Description: This is a crustose rarity of free-draining, upland limestone surfaces. In appearance, the thallus is pale fawn to ochre-coloured, studded with tiny (0.2-0.4mm diam.) black discs. It resembles Clauzadea monticola (described elsewhere) which has simple spores, and other rare, Catillaria species, so here it is important to use the microscope to examine the internal features of the disc, especially the hypothecium. In Ireland, C. modesta is known from two sites in west Donegal.

Key Identification Features:

• Pale fawn thallus with tiny black discs; one-septate spores
• Hypothecium, dark red-brown.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Catillaria modesta at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Catillaria modesta at iNaturalist World Species Observations database.