A nice arrangement of what looks to be 12 Polymyxus sp. (P. coronalis ?) around a central Coscinodiscus diatom. Label says ‘Warri, Nigeria’ presumably referring to the Warri River. The original label – ‘Triceratium, Oamaru‘ – has been crossed out. One has moved and is now visible on its side, which was actually really helpful in identifying them as Polymyxus. I am leaving this as ‘unknown maker’ at the moment, however I have slides of a very similar style by the Manchester Microscopical Society, and Sydney Chaffers. Olympus BHB microscope using 450nm LED light. I did a higher magnification image of the one at 8 o’clock in the arrangement. 63x Leitz Pl Apo NA 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 72 images stacked in Zerene (Pmax).
Some more information about Polymyxus in: J. Nelson Navarro & Rosa G. De Peribonio (1993) A light and scanning electron microscope study of the centric diatom Polymyxus coronalis (Bacillariophyta), European Journal of Phycology, 28:3, 167-172, DOI: 10.1080/09670269300650261. I did a quick search it it does seem that P. coronalis has been reported in Nigeria. Based on the arrangement above though there looks to be quite a variation in appearance for them.