Triceratium bullatum from Papakaio U, Oamaru, New Zealand. Single example on the slide. Mounted in Styrax, and dated 15/4/[19]39. No makers name, but I think this is by WF Reeve (but will leave it with a question mark for now). Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 85 images stacked in Zerene (Pmax). Reverse order stack from bottom to top. Dipping down towards the bottom right.
Triceratium bullatum Grove, 1890. Published in: Bergon, P., Cleve, P.T., Grove, E. & Tempère, J. (1890). Diatomées rares ou nouvelles. Le Diatomiste 1(1): 2-7. Page 5, Plate I [1], Figure 3. Also see Desikachary, T.V. & Sreelatha, P.M. (1989). Oamaru diatoms. Bibliotheca Diatomologica 19: [1]-330, including 145 plates.