Type. UNITED STATES. Massachusetts, Bristol Co., New Bedford, 1870, Willey 488 (FH-00377321, lectotype selected in Perlmutter et al. 2015)

Description (emended). Lichenized fungus. 

Thallus crustose, thin to endoperidermal, pale to tan, or ± shiny stain, continuous, sometimes with a dark prothallus and/or contact lines; vegetative diaspores absent. Thallus anatomy homoimerous (not stratified; photobiont throughout); photobiont: Trentepohlia alga, endoperidermal.  

Ascomata opegraphoid, scattered to clustered, elliptical to elongate, mostly short black lirellae, 0.2–1.3 x 0.2–0.3 mm, prominent to sessile, straight to curved, usually unbranched but some may have short branches. Disk closed to open, opening in water, blackish brown, epruinose; exciple carbonized, lateral and extending into the substratum, thickened basally, lined apically and proximally with melanized cells in some specimens; epithecium brown to dark brown or absent; hymenium hyaline to brownish, 58–68(2100) mm, gel-like, the gel and brownish coloration dissolving in K, K/I+ pale blue; hypothecium pale tan to orangish brown; paraphyses unbranched, thickened with darkened, swollen tips.

Asci clavate, 8-spored. Ascospores hyaline to light brownish when mature 2-celled, septum slightly constricted or not, one cell often larger, wall smooth or warty, 10-26 x 5-13 μm; pycnidia not seen.

Chemistry. Spot tests: UV+ yellowish K-, C-, KC-, PD-; secondary metabolites not detected.

Substrate and Habitat. Smooth bark of hardwood trees in shaded forests.

Distribution. Eastern North America; in North Carolina in Piedmont, Blue Ridge provinces.

Notes. Melaspilea demissa appears morphologically similar to Opegrapha s. lat., but is distinct by the brownish, 2-celled spores.