Also called ‘Black Tar Lichen’, it is often confused with oil because of its sooty black nature. It has a regular, almost rectangular areolate pattern. The reproductive bodies are tiny black spots.
It occurs on many types of seashore rock, and is often found above the barnacle zone. It can tolerate sea spray and periodic immersion. Widespread and common on rocky shores around the British Isles.
Photograph of Tar Lichen (Verrucaria maura), taken April 2013, on boulder, Llandudno, Wales. © Pete Hillman 2013. Camera used Nikon Coolpix P500.