Two examples of a Surirella sp. from the Philippine Islands. More on the name in a minute. Cracked coverslip. No makers name, but based on style I think this is by JA Long. 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. 40 images stacked in Zerene (Pmax). The one on the right is an underside view, with the rim to the coverslip.
Back to the name. The slide says ‘near triumphans’ in pencil. There is a Surirella triumphans. Surirella triumphans Schmidt in Schmidt et al., 1897. Original description: Schmidt, A. (1897). Atlas der Diatomaceen-kunde. Leipzig. O.R. Reisland, Series V(Heft 52-53): pls. 205-212. Plate 206, Figure 20. However I do not think this is S. triumphans based on Schmidt’s Atlas image.
It does however look like Surirella mollis, which is in Schmidt’s Atlas Plate 206, Figure 19, which is next to S. triumphans on the plate… Surirella mollis A.W.F.Schmidt 1897. Published in: Schmidt, A.[W.F.] (1897). Atlas der Diatomaceen-kunde. Series V: Heft 52/53. pp. pls 205-212. Leipzig: O.R. Reisland. Plate 206, Figures 18,19. This came from Sumbawa, south of the Philippines according to Schmidt, so could be correct. But not sure, need other images to confirm.
Another possibility – Surirella laxa Janisch, Schmidt’s Atlas Plate 56, Figures 3-5. Basically, I’m currently not sure as to species. Any ideas, please let me know.