An arrangement of Aulacodiscus sp. from Bain’s Upper, Oamaru, New Zealand. Fossil marine material. Sty.Mix (styrax mix) mountant and dated August 1965. Prepared by ECP Bone. Olympus BHB microscope using 450nm LED light. Higher resolution image of the three Aulacodiscus with a 20x Nikon Plan Apo 0.65 objective. Olympus Aplanat Achromat condenser, slightly oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 62 images stacked in Zerene (Pmax).
From left to right.
1. Marker.
2. Aulacodiscus patulus. Aulacodiscus patulus Grunow in A.Schmidt 1888. Published in: Schmidt, A.[W.F.] (1888). Atlas der Diatomaceen-kunde. Series III: Heft 33-34 [“Heft 29-30”]. pp. pls 129-136. Aschersleben: Verlag von Ludwig Siever. Page 134, Figure 6, (5= var.?) Nomen. I was wondering if this was a distorted image as it was in the corner of the frame, but the diatom itself seems to be slightly oval (based on the 10x objective image).
3. Aulacodiscus oamaruensis. Aulacodiscus oamaruensis Grunow in Schmidt 1888. Published in: Schmidt, A.[W.F.] (1888). Atlas der Diatomaceen-kunde. Series III: Heft 31-32 [“Heft 27/28”]. pp. pls 121-128. Aschersleben: Verlag von Ludwig Siever. Plate 124, Figure 9.
4. Aulacodiscus margaritaceous var. debyi[i]. Aulacodiscus margaritaceus var. debyi (Pantocsek) Rattray, 1888. Accepted name: Aulacodiscus debyi Pantocsek, 1886. Original description (of Aulacodiscus debyi Pantocsek, 1886); Pantocsek, J. (1886). Beiträge zur Kenntnis der Fossilen Bacillarien Ungarns. Teil I, Marine Bacillarien. Nagy-Tapolcsány, Buchdrucherei von Julius Platzko, 74 pp., 30 pls. Page 58, Plate 25, Figure 226.
All of these look like reasonable matches.