Actinoptychus boliviensis from Palos Verdes, California, USA. Prepared by Samuel Meakin. Mounted in Sirax, dated August 1943. ‘Sch at 1/23’ refers to Schmidt’s Atlas der Diatomaceen-Kunde, plate 1, fig. 23 (available here). Olympus BHB microscope using 450nm LED light. 20x Nikon Plan Apo NA 0.65 objective. Olympus Aplanat Achromat condenser, oil immersion, slightly oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 20 images stacked in Zerene (Pmax).