Navicula angelorum from Palos Verdes, California. Single example on the slide. No mounters name but that was prepared by JA Long. Mounted in Styrax. At some point the ring around the coverslip was damaged, and someone has repainted it in black. However the immersion oil has solublized and removed that new ring. This has resulted in the outer black ring that is visible on the slide, and revealing the damage to the original one. Olympus BHB microscope using 450nm LED light. 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. 28 images stacked in Zerene (Pmax).