Slide labelled Surirella fastuosa (although I think this is Surirella collare and will come back to this in a minute). Single example on the slide, from Tamatave (now Toamasina, Madagascar). Cracked coverslip. Prepared by Henry James Baker. 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. 45 images stacked in Zerene (Pmax).
Back to the name. The name S. fastuosa didn’t look right to me for this one. Mainly because S. fastuosa has a feature resembling two rows of lines running near the centre along its length. I went through Schmidt’s Atlas and the best match was Surirella collare (Plate 4, Figure 14 and Plate 19, Figure 7 and Plate 365, Figure 3 – this one is a very good match, and came from Komoren, which is the Comoros Islands just off the north west of Madagascar). So I think this is S. collare.
Interestingly there is a Surirella fastuosa var. collare (A.W.F.Schmidt) Cleve 1901: Published in: Cleve, P.T. (1901). Plankton from the Indian Ocean and the Malay Archipelago. Kungliga Svenska Vetenskaps-Akademiens Handlingar, N.F. 35(5): 1-58, 8 pls [I-VIII]. Page 30. This name is currently regarded as a synonym of Surirella collare A.W.F.Schmidt. So, it looks like this was likely considered S. fastuosa (at least a variant of) perhaps when the slide was made. The joys of diatom naming. To me it looks like a Campylodiscus, but that is for another day.