Kuettlingeria fuscoatroides (J. Steiner) I.V. Frolov, Vondráket Arup =Caloplaca fuscoatroides J. Steiner

     Thallus crustose relatively thick to quite thin, very irregular, bordered and cracked to subsquamular, very dark, greyish, dark greyish, blackish, prothallus sometimes present, blackish. Apothecia usually quite numerous, sessile, 0.5-1 mm in diameter, flat disc and the remainder, dark ferruginous red, reddish brown a little orange, dark red, very neat and slightly thick margin, not crenate, persistent, lighter and orange. Polarilocular spores, colorless, broadly elliptical, 13-16 x 7-10 µm, with equatorial thickening of 1/3 to 1/2 of the total spore length. Frequent presence of protruding pycnidia with rounded, black apex. Apothecia: K + purple. Not very rare, maritime and thermophilic species occurng to large siliceous stones, dry stone walls, vertical walls of large rocks in the xeric zone of marine shores.

N.B. Easy to confuse with Caloplaca crenularia and especially Caloplaca crenularia var. contigua with a paler thallus and the margin of apothecia crenate and thinner, whose habitat is more extensive and less strictly maritime and also with Caloplaca ceracea very close species (and perhaps conspecific?) but whose habitat is more humid and less acidic and which does not support not so much the sun and the projections of sea water, and whose apothecia disc is a little greenish in wet weather.

N.B. The taxon from the Atlantic coasts is probably different from that described from the Mediterranean coasts.