Navicula praetexta from Palos Verdes, Malaga Cave, California, USA. Single example on the slide mounted with the rim upwards (underside view). It has moved from the middle of the circle. Mounted in Styrax. No makers name but based on the style it may be by Wallace Frederick Reeve. Olympus BHB microscope using 450nm LED light. 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. 68 images Pmax. Underside view, rim upwards.
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.