Lathagrium cristatum (L.) Otalora, M. M. Jorg & Wedin var. cristatum

   Tallus foliose, forming dense tufts rosette-shaped, 2-6 cm diam., deeply lobed, lobes wrinkled, notably concave as minute canals, rather thin, narrow, 2-3 mm wide, radiating up to 1 cm long, margin sometimes highly incised, typically straightened, upper surface olive-green when humid, green-brown to green-black when dry, smooth but sometimes with warted or globular isidia towards the center (if they are very abundant and if the lobes of the margin are very elongated see: Lathagrium cristatum var. marginale, lower surface with dirty whitish hapters. Apothecia more or less abundant, sessile, 2-5 mm diam., disc concave, then flat to slightly convex, red to brown-red, thalline margin thin,  smooth to granular. Elliptical spores with conical ends, submuriform (3-septate possibly subdividing), 18-30 x 8-12 µm according to literature, 20-25 x 8-13 µm according to our measurements. Photobiont : Nostoc. Chemical spot tests negative. Species coming on the limestone rocks well-lit but also on the mortar of the walls. In our prospecting area this species has also been reported on the ground in the calcareous dunes but these observations are doubtful because of the easy confusion with neighboring species.