Strew slide from Morfa Harlech, North Wales. <600 mesh. Range of species present (obviously smaller ones) and some debris. No makers name but this is by Bernard Hartley. Olympus BHB microscope using 450nm LED light. I chose a couple for imaging at high magnification. 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. Images stacked in Zerene (Pmax).
Gomphonema acuminatum. Fairly sure on this one. 9 images stacked. Gomphonema acuminatum Ehrenberg 1832. Published in: Ehrenberg, C.G. (1832). Über die Entwickelung und Lebensdauer der Infusionsthiere; nebst ferneren Beiträgen zu einer Vergleichung ihrer organischen Systeme. Abhandlungen der Königlichen Akademie Wissenschaften zu Berlin, Physikalische Klasse 1831: 1-154, pls I-IV. Page 88.
63xL ob, 11 images Pmax. I think this is Frustulia torfacea (based on a visual ID from the Diatoms Flora of Britain and Ireland here). Frustulia torfacea A.Braun ex Rabenhorst 1853 (as ‘F. torfacea A. Braun in litt. c. ic.’). Published in: Rabenhorst, L. (1853). Die Süsswasser-Diatomaceen (Bacillarien.): für Freunde der Mikroskopie. pp. [1]-xii, [1]-72, 10 plates [I–X]. Leipzig: Eduard Kummer. Page 50, Plate 7, Figure 2. I am however not 100% on this so have left it with a question mark for now. Looks almost like a small version of Frickea lewisiana to me.
There is an entry from Bernard Hartley’s Sample and Strew Slide Collection PDF for this – slide 538 – accessed from here, where it says the following; “538 – Chocolate brown coloured algae floating on lowland (?brackish) stream parallel to bottom road from Harlech to Ynys, Merioneth, Wales [collected] 14th May 1974.”.