Three examples of Campylodiscus spiralis prepared by Watson and Sons Ltd. The pigment from the black ring around the diatoms has bled across the slide. Olympus BHB microscope using 450nm LED light. As well as the group, I imaged one using the 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. 106 images stacked in Zerene (Pmax).
Campylodiscus spiralis (Kützing) R.Gutwinski 1891. Published in: Gutwinski, R. (1891). Flora glonów okolic Lwowa – Flora algarum agri Leopoliensis. Sprawozdania Komisji fizjograficznej Akademii Umiejetnosci, Kraków 27: 1-124. Page 102. This name is currently regarded as a synonym of Iconella spiralis (Kützing) E.C.Ruck & T.Nakov 2016. Published in: Ruck, E.C., Nakov, T., Alverson, A.J. & Theriot, E.C. (2016). Nomenclatural transfers associated with the phylogenetic reclassification of the Surirellales and Rhopalodiales. Notulae Algarum 10: 1-4. Page 2.
Also see: Campylodiscus spiralis (Kützing) W.Smith 1851. Published in: Smith, W. (1851). Notes on the Diatomaceae, with descriptions of British species included in the genera Campylodiscus, Surirella and Cymatopleura. Annals and Magazine of Natural History, series 2 7: 1-14, pls I-III. Page 6, Plate 1, Figure 2a.
I think this is also referred to as Surirella spiralis Kützing 1844. Published in: Kützing, F.T. (1844). Die Kieselschaligen Bacillarien oder Diatomeen. pp. [i-vii], [1]-152, pls 1-30. Nordhausen: zu finden bei W. Köhne. Page 60, Plate 3, Figure 64.