Family: Verrucariaceae
Verrucaria mucosa Wahlenberg
Type: Crustose
A thin, encrusting lichen, mid to dark green, found on rocks of the lower intertidal zone. Often with a white prothallus, it has a smooth, oily appearance. The perithecia are black, largely embedded in the thallus but more obvious when dry
References:
Smith, C.W. et al. editors (2009) The Lichens of Great Britain and Ireland
Dobson, F.S. (2018) Lichens: an Illustrated Guide to the British and Irish Species