An arrangement labelled Auliscus and Syndetoneis. No makers name. The slide says “very good slide…. (many?) species”, and then what looks to be “Allans” at the bottom, maybe referring to Allan’s Farm, Oamaru. I’ve been looking at a few slides which look to be from the same unknown maker, and like the others this has issues with the mountant/adhesive which made imaging the diatom a challenge at times. However there are a few unusual ones, and some which I haven’t got on this site so far, so it was worth doing. Olympus BHB microscope using 450nm LED light. I then selected some for imaging at higher magnification with 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. Image stacks prepared in Zerene (Pmax).
Cerataulus johnsonianus. Top row, 1st diatom on the left. Top down view. 61 images stacked.
Hyalodiscus radiatus var. striata. Top row, 2nd from left. Top down view. 39 images stacked. This is an interesting one. There are two distinct nubs/‘processes’, one at 3 o’clock and one at 9 o’clock. Looking back at yesterday’s image from the underside from a different slide (see here), these features are again visible at 10 o’clock and 4 o’clock. These are not obvious in Desikachary & Sreelatha’s images in their book ‘Oamaru diatoms’. I am fairly sure of my ID for this, but like D&S I have questions about this one.
Syndetoneis amplectens. Top row, 3rd from left. Probably S. amplectens var. amplectens based on size and appearance. 50 images stacked. Missing one spike from one end (top right of the image). This name is currently regarded as a synonym of Rutilaria amplectens (Grove & Sturt) R.Ross. Accepted name Hemiaulus amplectens var. amplectens Grove & Sturt, 1887.
Auliscus fenestratus. Bottom row, 3rd from left. 37 images stacked.
Glyphodiscus sp. Bottom row, 4th from left. Maybe Glyphodiscus stellatus or perhaps Glyphodiscus strigillatus (on balance I am leaning more towards G. stellatus). 36 images stacked. Big issues with the dark ring in middle of this one marring its appearance.
Auliscus lacunosus. Bottom row, 7th from left. Underside view with the rim towards the coverslip. 52 images stacked. Some issues with the adhesive being visible in the right hand ocellus.
Auliscus intermedius var. simplex. Bottom row, 8th from left. Underside view with the rim towards the coverslip. 52 images stacked. I am a little more tenuous over this ID, as there are issues with the adhesive obscuring some of the details, but it seems like a good match.
Auliscus macraeanus. Bottom row, 9th from left. Top view. 37 images stacked. I like this one, it reminds me of Archimedes, Nite Owl’s ship in Watchmen.
Overall an interesting slide with some unusual diatoms, but with issues in the mountant and adhesive which present some challenges for imaging.