A strew slide from Kettleman Hills (spelt Keffleman on the slide), under sandstone. This is a site in California, USA. Prepared by Bernard Hartley. Mounted in Aroclor and dated April 1975.
With regards to naming for the diatoms on this slide I have mainly used: Pliocene diatoms from the Kettleman Hills, California, Professional Paper 189-C. By: K. E. Lohman. https://doi.org/10.3133/pp189C. Based on there being plenty of Hyalodiscus schmidtii on the slide I think this is likely site 1053 in the paper. Due to the height of the ring around the coverslip, I was prevented from using the 63x Leitz Pl Apo objective I prefer, and instead used the 40x Leitz Pl Apo NA 1.00 one.
Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo NA 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, brightfield lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Image stacks prepared in Zerene (Pmax).
Hyalodiscus schmidtii. This could be an aberrant example given the part in the central region. Viewed from the underside. 84 images stacked.
Triceratium uncinatum. Underside view. This is shown in Schmidt’s Atlas, Plate 94, Fig 4. The description for this states, “Westküste v. Centralamerica. vielleicht, wie Grunow vermuthet, eine Hydrosera.” which translates (roughly) as “West coast of Central America. Perhaps as Grunow suspected a Hydrosera.”. I too initially thought Hydrosera when I saw this, so perhaps it is rather than a Triceratium. 33 images stacked.
Melosira undulata. I have thoughts about this one. In the article mentioned above it states that Melosira undulata var. normanii (also spelt normannii) is present at this site. However to me it looks more like Melosira undulata (rather than the var. normanii variant). Examples of both of these can be seen at the following links – https://diatoms.org/species/melosira_undulata/guide, https://diatoms.org/species/melosira_normannii. 13 images stacked.
Cymbella sp.. Not sure which species, but Cymbella mexicana var. gracilis seems a good match). 17 images stacked.
Overall an interesting slide with some unusual species present.