Slide labelled as ‘Pleurosigma strigosum‘, mounted in mono-bromonaphthalene’. However I suspect these are a Gyrosigma sp. rather than Pleurosigma sp. Mountant, mono-bromonaphthalene looks to have degraded/dried out, which is not uncommon for examples of this. It was surprisingly low contrast in the high resolution images. Prepared by Laurence Miles. Olympus BHB microscope using 450nm LED light. As well as the strew I imaged two diatoms with the 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).
They majority of the diatoms on the slide look like a Gyrosigma sp. to me. Maybe G. acuminatum or G. attenuatum? The Cocconeis may be Cocconeis scutellum.