Verrucaria muralis

Crustose, cracked-aerolate or endolithic, saxicolous, usually lapidicolous, on calcareous rocks.
Note: perithecia usually semi-inmersed in the thallus:

Ostiole inconspicuous to excavate:

Spores narrowly to broadly ellipsoidal, 17-25 x 10-14 micras:

Thallus cracked-aerolate, grey-green or grey-brown:
Lithology: limestone
Altitude: 860 m
Municipality: Felix