Crustose Lichen on tombstone.

Crustose Lichen on tombstone.

Observation - Crustose Lichen on tombstone.. Description: Crustose lichen on large tombstone on very exposed hillside.Large patch covering much of the tombstone. Thallus pale grey,thick and warted in central area,with white edging (prothallus). This may be O.tartarea; help with this please?

Crustose lichen on large tombstone on very exposed hillside.Large patch covering much of the tombstone. Thallus pale grey,thick and warted in central area,with white edging (prothallus).

This may be O.tartarea; help with this please?