An arrangement of two Navicula zanzibarica from Delagoa Bay (now Maputo Bay, south east coast of Mozambique). One viewed from above (left), one underside view with the rim to the coverslip (right). Prepared 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. 41 images stacked in Zerene (Pmax). Couldn’t get close enough with the 63x Leitz to get a higher resolution image.
Schmidt’s Atlas Plate 2, Figures 3 and 3a. I am guessing this is the same as Navicula zanzibarica var. zanzibarica Greville, 1866. Original description: Greville, R.K. (1866). Descriptions of new and rare Diatoms. Series XX. Transactions of the Microscopical Society, New Series, London, 14: 121-130, pls XI & XII. Page 129, Plate 12, Figure 22. This name is currently regarded as a synonym of Lyrella zanzibarica (Greville) D.G.Mann.
I have another partial example of this here where it also shows the pages from the Greville article.