Anamorph: not known.
Teleomorph: ascomata apothecia, (200–) 300–550 µm diam, discoid, hardly stipitate, black, not pruinose, surrounded by a narrow dark reddish brown to black excipular layer. Ascomatal wall composed of a lower layer of thin-walled dark brown angular cells, merging into a pad-like structure of very thick-walled and apparently gelatinized cells with reduced lumina, the outer part surrounding the hymenium composed of irregular thick-walled intertwined hyphae immersed in a gelatinous matrix. Hymenium 50–70 µm tall. Interascal tissue composed of hyaline paraphyses 2–2.5 µm diam, sparsely branched towards the slightly swollen apex, covered in a thick J+ gelatinous coat and with a reddish brown epithecial layer. Asci 44–54 × 8.5–12 µm, cylindric-clavate, short-stalked, fairly thick-walled but not fissitunicate, without an apical pore, 8-spored, covered in a thick J+ gelatinous layer. Ascospores arranged biseriately, (9–) 11.5–12.5 (–16) × 3.5–4.5 µm, ± cylindrical with rounded ends, dark brown when mature, rather thick-walled, smooth, often slightly constricted at the ± median primary septum and usually with two further septa developing closer to the primary septum than the ascospore apex, without a gelatinous sheath or appendages.
Assessed by Woods & Coppins (2012) as of Least Concern, but listed as Nationally Scarce.
Sclerococcum parellarium also occurs on Ochrolechia, but has ascospores that mostly one-septate.
On thalli and apothecia of Ochrolechia species, also reported on Pertusaria s.l. (Lepra and Pertusaria).
Widespread in western Britain, scattered elsewhere.