Triceratium hardmannianum (spelt hardmanianum on the slide) from College Hill, Barbados. Single example on the slide. Prepared by Arthur Cottam. 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. 72 images stacked in Zerene (Pmax). This was slightly canted in the mountant which led to the high image count for the stack.
Quite a rare diatom, I do have a couple of other examples on this site (here and here). Included below is the information on the diatom I put on the page for the slide by Samuel Henry Meakin;
There seems to historically be two possible spellings for this diatom – T. hardmannianum and T. hardmanianum. It was reported in Greville, R.K. (1865). Descriptions of new and rare diatoms. Series XVI . Transactions of the Microscopical Society, New Series, London 13: 43-57 [last page as “75”], 2 pls [pls V, VI]. It is also known as Crawfordia radiata and Crawfordia hardmanniana and is discussed in; Sims, P.A., Witkowski, J. & César, E.A. (2021). Crawfordia gen. nov.: solving the riddle of Triceratium hardmannianum Grev. (Bacillariophyta). Nova Hedwigia, Beiheft 115: 205-221, 7 pls, 2 tables. The complexity around naming seems to come from it being found attached to frustules of C. radiata so it is perhaps one half of a complete C. radiata and should be referred to as ‘hardmanniana valves’.