Cerataulus turgidus from Santa Monica. Single example on the slide. Slide just labelled as Cerataulus, but I am fairly sure this is C. turgidus. No name on the slide but the style is that of Frederick Marshall. 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. 90 images stacked in Zerene (Pmax). This is a thick diatom and I couldn’t use the 63x Leitz Pl Apo objective due to this.