Melanohalea septentrionalis

Thallus forming small rosettes, 1–3 (–5) cm diam., closely appressed, occasionally with upturned lobe apices, thin; lobes 1–3 (–5) mm broad, flat to somewhat convex, discrete to overlapping with ± wavy margins; upper surface red- or dark brown, frequently pitted, shiny at the margins; pseudocyphellae small, dot-like, appearing like scattered white dots (with hand lens); lower surface pale to dark brown; rhizines unbranched, scattered, pale to dark brown. Apothecia abundant, often crowded and overlapping, covering most of the thallus apart from the extreme margin, 0.5–3 (–5) mm diam.; disc red-brown, concave when immature, becoming flat and undulating; thalline margin thin, smooth with many pseudocyphellae. Ascospores 9–13 × 5–8 μm, ellipsoidal. Conidia 5–6.5 × ca 1 μm, bacilliform. Cortex K–, N–; medulla C–, K–, KC–, Pd+ orange-red, UV– (fumarprotocetraric and protocetraric acids).

Forms small, neat, richly fertile thalli. The occurrence on Birch in Britain is unusual as it is normally reported on Grey Alder and Willow abroad. Melanelia olivacea (L.) Ach. (1803), unknown in Britain, has a more wrinkled, matt thallus, a broader more distinct marginal zone without apothecia and a crenulate thalline exciple. It has been incorrectly reported from Scotland.