Arachnoidiscus antiquus from Moreno shale, California. Fossil marine. Single example on the slide. Cracked coverslip, and the diatom is mounted quite deeply (and slightly tilted). Not named, but I understand this was prepared by Wallace Frederick Reeve. Mounted in Sirax and dated October 1947. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oblique lighting, oil immersion. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 33 images stacked in Zerene (Pmax).
Original description: Barker, J.W. & Meakin, S.H. (1945). New and rare diatoms. Journal of the Quekett Microscopical Club, Series 4, 2(1): 18-22, pl. 3-4. Page 18, Plate 3, Figure 2.