Auliscus species from Rio [de] Janeiro. Single example on the slide. Prepared by Laurence Miles. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo NA 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 51 images stacked in Zerene (Pmax). Couldn’t get close enough to use the 63x Leitz objective unfortunately.
As for species, I think this is likely to be Auliscus grunovii. Auliscus grunovii A.W.F.Schmidt 1875. Published in: Schmidt, A.[W.F.] (1875). Atlas der Diatomaceen-kunde. Series I: Heft 8. pp. pls 29-32. Aschersleben: Verlag von Ernst Schlegel. Plate 30, Figure 14 (as ‘Grunovii‘). Reported in there for ‘Rio’. Also seen spelt as grunowii. A good visual match so I am pretty confident about that ID.