Rinodina confragosa (Ach.) Körb.

    Thallus crustose, more or less thick, rimose, flat, presence of understated warts with slightly indented margins, pale grey, whitish cream, prothallus inconspicuous. Apothecia, 0.6-1.5 mm diam., sessile, often crowded together, disc flat becoming convex, black, exciple persitent, erect (up to 0.1 mm tall), concolourous to thallus, little or not crenulate. Ascospores broadly ellipsoid, thick walls, 1-septate with angular locules, 17-27 x 8-13 µm. Photobiont: Trebouxia. Thallus : K+ yellow, Pd+ yellow. Strong maritime trends, on coastal siliceous rocks. Species very similar and sometimes mixed with Lecanora gangaleoides and Tephromela atra which makes its recognition in the field difficult by confusion, but Rinodina confragosa has smaller and more numerous apothecia. N.B. Certain morphotypes with a thallus not greenish or glaucous and with apothecia with little or not crenellated margins and with doubtful P of Rinodina beccariana which is a very close species can only be distinguished by the observation of the spores with rounded locules.