Entogonia sp.. Location probably Szirák (more on this in a minute). Single example, underside facing 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. 31 images stacked in Zerene (Pmax). Issues with the mountant above the diatom, and the final image was low contrast.
There is a good review of this genus in: Holmes, R.W. & Brigger, A.L. (1979). The marine fossil diatom genus Entogonia Greville – A review. Bacillaria 2: 155-214. Looking through this, I think this is likely Entogonia hungarica (Plate 8, Figs 66-72). As for the location, the reference above gives Szurdokpüspöki mentioned as being a likely location for the Hungary site (that of Castel being unknown). Szirák is only a few km’s West of Szurdokpüspöki, so this could be correct (and there is a Castle – Kastel – in Szirák, although this idea that this is ‘the’ site of Castel is purely speculation on my behalf).
I recently acquired about 60 slides by this maker, 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.