The pale grey thallus is thick and areolate with a blackish prothallus. Apothecia (1-2.5mm) are black, both round and irregular, often immersed into the thallus with flat discs and margins that are often swollen.

On hard, exposed rocks (both siliceous and slightly basic), often dominant on coastal rocks but also common inland.

All year round

Widespread and fairly common.

Fairly frequent in Leicestershire and Rutland.