An arrangement of three diatoms labelled as Podosira argus. No makers name, but prepared by Samuel Henry Meakin. Some degradation of the mountant. The largest one in the middle was imaged at higher magnification. It is viewed from the underside with the rim facing the coverslip (as were the other two as well). 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, brightfield lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 63 images stacked in Zerene (Pmax).
EDIT, 17/9/25. Having imaged a lot of slides since this one, and digging a bit deeper, I am now less convinced about this being identified as Podosira argus. In fact I am fairly sure it is not P. argus, but is a Hyalodiscus of some type. While P. argus is domed like this, as far as I can tell it also has an array of circular depressions on the convex side which the ones on this slide show no evidence of.