An arrangement of Triceratium obscurum from the Cambridge Estate, Barbados. No makers name, but based on the style, prepared by Laurence Hardman. For the single diatom image, 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, slightly oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 17 images stacked in Zerene (Pmax).
Triceratium obscurum Greville 1861. Published in: Greville, R.K. (1861). Descriptions of new and rare Diatoms. Series III. Transactions of the Microscopical Society, New Series, London 9: 73-77, pl. IX. Page 76, Plate IX, Figure 8.
This name is currently regarded as a synonym of Azpeitia obscura (Greville) P.A.Sims. Azpeitia obscura (Greville) P.A.Sims 1988 (as ‘Azpeitia obscurum‘) published in: Williams, D.M. (1988). An illustrated catalogue of the type specimens in the Greville diatom herbarium. Bulletin of the British Museum (Natural History), Botany 18(1): 1-148, incl. 74 pls. Page 71, Plate 66, Figure 3.
Interesting feature. As far as I can tell nearly all of these have one apex of the triangle which looks different to the other 2, and is very reminiscent of Triceratium in form (the top apex in the image above).