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(Map updated: 11 August 2009)

Look for this crustose, siliceous rock-inhabiting lichen on rocks by the seashore where it is generally rare. In A. recedens the discs obscure the view of the dark blue-grey thallus, which is warted and cracked with a silky sheen. The discs (to 1mm diam.) are crowded, three-six per areole and black when wetted. Thallus reactions = (K-, Pd-). In Ireland: County Kerry.

Key characteristics

• Thallus blue-grey, obscured by the densely packed discs, black when wet
• On siliceous seashores.

Original text submitted by Vince J. Giavarini