Slide labelled as Bellerochea malleaus from the North Sea, arranged between two disc diatoms (although some examples have moved). Yellowing of the mountant. No makers name. Olympus BHB microscope using 450nm LED light. As well as the arrangement I selected one for imaging using 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. 40 images stacked in Zerene (Pmax).
Bellerochea malleus (Brightwell) Van Heurck, 1885. Published in: Van Heurck, H. (1885). Synopsis des Diatomées de Belgique. Texte. pp. [1]-235. Anvers: Martin Brouwers & Co. Page 203. Basionym: Triceratium malleus Brightwell. However I will say these look like Lithodesmium undulatum Ehrenberg to me, so am leaving it with a question mark for now.
I have recently imaged a few slides by this maker, all of which are nice. If you want to see others search for CCCCC in the ‘Search’ function.