Circinaria contorta (Hoffm.) A. Nordin, S. Savić & Tibell

Mycologia 102, 6: 1341 (2010).

Basionym: Verrucaria contorta Hoffm., Descr. Adumb. Plant. Lich. 1(4): 97 (1790).

Thallus: 5 - 8 - 10 cm in diameter or more, rather thick, forming more or less circular patches, reduced to scattered, rarely crowded, more or less crowded areoles, 0.2 - 1.2 - 1.8 mm in diameter, often convex, grey to chalky-white; prothallus indistinct, never deliminating. Apothecia 0.2 - 0.6 - 0.8 mm diameter, mostly 1, more rarely up to 3 per areole. (Purvis et al. 1992)

Ecology: On calcareous rocks and hard limestones, more often than calcarea on mortar, concrete and impure limestones. Common. (Purvis et al. 1992)

Molecular data:

Distribution: Widespread in Europe and North America.