Aulacodiscus scaber (4 processes). Single example on the slide mounted with the rim upwards towards the coverslip (underside view). Ring around the diatom has broken down and some has gone over the diatom. No makers name or location. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo NA 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 84 images Pmax.
Aulacodiscus scaber 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.
Also see: Mary A. Tiffany (2008), Valve Development in Aulacodiscus, Diatom Research, 23:1, 185-212, DOI: 10.1080/0269249X.2008.9705746