An example of a Stephanogonia sp. (I think probably S. actinoptychus) from the Atlantic city well site, USA. Single example on the slide. Dipping down away from the coverslip towards the upper left. No makers name. 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. 85 images stacked in Zerene (Pmax).
Stephanogonia actinoptychus (Ehrenberg) Van Heurck, 1882. Published in: Van Heurck, H. (1882). Synopsis des Diatomées de Belgique. Atlas. pp. pls LXXVIII-CXXXII [78-132 and supplementary pls 22 bis, 82bis, 83bis, 83ter, 95bis], tables genres. Anvers: Ducaju et Cie. Plate 83 ter, Figures 2-4. Homotypic synonyms: Pyxidicula actinoptychus Ehrenberg 1844, Mastogonia actinoptychus (Ehrenberg) Ehrenberg 1844. Fairly sure on this ID, however will leave it with a question mark for now.
The slide has very little information on it, however I did share another one by the same maker here. At the time of writing that I thought it might be by JA Long based on the handwriting, however that would be extremely tentative. Nice slides though.