Reichlingia dendritica (Leight.) Ertz et Sanderson = Arthonia atlantica P. James

    Thallus crustose, isolated but often in mosaic with others, quite thin and less than 0.5 mm thick, cracked, areolate and often arachnoid in places, densely covered with minute whitish crystals, white, whitish to pale grey, sometimes greenish  towards the margin, blackish arachnoid hypothallus (the thallus can sometimes have orange tones due to the presence of a Trentepohlia). Apothecia very small, 1-1.2 x 0.10-0.15 mm, blackish but often grayish because they are powdered with whitish, buried and barely visible at least at the beginning, roughly elliptical, irregular, elongated or star-shaped, can form a reticulum and then giving the appearance of an Enterographa. Spores becoming brown when mature, 3-4 septate, oblong to subcylindrical with one end enlarged, 16-24 x 6-7 µm. Thallus: C-, K+ yellow, KC-, P- or P+ yellow or red, UV-. Photobiont: Trentepohlia. Coastal species of oceanic forests with Ilex typically found under the overhangs of large siliceous rocks, or on their faces in the shade, sometimes on walls, often in the company of Enterographa zonata and Gyrographa gyrocarpa.

Two varieties have been described:

var. atlantica with confluentic acid and atranorin.

var. positiva P. James to stictic acid.

N.B. May sometimes present a similar appearance to certain taxa of Roccellographa circumscripta with a thicker thallus, K- but KC+ pale yellow and P+ bright yellow, golden yellow and with spores, 4-7 septate. In fact, in the field considering macroscopic and chemical spot tests results, all the intermediate specimen between these 2 taxa may be found and studies would be necessary to clarify things.

N.B. The chemical tests and the resulting colours are sometimes difficult to analyse due to the orange photobiont and to the fact that this species (as most of its neighbours) seems to be a parasite.