Belonia nidarosiensis (Kindt) P. M. Jorg et Vezda

    Thallus crustose relatively thin and superficial, whitish a little pinkish, pale greyish, creamy, covered with powdery pink-orange, "carrot", orange-red granules, becoming creamy in the herbarium. Apothecia very rare, rounded, pale pink, pale orange-pink, visible, as a more or less open pore, at the top of warts scattered on the thallus, 0.2-0.4 mm in diameter. Spores of variable size, long elliptical with pointed tips, 12-15 times laterally septate, 40-60 x 10-15 µm. Negative colored chemical reactions. Photobiont: Trentepohlia Cf. umbrinum which gives its color to the thallus and which is clearly visible in yellow-orange when scratched or in eroded places (and also in yellowish in places rubbed when the usual reagents are applied). Species not especially maritime rather rare sensu-stricto on the vertical faces of limestone rocks protected from direct rain but also on old dry walls with little acidity (or become alkaline by their lime mortar) in particular chapels, cement and also concrete blockhouses on the seashore. NB Often in the company of Opegrapha gyrocarpa some sterile forms with little orange or without lemon yellow colorings will be separated by their red C + reaction, just like certain very pink forms of Llimonaea sorediata with the black hypothalle and with a bright red C + reaction. Poorly developed Trentepohlia species, even colonies of single algae such as Trentepohlia aurea, are sometimes difficult to separate but the latter species has a cottony appearance and a bright orange color. Also watch out for Porina linearis with black perithecia.

NB We have adopted here a strict interpretation of this species because under this name it has sometimes been described in reality free and lush forms of Trentepohlia Cf. umbrina which in our prospection area are very frequent and often form large colonies visible from afar on damp walls and in the shade of chapels.