Two examples of Aulacodiscus petersii from Panama shells (5 and 6 processes). Prepared by Laurence Miles. Olympus BHB microscope using 450nm LED light. As well as the arrangement, I imaged the 6 process one using 63x Leitz Pl Apo NA 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 97 images stacked in Zerene (Pmax). There was a strong irregular dot pattern which shows up in a partial stack but is lost in the full stack. These ’dots’ appear higher up, closer to the coverslip, than the main ‘corn-cob’ texture of the diatom.
Aulacodiscus petersii Ehrenberg 1845. Published in: Ehrenberg, C.G. (1845). [Novorum generum et specierum brevis definitio. Zusätze zu seinen letzten Mittheilung über die mikroskopischen Lebensformen von Portugall und Spanien, Süd-Afrika, Hinter-Indien, Japan und Kurdistan, und legte die folgenden Diagnosen u.s.w.]. Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich-Preussischen Akademie der Wissenschaften zu Berlin 1845: 355-377. Page 361.
Also seen spelt petersi. 6 processes seems to be unusual.