Actinoptychus sp. from Hayti [Haiti]. Maybe A. senarius, but I’m not sure. Single example on the slide. The diatom is a dark orange in colour, not sure if this from mineral content, or if it has picked up colouration from the ring around it somehow. Makes it very dark when imaged using 450nm LED light. Unknown maker. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo 1.00 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).
I recently acquired about 60 slides by this maker, so if you want to see others by them, search for AAAAA in the Search option at the top of the page, and I’ll include this in each of the pages for them.