An Aulacodiscus sp. (I think this could be A. pellucidus) from Hong Kong. Single example on the slide. 7 processes. Cover gauge 0.004” (0.10mm) – thin coverslip. Dated 1893. Prepared by William Allott Firth. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 50 images stacked in Zerene (Pmax).
Aulacodiscus pellucidus Greville 1864. Published in: Greville, R.K. (1864). Descriptions of new and rare Diatoms. Series XI. Transactions of the Microscopical Society, New Series, London 12: 8-14, pls I, II. Page 12, Plate I [1], Figure 5. This is a tentative ID, but looks reasonable. I have another example on the site, which is on a named slide.