Rattrayella sp. (I am fairly sure this is Rattrayella rattrayi) from Singilevo, USSR. Single example on the slide. Mounted in Naphrax and dated 25/7/[19]74. Prepared by Richard Gosden. 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. 57 images stacked in Zerene (Pmax). High contrast (Naphrax) and this has resulted in a very dark edge to the diatom.
Rattrayella rattrayi (Pantocsek) P.A.Sims 2006. Published in: Sims, P.A. (2006). A revision of the genus Rattrayella De-Toni including a discussion on related genera. Diatom Research 21(1): 125-158. Page 133, Figures 25-38.