Sticta atlantica  

Thallus initially developing as tongue-shaped or palmate lobes from a short central stipe, becoming suborbicular or irregular, 4–7 cm diam., sometimes forming large colonies that can reach ca 15 cm across, subcoriaceous when wet and usually papery and brittle when dry. Lobes with 1–2 levels of branching, rarely irregular, 10-18 mm broad, adnate to slightly ascending, imbricate and overlapping, plane or undulating, the apices rounded, plane to slightly revolute, crenate to lacerate, the margin not thickened. Upper surface costate, irregular, with regular or irregular swellings or grooves, brownish or bluish grey, the same colour when wet or dry. Cilia absent (rarely found on regenerating lobules). Isidia always present, marginal or laminal; when marginal forming a marginal string of coralloid or subsquamiform minute structures, sometimes becoming distinctly stipitate; when laminal, always starting their development on the swellings or ridges, and forming stipitate coralloid to corymbose masses to 1 mm diam., coarse or delicate, usually shining, concolorous with the thallus. Lower surface foveolate to scrobiculate, white, cream-colored to brownish, tomentum sparse towards the margin but sometimes becoming very dense towards the centre. Cyphellae always present, abundant, round to slightly irregular, rather angular on old lobes, cupuliform to urceolate with a wide pore, prominent, with an erect, white or cream-colored margin, the surface cells not papillate. Photobiont Nostoc.
Anamorph and teleomorph: not known.