Lichen with pruinose apothecia

Lichen with pruinose apothecia

Observation - Lichen with pruinose apothecia - UK and Ireland. Description: Whitish, areolate, crustose lichen growing on vertical surface of siliceous rocks on cliff top. Black prothallus. Pruinose, black lecideine apothecia, some convex, almost hemispherical. Chemical tests applied to thallus. C-. K+ slow from yellow to deep r

Whitish, areolate, crustose lichen growing on vertical surface of siliceous rocks on cliff top. Black prothallus. Pruinose, black lecideine apothecia, some convex, almost hemispherical. Chemical tests applied to thallus. C-. K+ slow from yellow to deep red, scarlett. Possibly Porpidia platycarpoides.
Wonder if the small black slits on some of the areoles are simply young apothecia or something else.