Podosira argus, single example on the slide. It has moved significantly and is now near the edge of the coverslip. No information on mountant or location (I have seen these before from Oamaru as well as other locations). Unknown maker. 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. 41 images stacked in Zerene (Pmax).
Podosira argus Grunow 1878. Published in: Grunow, A. (1878). Algen und Diatomaceen aus dem Kaspischen Meere. In: Naturwissenschaftliche Beiträge zur Kenntnis der Kaukasusländer, auf Grund seiner Sammelbeute. (Schneider, O. Eds), pp. 98-132. Dresden: Dresden Burdach. Page 132.
I recently acquired about 30 more slides by this maker to add to the ones I already had, so if you want to see others by them, search for AAAAA in the Search option at the top of the page, and I’ll include this in each of the pages for them.