Aspicilia

Aspicilia (sunken disk lichen) is a genus of mostly crustose areolate lichens that grow on rock. Most members have black apothecia discs that are slightly immersed in the areolas, hence the common name"Given the same reason, the naming of Aspicilia is derived from the Greek word for "shield concave". Most of the species of this genus grow on calcareous and acidic rocks and most of the taxa prefer temperate and arctic habitats. Some members of the genus Aspicilia are pioneer species on granite and other hard rock, after which members of other lichen species may grow on them, such as members of Acarospora. ...read more on Wikipedia.