Aulacodiscus superbus from Joe’s River, Barbados (more on the name later). Single example on the slide. Prepared by Samuel Henry Meakin. Mounted in Styrax and dated December 1933. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, brightfield lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 62 images stacked in Zerene (Pmax).
Back to the name. The slide is labelled Aulacodiscus crater v. superbus, with crater struck through. I did look up A. crater, and it is mentioned in BRUN, J. & TEMPERE, J. (1889) [1890]. Diatomees fossiles du Japon. Especes marines et nouvelles des calcaires argileux de Senai and de Yedo. Mémoires de la Société de physique et d’histoire naturelle de Genève, t. 30, no. 9 pls. I can see why he crossed this out though. Next to look up was A. superbus. This is written about in Kitton, F. (1873). A description of some new species of Diatomaceae. Monthly Microscopical Journal, London, 10: 205-207, pl. 38 page(s): p. 205; pl. 38, fig. 1. This turned out to be a good fit, and I have included a screen grab from the reference to show this. I am happy with the name of Aulacodiscus superbus for this one.
A beautiful diatom. Yes, this example is broken which is obviously a shame. However I doubt I’ll ever see another one.