An arrangement of three Surirella engleri var. from Warri, South Nigeria. No makers name, but I think this is by JA Long. 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. 30 images stacked in Zerene (Pmax). I couldn’t get close enough with the 63x Leitz objective so resolution is limited. I can just about see the striae, especially when looking at a single frame from the stack and boosting the contrast a bit. This would have been more visible with the 63x NA 1.4 objective, but c’est la vie.
Surirella engleri O.Müller 1904. Published in: Müller, O. (1904). VII. Bacillariaceen aus dem Nyassalande un einigen benachbarten gebieten. Botanische Jahrbücher für Systematik Pflanzengeschichte und Pflanzengeographie 34(1): 9-38, pls I, II. Page 28, Plate I [1], Figure 4. This name is currently regarded as a synonym of Iconella engleri (O.Müller) C.Cocquyt & R.Jahn. Source of synonymy: Cocquyt, C., & Jahn, R. (2007). Surirella engleri O. Müller – A study of its original infraspecific types, variability and distribution. Diatom Research, 22(1), 1–16. https://doi.org/10.1080/0269249X.2007.9705691