What is "lecidea"

Lecidea is a genus of curstose lichens 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 called disk lichens or tile lichens.