Aulacodiscus reticulatus from Le Gard, France. Single example on the slide. Quite tilted (as is the coverslip as well). No makers name, but I am fairly sure this is by Sydney Chaffers (or perhaps the Manchester Microscopical Society). Olympus BHB microscope using 450nm LED light. 20x Nikon Plan Apo NA 0.65 objective. Olympus Aplanat Achromat condenser, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 61 images stacked in Zerene (Pmax).
Aulacodiscus reticulatus Pantocsek 1886. Published in: Pantocsek, J. (1886). Beiträge zur Kenntnis der Fossilen Bacillarien Ungarns. I. Theil Marine Bacillarien. pp. 1-74, 30 pls. Nagy-Tapolcsány: Buchdrucherei von Julius Platzko. Page 60, Plate I, Figure 1.