An Aulacodiscus sp.. Single example on the slide and no location given. Prepared by Jame Doke MacPhail. ’07’ so presumably made in 1907. Olympus BHB microscope using 450nm LED light. I tried stacking this with a 20x objective, however the slide is quite low contrast and the resultant image was not good. So this is a single image with a 10x Nikon Plan Apo NA 0.45 objective. Olympus Aplanat Achromat condenser, brightfield lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Single image. The image is of course quite low resolution.
As for what this is the lack of location doesn’t help. So far the nearest I can find is Aulacodiscus brunii from Sendai, Schmidt’s Atlas Plate 169, Figure 11. However I consider this an extremely tentative ID.