A puzzling slide. The label(s) are confusing and seem to indicate a Pseudauliscus species (more later on this). Location, again, trying to decipher the handwriting, but could be Cambridge, Barbados (which would tie in as a location that this maker has produced a number of slides from). Single example on the slide. Unknown maker. 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. 33 images stacked in Zerene (Pmax).
Ok names. The slide has Pseudauliscus ambiguus var. major written in ink, and then ralfsii (perhaps meaning ralfsianus) in pencil. Here’s what I’ve been able to find for these.
P. ambiguus var. major. Reference: Rattray, J. (1888). A revision of the genus Auliscus Ehrenberg and of some allied genera. Journal of the Royal Microscopical Society 1888: 861-920, 5 pls [XII-XVI]. Pages 900-901. Plate XV, Fig 1.
Pseudauliscus ambiguus. Reference (as Auliscus ambiguus): Greville, R.K. (1863). Descriptions of new and rare Diatoms. Series IX. Transactions of the Microscopical Society, New Series, London, 11(3): 63-76, pls IV & V. Page 74; plate 5, fig. 23.
Pseudauliscus ralfsianus. Reference: Rattray, J. (1888). A revision of the genus Auliscus Ehrenberg and of some allied genera. Journal of the Royal Microscopical Society 1888: 861-920, 5 pls [XII-XVI]. Page 903-904 (no figure). Schmidt’s Atlas, as Cerataulus pacificus, Schmidt’s Atlas, Plate 155, Fig 10.
All 3 of these are present in Barbados, so that’s no help. This one is 79µm across (through the eyes), 77µm top to bottom. Essentially circular. This would be big for P. ambiguus and P. ambiguus var. major, and perhaps a bit small for R. ralfsianus (although there are smaller circular ones for that mentioned in the ref above). Basically this shows features which could put it into any of these 3 descriptions, but also ones which don’t. If pushed, I’d probably have put this down as Pseudauliscus ralfsianus, but that would have been a very tentative assignment, and it doesn’t match the images for P. ralfsianus in Patricia A. Sims (2001) The Genus Praetriceratium Gen. Nov.: A Survey of Eupodiscoid Genera with a Sipho Marginalis, Diatom Research, 16:2, 399-416, DOI:10.1080/0269249X.2001.9705527. So, a bit of a mystery….
I recently acquired about 60 slides by this maker, so if you want to see others by them, search for AAAAA in the Search option at the top of the page, and I’ll include this in each of the pages for them.