A slide labelled as Triceratium nitescens and obesum from Oamaru, New Zealand. More on these in a minute. Two diatoms, but not really an arrangement, one near the middle and the other near the red ring. No makers name. Olympus BHB microscope using 450nm LED light. 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. Image stacks prepared in Zerene (Pmax).
Ok, the names.
Triceratium nitescens. 30 images stacked. Triceratium nitescens Greville 1865. Published in: Greville, R.K. (1865). Descriptions of new and rare diatoms. Series XIV. Transactions of the Microscopical Society, New Series, London 13: 1-10, 2 pls [I, II]. Page 8, Plate 2, Figure 19. Now known as Trilamina nitescens (Greville) J. Witkowski, P.A. Sims, Strelnikova & D.M. Williams.
The other one, 19 images stacked. Labelled as Triceratium obesum. This name is currently regarded as a synonym of Trilamina obesa (Greville) J.Witkowski, P.A.Sims, N.I.Strelnikova & D.M.Williams. However, I think this is Triceratium denticulatum. T. obesum not reported for Oamaru, T. denticulatum is and looks to be a good visual match. Triceratium denticulatum Greville 1863. Published in: Greville, R.K. (1863). Descriptions of new and rare diatoms. Series X. Quarterly Journal of Microscopical Science, Series 2 3: 227-237, pls IX, X. Page 233, Plate 9, Figure 14. Now known as Trilamina denticulata (Greville) J. Witkowski, P.A. Sims, N.I. Strelnikova & D.M. Williams.
I’ve gone with the new names (Trilamina) for both of these on the labels for them. Good paper on these and others: Jakub Witkowski, Patricia A. Sims, Nina I. Strelnikova & David M. Williams, “Entogoniopsis gen. nov. and Trilamina gen. nov. (Bacillariophyta): a survey of multipolar pseudocellate diatoms with internal costae, including comments on the genus Sheshukovia Gleser”, (Phytotaxa 209), 89 pp.