A strew slide of Bermuda earth (with Heliopelta). More on the name in a minute. No makers name. Olympus BHB microscope using 450nm LED light. I selected what I think it an example of Mastogonia crux to image 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. 45 images stacked in Zerene (Pmax). Viewed directly from above, with the rim down away from the coverslip. Some debris across the surface.
Mastogonia crux Ehrenberg 1844. Published in: Ehrenberg, C.G. (1844). Untersuchungen über die kleinsten lebensformen im quellenlande des Euphrats und Araxes, so wie über eine an neuen formen sehr reiche marine tripelbildung von den Bermuda-Inseln. Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich-Preussischen Akademie der Wissenschaften zu Berlin 1844: 253-275, 1 pl. Page 269.
Bermuda earth is not from Bermuda, but near to Nottingham, Maryland. For example see here – https://groups.io/g/diatom-forum/topic/nottingham_dunkirk/45663579
The ‘Heliopelta’ on the slide label is presumably as there are a few examples of Actinoptychus heliopelta on it.