Pyrenula hibernica
Thallus immersed, pale olive-green or yellow-buff, sometimes with white pseudocyphellae, smooth, continuous; with age becoming rougher and rarely cracked.
Anamorph: conidiomata stromatic, ca 2 mm diam., divided into chambers. Conidia 24-27 × ca 1 μm.
Teleomorph: ascomata perithecia, 1-1.2 mm diam., black, arising 1-1.5 mm below the surface; only the pale ostiole visible at the surface, or perithecia visible through translucent surface of thallus; occurring singly, or radially arranged in groups of 2 to 5. Ostioles lateral, often joined, visible as a pale yellow- or orange-brown depression, or level with surface of thallus. Asci 4- to 8-spored. Ascospores (57-) 70-135 (-140) × (24-) 26-47 (-55) μm, cylindric- to fusiform-ellipsoidal, muriform, brown when mature.
Chemistry: thallus C–, K–, KC–, Pd–, UV+ pale yellow.
Assessed by Woods & Coppins as Vulnerable (D2). It is listed as Nationally Rare, and is a (former) BAP Priority Species listed under Section 42 of the NERC Act 2006 and Section 2(4) of the NC (Scotland) Act 2004. It is a species for which the UK has International Responsibility.
NW England (Cumberland), NW Wales (Merioneth), W Scotland (Westerness, Loch Sunart, Mull), SW Ireland (Kerry, Killarney).
On smooth bark of Corylus, Ilex and Sorbus in very sheltered, moist ravines.