Pterocystis tropica (Dürrschmidt, 1987) Siemensma, 1991
Diagnosis: Periplast 20-30µm in diameter; details of protoplast unknown. Scales of two types. Spine scales, 4-7 µm long, consisting of shaft, lateral wings and basal wing. They are usually bent in the proximal half of their length. Shaft, 0.19 µm in diameter, hollow, tapering abruptly to a pointed apex. The lateral wings are proximally rectangular but then narrow abruptly and taper distally along the shaft to terminate sub-apically. The outer corners thus formed are sometimes expanded. Cross ribs are developed, mainly on the proximal part of the lateral wings and on the basal wing. Plate scales, 2.1-2.7 x 1.2-1.5 µm, elliptical, ornamented with distinct radial slits and a moderately elaborated axial thickening.
Remarks: P. tropica bears some likeness to E. erinaceoides and P. pinnata, for instance in the spatulate appearance of the spine scales, the curved, tapering shafts, the triangular basal wing, as well as in the broad lateral wings which narrow abruptly. Distinguishing characteristics are the rib-pattern present on the wings and the ornamentation of the plate scales. These lack the central swelling, which is typical of E. erinaceoides and P. pinnata.
Distribution: Sri Lanka.