Lecidea

Lecidea is a genus of crustoselichens with a carbon-black ring or outer margin (exciple) around the fruiting body disc (apothecium), usually (or always) found growing on (saxicolous) or in (endolithic) rock. Lichens that have such a black exciple are called lecideine, meaning "like Lecidea, even if they are not in this genus. Members of the genus are commonly calleddisk lichens or tile lichens.