DESCRIPTION: Foliose.  The thallus can be up to  15cm wide with the dark brown to grey-brown upper surface sporting a somewhat purplish tinge and patterned with a network of pale lines.  The underside is black and gives rise to many simple or rarely branched rhizines. The discs of the apothecia are dark brown with a pale margin. DISTRIBUTION: Found primarily on the west side of Britian with many records from Northern areas too. HABITAT: Can be quite common on nutrient-poor, well-lit, siliceous rocks, with a particular preference for upland areas. This species can be occasionally be found on bark and wood.