximal shaft end is slightly curved outwards. Plate scales are elliptical or ovoid, 2-2.5 x 1.3-1.6 µm, bordered by a broad radially striated rim, which reaches its max. thickness near the inner edge of this rim. The distinctly denser appearance in TEM shows that this structure is hollow. The central area is smooth, except for a dark central line (axial thickening?).

Distribution: Sri Lanka, Malaysia.