Bit of a troubled slide this one. Yellowed mountant, coverslip partially come away and numerous cracks, extensive mold in the mountant, warped/bowed slide. An arrangement of Navicula rhomboides from Saco, USA (maybe Saco Pond, a small spring-fed waterbody nestled in the White Mountains of New Hampshire, see – FW Lewis. (1863). On Some New and Singular Intermediate Forms of Diatomaceæ. Proceedings of the Academy of Natural Sciences of Philadelphia, 15, 336–346. http://www.jstor.org/stable/4059821). No makers name, but prepared by Laurence Hardman. Olympus BHB microscope using 450nm LED light. As well as the wider field of view, I imaged one using the 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. 22 images stacked in Zerene (Pmax).
Navicula rhomboides Ehrenberg 1843: 419 (131); pl. 3/1, fig. 15. Published in: Ehrenberg, C.G. (1843). Verbreitung und Einfluss des mikroskopischen Lebens in Süd- und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1841: [291]–445 + [1, Berichtigungen], pls 1–4. This name is currently regarded as a synonym of Frustulia rhomboides (Ehrenberg) De Toni 1891: 277. Published in: De Toni, G.B. (1891). Sylloge algarum omnium hucusque cognitarum. Vol. II. Sylloge Bacillariearum. Sectio I. Rhaphideae. pp. [i-iii]. [i]-cxxxii, 1-490. Patavii [Padua]: Sumptibus auctoris.