Aulacodiscus affinis from from Sendai (written as Sandai on the label), Japan. Single example on the slide, dipping downwards towards the upper left. 13 processes. Prepared by Laurence Miles. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. 11mm removed from tube the camera to increase the field of view. Monochrome converted Nikon d850 camera. 126 images stacked in Zerene (Pmax).
Aulacodiscus affinis Grunow 1876. Published in: Schmidt, A.[W.F.] (1876). Atlas der Diatomaceen-kunde. Series I: Heft 9. pp. pls. 33-36. Aschersleben: Verlag von Ernst Schlegel. Plate 34, Figures 9,10. Looks to be a good visual match.