Vanheurickia lewisiana, prepared by Watson and Sons Ltd. Single example on the slide. Mounted in Styrax. 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. 34 images stacked in Zerene (Pmax).
A bit on the name (and other names for this diatom).
Navicula lewisiana Greville 1863. Published in: Greville, R.K. (1863). Descriptions of new and rare Diatoms. Series VIII. Transactions of the Microscopical Society, New Series, London 11(3): 13-21, 1 pl. Page 15, Plate 1, Figure 7.
This name is currently regarded as a synonym of Frickea lewisiana (Greville) Heiden.
Frickea lewisiana (Greville) Heiden in A.W.F.Schmidt 1906. Published in: Schmidt, A.[W.F.] (1906). Atlas der Diatomaceen-kunde Series VI: Heft [66]. pp. pls 261-264. Bearbeitet von Dr. M. Schmidt. Leipzig: O.R. Reisland. Plate 264, Figure 1.
Homotypic Synonyms: Navicula lewisiana Greville 1863, Vanheurckia lewisiana (Greville) Brébisson 1869, Navicula rhomboides var. lewisiana (Greville) Dippel 1880, Frustulia lewisiana (Greville) De Toni 1891, Brebissonia lewisiana (Greville) Kuntze 1898.
It’s a brackish water species.