Species: Placynthium nigrum
Photos: On limestone rocks. The Burren, W Ireland.
BLS Burren meeting 2009
Black or sometimes brownish thallus of very small squamules with wide, felted, dark bluish-black prothallus. Apothecia with small, glossy, black discs. Thallus very occasionally grey-pruinose.
Widespread in Ireland on slow-drying calcareous rocks, old mortar and the tops of flat tombstones. Chemical reactions negative.
Similar: P. subradiatum. Rare, mainly in the Burren, Co. Clare
Placynthium nigrum. BLS Burren meeting, April 2009