A slide of Aulacodiscus orientalis (and something else, more on that in a minute) from the Sandwich Islands (South Atlantic, East of the Falkland Islands). Prepared by Laurence Miles. Olympus BHB microscope using 450nm LED light. Main images with a 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. Image stacked prepared in Zerene (Pmax).
I am assuming the 4 diatoms are the same species, despite the minor visual differences.
Aulacodiscus orientalis. 56 images stacked. Slightly oblique lighting for this one. Processes facing upwards towards the coverslip, with a couple of damaged ones. This diatom was the one on the right hand side of the arrangement image. Published in: Greville, R.K. (1864). Descriptions of new and rare Diatoms. Series XI. Transactions of the Microscopical Society, New Series, London 12: 8-14, pls I, II.
Guitarra Carteri. In addition to the 4 diatoms, there is something else on the slide. I’d seen something like this before, and thanks to Anne Gleich, I was reminded that it is part of a sponge – an ‘Anchorate flesh-spicule of Guitarra‘. I’ve seen these before in slides from Oamaru, New Zealand. It is written about in Hinde, G.J.; Holmes, W.M. (1892). On the sponge-remains in the Lower Tertiary Strata near Oamaru, Otago, New Zealand. Journal of the Linnean Society. Zoology 24(151): 177-262, pls 7-15. page: 213, Plate XI, Figs 1,2,3. 73 images stacked. The lighting on this was a bit more oblique than the Aulacodiscus. The view of this one is looking down through the top surface, with the circular ‘plates’ at either end being on the underside as viewed. These are actually smooth, but show texture as that was picked up from the upper surface during the image stack. In the middle of both plates is a small pinprick feature about 600nm across. Not a diatom, but fascinating anyway, so am including here.