An arrangement of Aulacodiscus diatoms from Sendai (written as Sandai on the slide), Japan. Mounted in Styrax. Some yellowing of the mountant. Lower label has ‘Aulacodiscus voluta-coeli‘, and ‘A. tumulifer ?’ written on it with amoneus crossed out. No makers name. Olympus BHB microscope using 450nm LED light. As well as the arrangement, I imaged the lower left one using the 40x Leitz Pl Apo NA 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 76 images stacked in Zerene (Pmax).
So, what are these. Aulacodiscus voluta-coeli Brun 1892. Published in: Schmidt, A.[W.F.] (1892). Atlas der Diatomaceen-kunde. Series IV: Heft 43/44. pp. pls 169-176. Leipzig: O.R. Reisland. Plate 170, Figures 5,6 (as ‘Voluta Coeli‘). Reported for Sendai. The two at the bottom of the arrangement certainly look like the drawing in Schmidt’s Atlas, so that name could well be right. The top one is more damaged, but the more I look at it, the more I think it is also the same species (although I am less sure about that one).
Would need better comparison images for Aulacodiscus voluta-coeli to be certain about this identification though. The main image does look quite like Aulacodiscus pretiosus in: Mann, A. (1925). Marine diatoms of the Philippine Islands. Bulletin United States National Museum 100(6, part 1): 1-182, 39 pls. Page 31, Plate 6, Figure 2. This is described as a new species and that it does look like A. voluta-coeli. The photograph in Plate 6 does look quite like these ones. I’ll leave it with a question mark for now.
I’m not sure on the maker for this, but I have just imaged a few of them by the same maker, and they are all interesting slides. If you want to see others by this maker search for BBBBB in the search function.
EDIT – based on the handwriting and style, and some conversations with experts, I this could be by Edmund Grove (of Grove and Sturt). But I have no 100% proof of this at the moment.