Actinoptychus heterostrophus (spelt as heterotrophus on the slide) from Simbirsk, Russia. Two examples on the slide. There is no makers name on the label however it is very similar to slides by WA Firth, although Barbour brothers ones are also very similar. For now I’ve put it down as WA Firth but with a question mark. Dated May 1886. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.40 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, very oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Stacks prepared in Zerene (Pmax).