Triceratium megastomum from South America. 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 188?. 4 examples on the slide in a cross arrangement. There were protuberances on vertices of the polygons, but these were lost in the image stack due to stronger more define features below, however they can be seen by looking at the individual frames from different depths. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.40 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 26 images stacked in Zerene (Pmax).