Cructose lichen on a seashore. This is Tephromela atra, an example of a crustose lichen, growing on a rocky shore in Western Scotland. This lichen is one of those that contribute to the 'grey zone' (xeric-supralittoral) of rocky shores, the region furthest from the sea that receives spray but is never inundated. This lichen is also widespread inland, where it favours porous and less acidic surfaces. This circular structure if an entire colony, with black apothecial discs developing at centre.