Aulacodiscus mölleri from New Jersey, USA. Single example on the slide. No makers name. Cracked coverslip. Handwriting looks a bit like WA Firth, but I have not seen one of his with a label like that before, so will leave it as ‘unknown maker’ for now. 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. 79 images stacked in Zerene (Pmax).
Aulacodiscus moelleri Grunow 1876. Published in: Schmidt, A., Schmitz, M., Fricke, F., Müller, O., Heiden, H. & Hustedt, F. (1874-1959). Atlas der Diatomaceen-Kunde. 4 Bands, pls. 1-480. . Leipzig. Plate 33, Figure 14. This name is currently regarded as a synonym of Aulacodiscus margaritaceus var. moelleri (Grunow) Rattray 1888. Published in: Rattray, J. (1888). A revision of the genus Aulacodiscus Ehrb. Journal of the Royal Microscopical Society 8(3): 337-382, 3 pls [V-VII]. Page 352. Note the ‘oe’ is used in place of ‘ö’.