Triceratium sp. from Newcastle, Barbados. Labelled as T. harrisonianum, but I am not convinced by this, more in a minute. Single example on the slide, with slight damage. Prepared by Laurence Miles. Label on the rear of the slide as well. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.6 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 45 images stacked in Zerene (Pmax). The slide is warped/twisted, which made imaging a challenge.
Back to the name: Triceratium harrisonianum G.Norman & 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 9, Figure 9. This name is currently regarded as a synonym of Stictodiscus harrisonianus (G.Norman & Greville) Castracane. 1886. Published in: Castracane, [C.A.] F. (1886). Report on the Diatomaceae collected by H.M.S. Challenger during the years 1873-76. In: Report on the Scientific Results of the Voyage of H.M.S. Challenger during the years 1873-76. Botany. Vol. II. (Murray, J. Eds), pp. [1]-178. Page 116. Also see Schmidt’s Atlas Plate 448, Figures 6-11.
However looking at the images in Schmidt’s Atlas, they don’t really look like this. To me the dot pattern and surface texture makes it look to be a triangle form of a couple of potential species;
Stictodiscus truani var. trigona. Schmidt’s Atlas Plate 446, Figure 4. Good match and does come from Barbados.
Stictodiscus johnsonianus f. trigona. Schmidt’s Atlas Plate 442, Figures 10-12. Probably more leaning towards this one.
I am lacking a good image of a known T. harrisonianum to make a comparison with (I do have another one on this site, but again, I have concerns). If I become convinced, I will come back and update this.