Navicula praetexta from Santa Monica, California, USA. Single example on the slide. Prepared by WA Firth. Olympus BHB microscope using 450nm LED light. 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. 32 images stacked in Zerene (Pmax).
Navicula praetexta Ehrenberg 1841. Published in: Ehrenberg, [C.G.] (1840). [Characteristik von 274 neuen Arten von Infusorien]. Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich-Preussischen Akademie der Wissenschaften zu Berlin 1840: 197-219. Page 214. This name is currently regarded as a synonym of Lyrella praetexta (Ehrenberg) D.G.Mann. Source of synonymy: Round, F.E., Crawford, R.M. & Mann, D.G. (1990). The diatoms. Biology and morphology of the genera. pp. [i-ix], 1-747. Cambridge: Cambridge University Press. I’m assuming the original way of writing this was N. prætexta.