Thallus superﬁcial, whitish, uneven to verrucose, thin to well-developed, up to 200 µm thick, sometimes cracked.
Anamorph: not known.
Teleomorph: ascomata perithecioid. Perithecia forming moderately projecting to rather prominent mounds 0.5-0.8 mm diam., without a thalline covering (rarely partly covered by a lumpy thalline layer in specimens with a thick thallus). Involucrellum well-developed. Asci 8-spored. Ascospores muriform, dark brown, (20.5-)28.5-36(-38.5) × (12-)15-20.5(-23.8) µm, length/width ratio (1.3-)1.6-2.2(-3.1).
Listed by Woods & Coppins (2012) as Least Concern and Nationally Scarce.
P. melaspora has rather large, prominent perithecia, a pale thallus, relatively small brown ascospores and possesses an involucrellum.
In GB&I recorded from Wales, N. England, Scotland.
On damp calcareous sandstone, mica-schist and limestone, on damp cliffs, below moist overhangs and near streams, mainly upland.