Two examples of Triceratium majus from Oamaru, New Zealand. The larger one is broken, and with the rim upwards towards the coverslip (underside view). No makers name, but I this looks to be by William Allott Firth based on hand writing and style. Olympus BHB microscope using 450nm LED light. 20x Nikon Plan Apo NA 0.65 objective. Olympus Aplanat Achromat condenser, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 23 images stacked in Zerene (Pmax).
Triceratium majus (Grove & Sturt) Grove & Sturt 1888. Published in: Grunow, A. (1888). Referate. Grove, E. and Sturt, G. On a fossil marine diatomaceous deposit from Oamaru, Otago, New Zealand (Journal of the Quekett Microscopical Club. Ser. II Vol. III. No. 18 and No. 19.1887. Part III and appendix.). Botanisches Centralblatt 34(2/3): 34-41. Page 40.
Currently accepted name Entogoniopsis major as discussed in Jakub Witkowski, Patricia A. Sims, Nina I. Strelnikova & David M. Williams, “Entogoniopsis gen. nov. and Trilamina gen. nov. (Bacillariophyta): a survey of multipolar pseudocellate diatoms with internal costae, including comments on the genus Sheshukovia Gleser”, (Phytotaxa 209), 89 pp, available here.