Diatoms from Sendai, Japan. Some issues with the mountant. Unknown maker. Olympus BHB microscope using 450nm LED light. I three of them for imaging at higher resolution 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. 67 images stacked in Zerene (Pmax).
Rutilaria hexagona var. cornuta Tempère & Brun 1889. Published in: Brun, J. & Tempère, J. (1889). Diatomées fossiles du Japon. Espèces marines et nouvelles des calcaires argileux de Sendaï et de Yedo. Mémoires de la Société de Physique et d’Histoire Naturelle de Genève 30(9): 1-75, pls 1-9. Page 55, Plate I [1], Figure 2. This name is currently regarded as a synonym of Rutilaria obesa Greville ex Cleve. Source of synonymy: Ross, R. (1995). A revision of Rutilaria Greville (Bacillariophyta). Bulletin of the Natural History Museum, London, Botany 25(1): 1-93, 20 pls.
There is also a Cocconeis and an Aulacodiscus in the image.
Cocconeis. I think this could be Cocconeis formosa (Schmidt’s Atlas, Plate 193, Figures 42-47). Cocconeis formosa Brun 1891. Published in: Brun, J.-J. (1891). Diatomées espèces nouvelles marines, fossiles ou pélagiques. Mémoires de la Société de Physique et d’Histoire Naturelle de Genève 31 (part 2, no. 1): 1-47, pls 11-22. Page 16, Plate 18, Figure 6.
Aulacodiscus. Maybe Aulacodiscus beeveriae (2 processes)? Certainly similar. Is it present in Sendai (or a fossil)? However I think Aulacodiscus brownei (Schmidt’s Atlas 36, 15-16) is a good match. Also found in Kettleman Hills Pliocene fossil site (but rare). I think A. brownei (2 process form) is the best fit at the moment. Aulacodiscus brownei Norman ex Pritchard 1861. Published in: Pritchard, A. (1861). A history of infusoria, including the Desmidiaceae and Diatomaceae, British and foreign. Fourth edition enlarged and revised by J. T. Arlidge, M.B., B.A. Lond.; W. Archer, Esq.; J. Ralfs, M.R.C.S.L.; W. C. Williamson, Esq., F.R.S., and the author. pp. [1]-xii, [1]-968, 40 pls [I-XV]. London: Whittaker and Co.. Page 844.
I recently acquired about 30 more slides by this maker to add to the ones I already had, 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.