Picture taken on the 20th April 2008 at Targasonne, Oriental Pyrenees, France, on a wall, siliceous rock, very common.
Crustose lichen, grey with a tinge of blue in the var. grisella, thallus cracked into areoles, up to 3 mm wide, limited by a black prothallus. Apothecia a little bit immersed, large, 2 mm diam., disc black, often white-pruinose.
Thqallus K+ , yellow and Cl+ red
See C. Perez et alter (2003) Guía dos liques de Galicia, pag.224.