Description: Thallus foliose, homoiomerous, gelatinous when wet, often forming 2-3(-4) cm wide, irregular rosettes, deeply and broadly lobed. Lobes often crowded and imbricate, 0.5-1(-5) mm wide, 65-130(-200) µm thick when moist, rounded, flat or concave, often ascending and ear-shaped, olive-green or greenish black (more green in shaded situations), with at first globular, then flattened isidia. Lower surface usually paler than upper surface, with white hapters. Upper and lower cortices absent, but medulla partially paraplectenchymatous. Apothecia rather rare, with a slightly constricted base, up to 1 mm wide, with a brown disc and a thin, finally often excluded, granulose to lobulate thalline margin. Amphithecium without a pseudocortex; proper exciple thin, subparaplectenchymatous; hymenium colourless, 105-110 µm high; paraphyses c. 2 µm thick at mid-level, the apical cells up to 5 µm wide; hypothecium colourless. Asci (6-)8-spored, narrowly clavate, the apex thick, with a I+ blue apical dome and a I+ blue annulus projecting downwardly. Ascospores submuriform, hyaline, broadly oblong to ellipsoid, with rounded or acute ends, 15-20 x 7-8.5 µm. Pycnidia immersed, pale. Conidia bacilliform, usually slightly swollen at the ends, 4.3-5 x 1.2-1.5 µm Photobiont cyanobacterial (Nostoc), in short chains with less than 4 cells. Spot tests: all negative. Chemistry: without lichen substances.
Note: this species, related to B. crispa, was described from Asia. All European records derive from Degelius (1986), and - in my opinion - they could prove to refer to B. crispa.