Aulacodiscus allorgei from Kamishev, Russia. Single example on the slide. Mounted in Styrax and dated May 1969. Very nice and clear mountant. Prepared by RI Firth. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 91 images stacked in Zerene (Pmax) for the full stack. I also did a second stack so I could emphasize the processes as in the full stack their transparency allowed the features below them showed through and made the image look a little messy.
Aulacodiscus allorgei Chenevière, 1934. Original description: Chenevière, E. (1934). Sur un dépôt fossile marin à diatomées situé à Kamischev (Russie centrale). Bulletin de la Société Française de Microscopie, 3(3): 103-107, pls 5-8. Page 106, Plate 8, Figure 2.