‘Odontodiscus’ varieties from Maryland, USA. Fossil material. Prepared by Arthur Charles Cole. Olympus BHB microscope using 450nm LED light. 20x Nikon Plan Apo 0.65 objective. Olympus Aplanat Achromat condenser, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 21 images stacked in Zerene (Pmax).
These look to be a mix of Coscinodiscus and Actinocyclus diatoms, and I understand Odontodiscus is an old name which covered a wide range of these disc diatoms.