An Auliscus sp. from San Redondo, California, USA. More on a name in a minute. Single example on the slide. Prepared by Laurence Miles. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 45 images stacked in Zerene (Pmax). Coverslip ring was too tall to allow use of the 63x Leitz unfortunately.
Back to the name. I think this is Auliscus stöckhardtii (there is another example of this here). I’m guessing this is the same as Auliscus stoeckhardtii var. stoeckhardtii Janisch, 1861. Original description: Janisch, C. (1861). Zur Charakteristik des Guano’s von verschieden Fundorten. Abhandlungen der Schlesischen Gesellschaft für vaterlandische Cultur. Abtheilung für Naturwissenschaften und Medicin. Breslau. 150-164. Page 163, Plate 1, Figure 4. ‘Stöckhardtii’ with the umlaut is presumably the original spelling.