Auliscus racemosus from Guañape guano. single example present. Described as ‘extremely rare’. Prepared by AC Cole. Some damage to the corners of the slide. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.40 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, brightfield lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 55 images stacked in Zerene (Pmax). This was a challenge to stack, especially preserving the look of the puncta. This can be seen when you look at part of one of the single frames from the image stack. Also the diatom was not flat, but tilted slightly. This increased the number of frames needed, but also given the final image a good 3D look with shadowing even though it was a simple brightfield image.
As I was preparing this to upload to the site, I realized that I’ve actually got another example of A. racemosus already on the site on a slide by WA Firth – here. This does look similar although there are some differences especially around the middle. Also I processed/stacked the image in this page image slightly differently, so the puncta look a lot cleaner here as I spent much more time cleaning this image up. With it being described as ‘extremely rare’ on this slide, I looked for some details on it, and found the reference – Greville, R.K. (1863). A monograph of the genus Auliscus. Transactions of the Microscopical Society, New Series, London, 11(3): 36-53, pls II & III page(s): p. 46; pl. 2, fig. 9. I have included relevant screenshots from that reference.