An arrangement of three Aulacodiscus pugnalus (also spelt pugnalis) from Moreno Shale, Y Canyon, California, USA. W.D.F. #1388 Mat. Mounted in Sty.aro. (presumably Styrax, Aroclor), and dated August 1968. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo NA 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, slightly oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 53 images stacked in Zerene (Pmax).
This diatom is referred to in Hanna, G.D. (1927). Cretaceous diatoms from California. Occasional Papers of the California Academy of Sciences 13: 5-[49]. Pages 14,15, Plate 1, Figures 6,7. In this it is spelt ‘pungalus‘ a couple of times as well as ‘pugnalis‘. In the WoRMS database it states that the accepted name is A. pugnalus (see here). For another example on this site, and more on the name, see here.