An example of what I think is Monopsia marginata from Singil[iewsky, Russia]. Spelt Monopsis on the label. Single diatom on the slide. Described as ‘v. faint valve’. No details on the mountant. Some issues with the mountant and adhesive to the coverslip. Unknown maker. Olympus BHB microscope using 450nm LED light. 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. 66 images stacked in Zerene (Pmax).
Monopsia marginata 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 106, Plate 8, Figure 1. This could be M. marginata, based on the description in “The diatom genus Monopsia Grove and Sturt: morphology, classification and a note on the relevance of fossil characters”, Pat A. Sims & David M. Williams, Nova Hedwigia, 2021, Beiheft 151, p. 249–259. However there is no image of this species to compare with. As I haven’t found an image of one to compare this with I will leave it with a question mark for now.
I have a second slide by this maker, also described as M. marginata from Camische [Kamischev, Russia], however I think that is incorrect and that it is Monopsia mammosa.
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.