Strew slide from Allan’s Farm, Oamaru, New Zealand. Mounted in Styraclor and dated October 1995. Wide range of species present, including Stephanopyxis sp., Kittonia elaborata, Stictodiscus sp., Aulacodiscus sp., Asterolampra decora and Brightwellia sp.. Olympus BHB microscope using 450nm LED light. 10x Nikon Plan Apo NA 0.45 objective and brightfield light for the lower magnification strew images. I also selected two which were close together for higher magnification imaging using 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. 35 images stacked in Zerene (Pmax) and 10 images for spikes on ‘Coscinodiscus’.
For the one on the left. ‘Spikes’ in rim upwards towards the coverslip. Thalassiosira excentrica ? Coscinodiscus angulatus (are these the same?)? Coscinodiscus angulatus (D&S, Plate 112, Figures 5,6), Thalassiosira excentrica (D&S, Plate 112, Figures 3-5). Plate 112, Figure 5 is perhaps both C. angulatus and T. excentrica?? D&S mention ‘showing an octagonal figure at inner edge of border’ and ‘apiculi obvious, placed at the angles of the octagon’ for C. angulatus. ‘Apiculi numerous, distinct, inserted within the border at subequal distance apart’ also for T. excentrica. Thalassiosira eccentrica (Ehrenberg) Cleve 1904. Published in: Cleve, P.T. (1904 ‘1903’). Plankton table for the North Sea. Conseil Permanent International pour l’Exploration de la Mér 1903-1904: 216 only. Page 216 (as ‘excentrica‘). Basionym: Coscinodiscus eccentricus Ehrenberg. Coscinodiscus angulatus Greville 1864. Published in: Greville, R.K. (1864). Descriptions of new and rare Diatoms. Series XI. Transactions of the Microscopical Society, New Series, London 12: 8-14, pls I, II. Page 9, Plate II, Figure 11. I’m leaning towards C. angulatus for this, but also consider than C. angulatus and T. eccentrica maybe describing the same thing.
The one on the right. An underside view. Melosira saturnalis ? Melosira saturnalis Brun 1892. Published in: Schmidt, A.[W.F.] (1892). Atlas der Diatomaceen-kunde. Series IV: Heft 45/46. pp. pls 177-180. Leipzig: O.R. Reisland. Plate 180, Figure 24. Fairly sure about this, but am leaving it with the question mark for now.