Two examples of Stictodiscus parallelus (?), from Oamaru, New Zealand. I’ve put a question mark after the name and will come back to that in a minute. The two examples look to show a top view and bottom view. Prepared by Herbert William Hutton Darlaston. Olympus BHB microscope using 450nm LED light. 20x Nikon Plan Apo NA 0.65 objective. Olympus Aplanat Achromat condenser, brightfield lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera.
I’ve put a question mark after the name here as for me the name does not match the diatom. For example, the examples I have seen of S. parallelus are not circular. It is more likely Stictodiscus californicus var. areolata.