Description: This crustose lichen with a usually thick, warty thallus can form large patches on the dry, sheltered sides of vertical, siliceous, coastal rocks and walls. While the thallus is nothing memorable, the discs (to 1.5mm diam.) are curiously blue-black to black with a wavy edge and an occasional sugaring of pruina which makes it distinctive among other species. Northern and western Ireland.

Key Identification Features:

• Thickish warty thallus on dry, shaded, vertical coastal rocks
• Discs blue-black, lightly glazed with pruina with margin flexuose.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Tylothallia biformigera at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Tylothallia biformigera at iNaturalist World Species Observations database.