An Entogonia sp. from Barbadoes [sic]. Single example on the slide, dipping down slightly towards the bottom left. Mounted in Naphrax and dated 1950. Prepared by Horace George Barber. Olympus BHB microscope using 450nm LED light. 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. 61 images stacked in Zerene (Pmax).
Ok, the name. The slide simply has this as Entogonia. 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 the images in this, I am leaning towards this being either Entogonia formosa, or Entogonia formosa var. protuberans. However I acknowledge that this is a tentative identification.