An arrangement of Navicula firma from Aberdeenshire, Scotland. I think this was made by WA Firth (probably, not named but similar style) but am not 100%. Olympus BHB microscope using 450nm LED light. 10x Nikon Plan Apo NA 0.45 objective. Olympus Aplanat Achromat condenser, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 17 images stacked in Zerene (Pmax).
Navicula firma 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 92, Plate 21, Figure 10. This name is currently regarded as a synonym of Neidium firmum (Kützing) Pfitzer. Source of Synonymy: Pfitzer, E. (1871). Untersuchungen über Bau und Entwicklung der Bacillariaceen (Diatomaceen). In: Botanische Abhandlungen aus dem Gebiet der Morphologie und Physiologie Bd 2. pp. [i]-vi, [1]-189, plus 6 pls. Bonn: bei Adolph Marcus.