Agyriaceae Trapelia coarctata Growth type crustose Chemical results: K-, C+ red, KC+ red, P-, UV+ whitish. Can be abundant on siliceous rocks and stones, bricks and mortar, sometimes found on consolidated clay soils. Very variable. Pink to reddish-brown apothecia, thin white margins often excluded with age, on a thin, +/- smooth, white, bluish-grey or pink-grey thallus. When present prothallus is whitish. Spores simple, 15-25 x 7-13 µm. Microscope photograph below. Sometimes host to Lichenochora coarctatae and Roselliniella microthelia Similar: Trapelia glebulosa and Trapelia placodioides

Microscope photograph

Trapelia coarctata
Brands Bay, Dorset. January 2013