Order: Pertusariales       Family: Megasporaceae Species: Circinaria calcarea (Aspicilia calcarea) Growth type crustose. Photos: On gravestones and limestone pavement. Ireland. The thallus is smooth, white to pale-grey, usually areolate and often surrounded by a zoned, cracked, grey prothallus. Black discs with distinct margin that usually does not persist as the apothecia mature. The asci are 4-8 spored, spores simple, 18-30 x 14-27 µm. Chemical reactions negative. Common on limestone walls and tombstones but is not found on cement or mortar. Can form large patches to 40cm. diameter. Similar: Aspicilia contorta (K-,C-) and A. cinerea agg (K+ red)

Aspicilia calcarea. On gravestones and limestone pavement.