Bit of a frustrating slide this one. Labelled as ‘Stictodiscus buryanus‘ from Santa Monica, California, USA. Named J. Lizars, Optician, Glasgow. Ok, why the frustration? There are three diatoms on here, one Arachnoidiscus sp. and two Stictodiscus sp., neither of which I think are S. buryanus. As I am not convinced by the name of the diatom, can I trust the location? The name tag is J. Lizars. This is not the slide maker, but the slide seller. I have another slide with this hand writing, but I am yet to be 100% on the maker.
Olympus BHB microscope using 450nm LED light. As well as the arrangement, I imaged each one individually. The Left and Middle ones were imaged using a 63x Leitz Pl Apo NA 1.4 oil immersion objective, the Right one with a 40x Leitz Pl Apo NA 1.00 oil immersion objective. 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).
As for what these are, I am not certain. The Arachnoidiscus sp. I am not sure of the species. Strangely enough the two Stictodiscus might be S. hardmanianus. This came from looking through Schmidt’s Atlas. The one on the right looks like Stictodiscus hardmanianus (Schmidt’s Atlas, Plate 452, Figure 1). Translation. “San Pedro, California. Fossil marine. See also Plate 445, Figure 6. Also Stictodiscus hardmanianus Grev.. The central pore ring is missing and, according to the illustrations of this species available so far, was not likely to be of systematic importance.”. This is a reasonable looking match.
The middle one could also be S. hardmanianus (but with the ‘central pore ring’ visible) Schmidt’s Atlas Plate 445, Figure 6. Also perhaps S. californicus (Schmidt’s Atlas, Plate 444, Figure 4).
However these S. hardmanianus don’t look particularly like the ones from Oamaru, so everything is with a question mark for now.