Order: Peltigerales       Family: Placynthiaceae Species: Placynthium nigrum Growth type granular or squamulose. 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