A slide labelled as Triceratium from Sendai, Japan. Single example on the slide. Prepared by WA Firth. Based on appearance I am fairly sure this is an example of Entogoniopsis stokesiana, which would have originally been known as Triceratium stokesianum.
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. Monochrome converted Nikon d850 camera. 46 images stacked in Zerene (Pmax). There are three ‘blobs’ visible, one at each of the apices, where it is attached to the coverslip.