Coscinodiscus sp. from Tamatave (Madagascar). Single example on the slide. Mounted in Styrax. Prepared by Samuel Henry Meakin. 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. 32 images stacked in Zerene (Pmax).
As for species, I’m not really sure. Looks a bit like Coscinodiscus decrescens from Oamaru (Desikachary, T.V. & Sreelatha, P.M. (1989). Oamaru diatoms. Bibliotheca Diatomologica 19: [1]-330, including 145 plates. Pages 125, Plate 53, Figures 2,3). Or maybe Coscinodiscus bulliens (but I am less convinced by this one).