Interesting slide this one. It is labelled as Coscinodiscus reniform from Mount Hillaby, Barbados. I’ll come back to the name at the end. Mounted in Styrax. Prepared by HRS Williams. Olympus BHB microscope using 450nm LED light. Image of the single diatom with a 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. 23 images stacked in Zerene (Pmax).
Back to the name. There are 3 diatoms which looks to be the same in between 2 disc shaped ones. The middle 3 are egg shaped. The name Coscinodiscus reniform to me implies ‘kidney shaped’ (there is a Coscinodiscus reniformis which is kidney shaped). However these are distinctly egg shaped rather than kidney shaped, so I don’t think they warrant the ‘reniform’ description. Looking a the high magnification image they look more to be Cestodiscus of some type based on the overall structure, maybe a variant of Cestodiscus ovalis? If anyone has seen anything like this please let me know as so far I have not been able to find any similar diatoms.