An Actinoptychus sp. (with boliviensis added on to the label) from Palos Verdes, California, USA. I’ll come back to the name in a minute. Single example on the slide. Fossil marine material. Mounted in Styrax and dated July 1945. No makers name. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo NA 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 93 images stacked in Zerene (Pmax). I used slightly less sharpening that usual for this image, as there was a lot of well resolved detail already in the stack.
Back to the name. Actinoptychus boliviensis Janisch 1874. Published in: Schmidt, A.[W.F.] (1874). Atlas der Diatomaceenkunde. Series I, Heft 1. pp. pls 1-4. Aschersleben: [Verlag von Ernst Schlegel]. Plate 1, Figure 23. However, am I convinced by this name? Not a species I associate strongly with Palos Verdes, and it doesn’t look quite right to me. However Meakin thought there were some there – https://diatomimaging.com/actinoptychus-boliviensis-samuel-meakin/
I think it’s more like Actinoptychus stella var. clevei (A.W.F.Schmidt) W.W.Wornardt 1967. Published in: Wornardt, W.W., Jr (1967). Miocene and Pliocene marine diatoms from California. Occasional Papers of the California Academy of Science 63: [1]-108. Page 48, Figure 78. Basionym; Actinoptychus clevei A.W.F.Schmidt 1886. Published in: Schmidt, A.[W.F.] (1886). Atlas der Diatomaceen-kunde Series III: Heft 23. pp. pls 89-92. Aschersleben: Commissions-Verlag von Ludwig Siever’s Buchhandlung. Plate 91, Figure 1.
For now I will leave it as described but with a question mark.