An example of what I think is Navicula novaeseelandiae from Oamaru, New Zealand. Label says N. praetexta, but that doesn’t look right to me. Described as ‘scarce’. Single example on the slide mounted withe the rim upwards towards the coverslip (underside view). Prepared by Frederick Marshall. 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. 30 images stacked in Zerene (Pmax). 64µm long, 58µm wide as measured in ImageJ.
Navicula novaeseelandiae Hustedt, 1964. Published in: Hustedt, F. (1964). Die Kieselalgen Deutschlands, Österreichs und der Schweiz unter Berücksichtigung der übrigen Länder Europas sowie der angrenzenden Meeresgebiete. Bd. VII: Teil 3: Lieferung 3. In: Rabenhorst’s Kryptogamen Flora von Deutschland, Österreich und der Schweiz. (Anon. Eds), pp. 349-556. Leipzig: Akademische Verlagsgesellschaft m.b.h. Page 406, Figure 1486. This name is currently regarded as a synonym of Lyrella novaeseelandiae (Hustedt) D.G.Mann, 1990. Published in: 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. Page 672.
Also see: Desikachary, T.V. & Sreelatha, P.M. (1989). Oamaru diatoms. Bibliotheca Diatomologica 19: [1]-330, including 145 plates. Page 192, Plate 63, Figures 10,14.