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(Map updated: 11 August 2009)

The grey thallus of this species grows on calcareous rock forming pits (0.3–0.5mm diam.) at the surface in which the spherical discs or perithecia are immersed. The spore sacs or asci contain eight colourless spores (25–50µm long) with three to four transverse partitions (septa) and one to two longitudinal septa. There is currently some doubt over whether this species is distinct from Thelidium incavatum.

Key characteristics

• A ‘dots on limestone’ species; sunken discs in pits lacking a black, protective outer layer (involucrellum)
• Spores: colourless, 8/ascus, transverse and longitudinal septa present (submuriform); hard and soft limestones.

NBN Atlas mapping: Species account : NBN Atlas UK Species Observations database

iNaturalist: Species account : iNaturalist World Species Observations database

Original text submitted by Vince J. Giavarini