Triceratium parallelum (6 angles) from the Red Sea. Single example on the slide. Prepared by William Allott Firth. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 29 images stacked in Zerene (Pmax).
Triceratium parallelum (Ehrenberg) Greville 1865. Published in: Greville, R.K. (1865). Descriptions of new and rare diatoms. Series XVII. Transactions of the Microscopical Society, New Series, London 13: 97-105, 2 pls [VIII, IX]. Page 104, Plate IX [9], Figures 22,23. In this Greville mentions that these are present in the Red Sea dredgings and are seen as 4 and 6 sided versions. In my copy of this, which is an assembly of the articles from 1968, it mentions that Triceratium parallelum = Stictodiscus parallelus which makes sense based on their appearance.