A selection of Stauroneis phoenicenteron (label says Stauroneis acuta ?) from Troy, New Hampshire, USA. No makers name but based on the style this was prepared by Frederick Marshall. Olympus BHB microscope using 450nm LED light. As well as the array I imaged one 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. 24 images stacked in Zerene (Pmax). One on top of another, hence the double rim in places.
This doesn’t look like ‘S. acuta‘ as written on the slide, but it does look like Stauroneis phoenicenteron (Nitzsch) Ehrenberg 1843. Published in: Ehrenberg, C.G. (1843). Verbreitung und Einfluss des mikroskopischen Lebens in Süd- und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1841: [291]–445 + [1, Berichtigungen], pls 1-4. Page 311, Plate 2 Figure 1, Plate 3 Figure 3. S. phoenicenteron is mentioned for Troy here.