A slide with 4 Aulacodiscus sp. from Oamaru, New Zealand. Slide says ‘elegans 8 (8 processes), Rattrayi 32 (two, each with 3 processes), and ‘?’ 8 (an unknown one with 8 processes). Prepared by Arthur Cottam. Olympus BHB microscope using 450nm LED light. As well as the arrangement, I imaged two using the 63x Leitz Pl Apo NA 1.40 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Images stacked in Zerene (Pmax). In the 20x image, the two on the left are Aulacodiscus rattrayi, the upper right one I am not certain about, and the lower right one Aulacodiscus elegans.
Upper right. 59 images stacked. Possibilities, Aulacodiscus angulatus var. plana (very tentative ID). Aulacodiscus tabernaculum – overall appearance looks pretty similar (for instance see) but more processes than would be expected. Not sure….
Lower right. 52 images stacked. Aulacodiscus elegans 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, Figure 30.