Dog Lichen (Peltigera canina)
My book says this is a very common lichen found on walls, on rocks, on soil and amongst grass, even on lawns and sand dunes. That may be the case but in five years of looking I have only encountered it twice (so far!) It is a large foliose lichen, that is to say, the main body of the lichen, the thallus, are a bit like leaves.
You may be wondering why this is called dog lichen? Even if you are not I will tell you anyway as I went to a lot of trouble to find out! In amongst the leafy bits are root-like structures that resemble dogs teeth. Because of this it was used as a potential cure for rabies but, of course, it did not work. Early chemists thought that if things looked alike then may be they were connected no matter have far apart they are biologically!
Find out more about dog lichen here: