Picture taken on the 5th April 2008 at Sant Vicens de Castellet, Barcelona, Cataloniaon a flat surface, brick.
Very common in Catalonia, on constructive material, resistent to pollution.
Crustose lichen, thallus from green-brown to dark brown, areolate, surrounded by a thin prothallus. Perithecia black, more than one half immersed, less than 1 mm in diameter (if more than 1 mm probably V, macrostoma, see it in this virtual guide).
It is difficult to separate from Verrucaria nigrescens, but V. nigrescens normally grows on calcareous rocks.