Aulacodiscus brownei (spelt brownii on the slide) from Monterey, California, USA. Single example on the slide. Prepared by Ernest Hinton. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 43 images stacked in Zerene (Pmax). Unfortunately due to the coverslip ring, the 63x objective couldn’t image the base of the diatom, to most of the rim is out of focus. I did another image with the 40x Leitz Pl Apo NA 1.00 oil immersion objective, using oblique lighting, 54 images stacked in Zerene (Pmax). This is lightly lower resolution, but all in focus.
Aulacodiscus brownei Norman ex Ralfs, 1861. Published in: Pritchard, A. (1861). A history of infusoria, including the Desmidiaceae and Diatomaceae, British and foreign. Fourth edition enlarged and revised by J. T. Arlidge, M.B., B.A. Lond.; W. Archer, Esq.; J. Ralfs, M.R.C.S.L.; W. C. Williamson, Esq., F.R.S., and the author. pp. [1]-xii, [1]-968, 40 pls [I-XV]. London: Whittaker and Co.. Page 844 (as ‘A. Browneii (Norman, MS.)’)
Syntype localities: “Shell-cleanings, California and elsewhere in the Pacific. Fossil, Monterey stone.” ; (Pritchard 1861: 844-5). Presumably this one is fossil material then.