This was growing on a old stone wall on the coast
Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
No interactions present.
There are two very similar ones common on acidic coastal rocks, Tephromela atra and Lecanora gangaleoides ......
They both test K+ yellow but if you cut the apothecia (discs) in half T. atra is purplish-red in section and Lecanora gangaleoides dark green-brown.
Slightly easier in the field is to pick at the thallus with a finger-nail. In the case of Lecanora gangaleoides, yellow-orange pigment (anthraquinone) is exposed in the deeper levels of the medulla (flesh). The pigment tests K+ purple.
The photograph appears to be typical Tephromela atra.
Lat/Lng: 58.2, -5.4
OS grid ref: NC0333