Campylodiscus clypeus from Paoha Island, Mono Lake, California, USA. Single example on the slide. C.A.S. (California Academy of Sciences) 34134A. Mounted in Naphrax and dated January 1970. Prepared by ECP Bone. 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. 111 images stacked in Zerene (Pmax). Couldn’t get close enough with the 63x Leitz Pl Apo, so resolution is limited.
Campylodiscus clypeus (Ehrenberg) Ehrenberg ex Kützing 1844. Published in: Kützing, F.T. (1844). Die Kieselschaligen Bacillarien oder Diatomeen. pp. [i-vii], [1]-152, pls 1-30. Nordhausen: zu finden bei W. Köhne. Page 59.
Also see: Aloisie Poulícbreve ková, Regine Jahn, Campylodiscus clypeus (Ehrenberg) Ehrenberg ex Kutzing: Typification, morphology and distribution, Diatom Research 2007, 22(1): 135-146.