Description: Grey-white crusts that grow on well-illuminated acid rock shout out for attention. P. excludens is one of these. No discs. Thallus pale grey, surface slightly warted, some zoning towards the free edges; soredia in the warts finely granular, white or nicotine-stained yellow, the soralia disc-shaped, concave. Finally, the spot tests: K+ yellow-red; Pd+ yellow. Look out for its twin, the fertile counterpart P. monogona which has its glazed discs sunken into large grey-white warts. Both frequently grow together. On flat, well-lit, siliceous rocks in predominantly unpolluted, coastal areas. Extreme western and northern Ireland.

Key Identification Features:

• Grey-white crust, discs absent but with numerous, concave, dish-like soralia in the warty thallus lined with granular soredia
• Sorediate thallus testing K+ yellow-red.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Lepra excludens at iNaturalist World Species Observations database.