Slide labelled as Triceratium arcticum var. (?) from Sendai, Japan. Single example on the slide. This name is currently regarded as a synonym of Trigonium arcticum (Brightwell) Cleve, so this is likelyTrigonium arcticum var. quadrata. Prepared by WA Firth. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, brightfield lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 30 images stacked in Zerene (Pmax).
EDIT 04/12/25 – having looked at a few more images, this could potentially be an example of Triceratium arcticum var. californica as it also looks similar to that. However I am not 100% convinced, so leave it as a possible name for now.