Haloplaca sorediella (Arup) Arup, Fröden & Søchting = Caloplaca sorediella Arup

   Thallus often in tiny patches, 5-10 (15) mm diam., of tiny, contiguous or scattered, bullate areoles producing a verruculose aspect, pale yellow, slightly bright greyish yellow-orange when moist, most often dull whitish, pale greyish, pale grey-greenish  when dry or in shaded places, covered with punctiform soralia developing from bullate areoles, markedly convex, rounded, becoming crowded, with powdery aspect, turning bright orange, bright yellow-orange, and breaking into bright golden-yellow farinose soredia. Apothecia rare, and most often absent, to 0.3(-1) mm diam., orbicular, concave at first but becoming flat, disc orange, thalline margin present when young, yellow, becoming sorediate. Ascospores: ?. Photobiont: trebouxioide. Thallus: C-, K-, KC-, Pd-, soredia and apothecia C-, K+ red, KC+ red, Pd-, UV+ bright orange. ln coastal situations on dead stems of Crithmum maritimum, Armeria maritima and Spergularia maritimea, more rarely on other lichens (Verrucaria) or on tree trunks; also on all kinds of rocks together with other lichen species including  Caloplaca britannica, Caloplaca microthallina and sometimes Caloplaca marina and Verrucaria (Hydropunctaria) maura. Recently described species (2006), apparently endemic of the Scilly Islands, South Ireland, Cornwall and Wales.  Also recently found in the Finistère at the Head of Brittany and Brittany Islands. Characterized by its development on decaying coastal plants, and also on rocks, grey-whitish at first, slightly orange and later farinose golden-yellow.

_ Very close to Solitaria (Caloplaca) chrysophthalma) which grows on the bark at the base of the trunks but whose thallus is immersed in the substrate and barely visible, flattened soredia and which generally has bright orange apothecia.

_ Not to be confused with Caloplaca citrina agg. that sometimes can extend to the supralittoral zone.