Trinacria muelleri Pantocsek from a South Atlantic Eocene Core (spelt muellerii on the slide). Single example on the slide. I think it is an underside view, and it is tilted with the bottom right being closer to the coverslip. Mounted in Naphrax and dated December 1974. Prepared by ECP Bone. 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. 11mm removed from the tube to the camera to increase the field of view. Monochrome converted Nikon d850 camera. 61 images stacked in Zerene (Pmax).
Oddly enough I have not been able to find where this was originally described. If I do so I will add it here.