Aulacodiscus oreganus (I think this is now spelt oregonus). Single example on the slide, mounted with the rim upwards towards the coverslip. No makers name or location. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, slightly oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 56 images stacked in Zerene (Pmax).
Aulacodiscus oregonus Harvey & Bailey 1853 (as ‘Oreganus‘). Published in: Harvey, W.H. & Bailey, J.W. (1853). New species of Diatomaceæ, collected by the United States Exploring Expedition, under the command of Capt. Wilkes, U.S.N. Proceedings of the Academy of Natural Sciences of Philadelphia 6(11): 430-431. Page 430.