Actinoptychus heliopelta (with 14 sectors) from Maryland, USA. Single example on the slide. Yellowed mountant with bubbles in it. Prepared by JA Long. 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. 34 images stacked in Zerene (Pmax). The final image is relatively low resolution given the use of the 20x objective, but this is a big diatom (approx. 271µm diameter).
Actinoptychus heliopelta Grunow 1883. Published in: Van Heurck, H. (1882). Synopsis des Diatomées de Belgique. Atlas. pp. pls LXXVIII-CXXXII [78-132 and supplementary pls 22 bis, 82bis, 83bis, 83ter, 95bis], tables genres. Anvers: Ducaju et Cie. Plate 123, Figure 3.