Diplotomma alboatrum (Hoffm.) Flot.
Lichen alboater Hoffm., Enum. lich. eur.: 30 (1784).
Thallus rosette-forming in rounded patches 1-4(-10) cm, often coalescing and covering very large areas, white to grey-white, effuse or subfarinose or forming a rather thick areolate-cracked crust, occasionally rather wrinkled or verrucose, prothallus usually indistinct, marginal, greyish-arachnoid. Surface subarachnoid or granular-furfuraceous. Apothecia rounded, at first innate, soon superfical and adnate 0.2-1.5 mm diam., solitary to 2-4-confluent, disc black, plane to convex, often white-pruinose, margin thin, ± persistent, concolorous with disc, frequently surrounded by a superficial thalline margin, concolorous with thallus. Hypothecium red-brown. Hymenium brown and granular in upper part, colourless below. Epithecium black-brown. Paraphyses ± distinct, branched, septate, swollen, capitate, brownish at apices. Asci clavate. Ascospores brown, oblong-ellipsoid to somewhat fabiform, usually 3-septate (to 5-sepate or submuriform), 17-18.7 × 6-8(-8.3) µm.
N: Sine loco (Colenso, BM). S: Canterbury (Weka pass, Flock Hill, Castle Hill). On limestone rocks.
Cosmopolitan
