Verrucariaceae Verrucaria macrostoma f. macrostoma Growth type crustose Chemical reactions negative. Occurs on calcareous rocks, limestone and on mortar The well-developed, mid-brown thallus is darker in exposed locations but paler brown in shade with rounded or lobed areoles often cracking into large secondary areoles. Areoles are +/- subsquamulose, the black perithecia (3/4 immersed) not leaving pits when decayed. Similar: V. macrostoma f. furfuracea is blastidiate, perithecia absent. V. nigrescens has smaller aureoles, usually darker in colour

Verrucaria macrostoma
Wool churchyard, Dorset. September 2012. Rollright Stones, Oxfordshire, September 2011