Triceratium harrisonianum from Springfield, Barbados. Single example on the slide. Prepared by Thomas W Robertson, and dated 1916. 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. 23 images stacked in Zerene (Pmax).
Described in: Greville, R. K. (1861). Descriptions of new and rare Diatoms. Series III. Transactions of the Microscopical Society, New Series, London. 9: 73-77. Plate IX, Figure 9. It is mentioned as being ‘exceedingly rare’.
As a note, the name Triceratium harrisonianum doesn’t sit right with me. This does not look like a Triceratium, the overall structure looks more like a Stictodiscus sp. specifically Stictodiscus buryanus. However this is just my thoughts and the current accepted name is Triceratium harrisonianum.