Triceratium robustum. Single example on the slide. No makers name, but I understand this was prepared by Frederick Marshall. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, slightly oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 74 images stacked in Zerene (Pmax).
Described in: Greville, R. K. (1861). Descriptions of new and rare Diatoms. Series II. Transactions of the Microscopical Society, New Series, London. 9: 67-73. page(s): p. 71; pl. 8, fig. 15