Coscinodiscus symmetricus from Newcastle, Barbados. Single example on the slide, mounted with the underside facing upwards (rim towards the coverslip). Described as ‘rare’ on the slide. Prepared by WA Firth. 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. 53 images stacked in Zerene (Pmax).
Some of the descriptions;
Schmidt’s Atlas, Plate 57, Figs 25-27.
John Rattray (1890). A Revision of the Genus Coscinodiscus and some Allied Genera. Proceedings of the Royal Society of Edinburgh, 16, pp 449-692 doi:10.1017/S0370164600006489. Page 490.
Greville, R.K. (1861), Descriptions of New and Rare Diatoms. Series II. Transactions of The Microscopical Society & Journal, 9: 67-73. https://doi.org/10.1111/j.1365-2818.1861.tb06243.x. Page 68, Plate 8 (VIII), Figure 2. Screen shots from here are shown above.