An arrangement of Aulacodiscus, Cerataulus and Kittonia from Russia. Unknown maker. Olympus BHB microscope using 450nm LED light. I selected a couple of them for imaging at higher resolution with a 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Image stacks prepared in Zerene (Pmax).
Cerataulus deflandrei Cheneviere, 1934. Published in: 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 105, Plate 3(7), Figure 3.
Aulacodiscus lemardeleyi seems like a good visual match. Fragment. Underside view. Aulacodiscus lemardeleyi Chenevière 1934. Published in: 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 105, Plate 5, Figure 2.
I recently acquired about 30 more slides by this maker to add to the ones I already had, so if you want to see others by them, search for AAAAA in the Search option at the top of the page, and I’ll include this in each of the pages for them.