Coscinodiscus symmetricus (with a question mark after it, not sure why as this looks like C. symmetricus) from Springfield, Barbados. Single example on the slide. ‘Cover guag’ (presumably Coverslip gauge/thickness) 0.0035” (0.14mm). Dated 1893 (maybe December 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. 71 images stacked in Zerene (Pmax). I had expected this to be fairly flat, but it was actually quite ‘undulaty’ radially out from the middle.
Coscinodiscus symmetricus Greville 1861. Published in: Greville, R.K. (1861). Descriptions of new and rare Diatoms. Series II. Transactions of the Microscopical Society, New Series, London 9: 67-73, pl. VIII. Page 68, Plate 8, Figure 2.