Slide labelled as “Plate valve of Actinocyclus sp.?” from Nagy Curtos, Hungary. Single example on the slide. Prepared by Henry Jame Baker. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 15 images stacked in Zerene (Pmax).
Back to the name. I am fairly confident this is an Actinocyclus (see the hole at the 12 o’clock position), but it does have its rim missing. Having looked at various examples, it could be Actinocyclus octonarius var. octonarius. Note the image is relatively low resolution. I couldn’t get close enough with the 63x objective I would have preferred to use, so 40x it was. Also, the coverslip ring had been repaired at some point with black paint – some of it came off with the immersion oil. This is a pet peeve of mine. Grrrr…..