An arrangement of Actinosphenia from Pabellon do Pico (a port in Peru, known amongst other things, for the shipping of guano). Prepared by Arthur Cottam. Olympus BHB microscope using 450nm LED light. 20x Nikon Plan Apo NA 0.65 objective. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 14 images stacked in Zerene (Pmax).
So what is Actinosphenia? These look like Actinoptychus splendens var. halionyx to me and the WoRMS site lists Actinophaenia splendens as an old name for Actinoptychus splendens (shown here). The spelling is close but not the same. However Actinosphenia splendens is mentioned in Studies on Australian and New Zealand Diatoms I.—Planktonic and Allied Species, Transactions and Proceedings of the Royal Society of New Zealand, Volume 85, 1957-58, Page 483 (available here) as being another name for Actinoptychus splendens. So it looks like this are indeed Actinoptychus splendens, and that Actinosphenia and Actinophaenia are old names for them.