Thallus greenish grey, in small patches, smooth and effuse, very thin.
Anamorph: not known.
Teleomorph: ascomata apothecia, 0.15-0.25 (-0.3) mm diam., scattered to clustered, greyish brown, sessile, concave, constricted at the base. Excipulum olive-greyish brown, well developed. Hymenium 50-60 µm tall. Epithecium hyaline to pale olive-brown. Hypothecium hyaline. Interascal tissue of unbranched paraphyses ca 1.5 µm diam., somewhat inflated at the apices. Asci 45-55 x 10-15 µm, 8-spored. Ascospores 13-15.5 x 6-7 µm [10–15 x 4–6 µm fide van den Boom & Vezda 1995], narrowly ellipsoidal, submuriform, with 3-4 transverse septa and (0–)1–2(–4) longitudinal septa.
Not formally assessed. Only recorded from a single site in GB&I, but the lichen is inconspicuous and possibly under-recorded.
Differs from Gyalidea hyalinescens var. hyalinescens in having smaller apothecia, 0.15–0.25 (–0.3) mm diam. and submuriform ascospores with 3-4 transsepta and (0–)1–2(–4) longisepta, 10–15 x 4–6 µm. The young apothecia have a greenish grey upper part to the margin, but this fades as the apothecia expand.
Probably worthy of species rank on account of its apothecial size combined with muriform ascospores.
Recorded from VC19 N Essex.
Found on the horizontal surface of a stack of bricks.