Slide labelled as Triceratium exornatum (more on this in a minute). Single example on the slide, mounted with the rim towards the coverslip (underside view). No details on location or mountant. 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. 39 images stacked in Zerene (Pmax).
Back to the name. This doesn’t look like T. exornatum according to the image in Schmidt’s Atlas (Plate 112, Figures 1,2). However I have another example of a slide labelled as T. exornatum on this site, which looks pretty much like this one. Very odd.
However looking further I came across Triceratium exornatum Greville 1865. Published in: Greville, R.K. (1865). Descriptions of new and rare diatoms. Series XIV. Transactions of the Microscopical Society, New Series, London 13: 1-10, 2 pls [I, II]. Page 9, Plate II [2], Figure 25. This name is currently regarded as a synonym of Sheshukovia exornata (Greville) Glezer 1984. Published in: Glezer, Z.I. (1984). Znachenie issledovanij po sistematike diatomovych vodoroslej dlia biostrtigrafii i paleogeographii [The importance of research about systematics of diatom algae for biostratigraphy and paleogeography]. Ezhegodnik Vsesoyuznogo Paleontologicheskogo Obshchestva 27: 284-298, 1 figure, 1 table. [in Russian]. Page 293.
The example in Greville 1865 does look more similar to this one but this has more concave sides. However in Greville 1865 there is also Triceratium insignis which to me looks to be a better match to this and other example on this site. Triceratium insigne f. insignis Greville, 1861. Original description: Greville, R. K. (1861). Descriptions of new and rare Diatoms. Series III. Transactions of the Microscopical Society, New Series, London. 9: 73-77. Page 75, Plate 9, Figure 5.
Where does this leave me? For now I am going to leave it as Triceratium sp. but with a question mark after it. I would appreciate any comments about this name.
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.