Cocconeis sp. (rare) from California, USA. Single example on the slide. Mounted in Sirax and dated May 1941. Prepared by Samuel Henry Meakin. 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. 37 images stacked in Zerene (Pmax).
No species is given, but there is a reference to Schmidt’s Atlas Plate 191, Figure 38 on the slide, and this looks to be a good match for that (screenshot given for comparison). According to Schmidt’s Atlas, this was from ‘Santa Monica, fragile’. Also see Plate 22. Marine diatoms from the Galapagos Islands, Figure 27, https://pubs.usgs.gov/of/2012/1163/pages/Plates/22_Galapagos.pdf