in Sagra, Hist. Phys. Cuba, Bot. Pl. Cell. 2: 188 (1842) [1838-1842].
Basionym: Lecidea sorediata Ach., Syn. Meth. Lich. (Lund): 54 (1814).
Protolog type data: America septentrionale [sic!].
Type locality: North America, Mühlenberg s.n. (UPS - isotype).
Thallus: foliose, + orbicular, loosely adpressed, grey to brownish grey, somewhat darker towards the margins. Lobes rounded, concave and slightly erose at the ends with marginal, white pseudocyphellae distinctly contrasting with the dark lobe margins. Pruina mostly on the outer parts of the lobes, typically spotted. Soralia margina, distinctly delimited but spreading onto the lamina and forming round patches. Soredia granular and dark grey, giving central parts of the thallus a dark grey colour. Underside black to greyish black with simple, black rhizinae. Upper cortex paraplectenchymatous, lower cortex prosoplectenchymatous. Medull yellow to orange-yellow. Apothecia and pycnidia not seen in European material (Moberg 1983: 162).
Photobiont: Data lacking.
Chemistry: UV-; all spot tests negative. In the microscope the lower cortex and the rhizinae become weakly violet in K. In t.l.c. a characteristic pattern of unidentified triterpense is formed (Moberg 1983: 162).
Ecology: Mainly on mossy rocks.
Distribution type: Data lacking.
Taxonomy: When Degelius (1941) treated the Azorean material he considered that from Europe to be very close to that from North America but differing in the colour of the medulla and habitat. However, such differences have not been substantiated by later workers (Imshaug 1957: 259; Swinscow & Krog 1975) or by my own investigations (Moberg 1983: 163).
Note: