Aulacodiscus huttonii (4 processes) from Oamaru, New Zealand. Single example on the slide, with a very yellowed mountant (exposure times when imaging with 450nm light were about 10 times that of normal). No makers name but I am fairly sure this is by Sydney Chaffers. On the back of the slide it says, Schmidt’s Atlas Plate 124, Figure 6 and Plate 146, Figure 8. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, slightly oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 42 images stacked in Zerene (Pmax). In the initial full stacked the processes got a bit lost with the other detail around them, so I ended up stacking these separately and then copying them into the full stack in Zerene during the image clean up.
Aulacodiscus huttonii Grove & Sturt 1887. Published in: Grove, E. & Sturt, G. (1887). On a fossil marine diatomaceous deposit from Oamaru, Otago, New Zealand. Appendix. Journal of the Quekett Microscopical Club, Series 2 3(19): 131-148, pls 10-14. Page 140, Plate XII [12], Figure 31.