Three examples of Navicula spectabilis var. vavauensis (more on this in a minute) from Vavau, Friendly Is. (from Google AI….. Vavaʻu is a northern island group of Tonga. The name “Friendly Islands” originated with Captain Cook, who was warmly received by the local people during his visits centuries ago, and this welcoming spirit remains a characteristic of the islands.). Prepared by William Allott Firth. 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. 26 images stacked in Zerene (Pmax).
Back to the name. The label says ‘New, very rare’. I think it also says ‘June 1923’, which is very faint at the side of the label. If this is correct, it would be just before his death in July 1923. I can find no mention of this variation either online or in the books/articles I have access to. It certainly does look like Navicula spectabilis (now Lyrella spectabilis). Is this a new variant? Firth presumably thought so, but so far I cannot find mention of it. If you know of a reference for this please let me know.