The bottom image looks a little like a world map of some alien planet rolled out flat, yet this shows Rhizocarpon reductum growing amongst other species of lichen atop an old canal bridge coping stone.
A cructose lichen which is light to dark grey in colour, aereolate forming patches on the substrate. The discs are black with variable flat to pronounced convex surfaces.
Found on silica-rich rocks and old man-made structures. Common and widespread.
Photographs of Rhizocarpon reductum, taken March 2012 on old canal coping stone, Staffordshire. © Pete Hillman 2012. Camera used Panasonic Lumix DMC-FZ38.