A couple of strew slides from Wainfleet, Lincolnshire, UK. One labelled “Mixed diatoms” with a wide range of species. The other labelled “Surirella gemma“. Both mounted in Aroclor and dated May 1975. Prepared by Bernard Hartley. Olympus BHB microscope using 450nm LED light. I chose an example of a Metascolioneis tumida from the “Mixed diatoms” slide for high magnification imaging. 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. 29 images stacked in Zerene (Pmax). Some debris visible especially at the lower left of the diatom.
Metascolioneis tumida (Brébisson ex Kützing) Blanco & Wetzel 2016. Published in: Blanco, S. & Wetzel, C.E. (2016). Replacement names for botanical taxa involving algal genera. Phytotaxa 266(3): 195-205. Page 200. Also known as Scolioneis tumida and Navicula tumida. Thanks to Anne Gleich for this ID.
Although these aren’t numbered as such, these two do match the descriptions for slides 667 and 668 from Bernard Hartley’s Sample and Strew Slide Collection PDF (accessed from here).