Disclaimer – Normally I don’t do extensive modifications to my images, but this is one where I have.
Entogonia sp. (I think this is E. abercrombieana but more on that later) from Cambridge, Barbados. Single example on the slide, facing upwards. Unknown maker. 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. 36 images stacked in Zerene (Pmax).
There are issues with the mountant/adhesive to the coverslip on this one, including a huge bubble in the middle of the diatom, along with lots of smaller ones across the diatom. Also in the full stack the ‘skirt’ on the underside was quite obvious and distracting. So I removed that to concentrate the focus of the image on the top features, as well as the central bubble (however the smaller features have been left as it was hard to tell what was a bubble and what was surface features on the diatom frustule). I have called this image the ‘cleaned image’ and is the top one above.
There is a good review of this genus in: Holmes, R.W. & Brigger, A.L. (1979). The marine fossil diatom genus Entogonia Greville – A review. Bacillaria 2: 155-214. Looking through this, I think this might be Entogonia abercrombieana (Figs 1-3). I also went back to the original description: Greville, R.K. (1863). Descriptions of new and rare Diatoms. Series X. Quarterly Journal of Microscopical Science, 2nd series. 3: 227-237, pls IX & X. page 235, and (of Triceratium abercrombieana Greville, 1861) Greville, R. K. (1861). Descriptions of new and rare Diatoms. Series IV. Transactions of the Microscopical Society, New Series, London. 9: 79-87. page 83; plate 10, figs. 7-9. It certain does look like the images in figures 7 and 8 in this. My example lacks the really obvious puncta usually associated with Entogonia. I am wondering whether mounting issues are common with this type of diatom. If so, then the smaller bubbles could have been mistaken for puncta in the original images in the desire the see puncta where there aren’t actually any. However that is just speculation. This could also be an aberrant example with no/unusual puncta formation. Whatever it is, it’s quite a striking example of an Entogonia.
I recently acquired about 60 slides by this maker, so if you want to see others by them, search for AAAAA in the Search option at the top of the page, and I’ll include this in each of the pages for them.