Description: Known only from County Fermanagh, this rare species grows on the thallus of Placidium lachneum (syn. Catapyrenium lachneum). Like M. discrepans (described elsewhere) the spores lack a perispore. In M. nigritellum the spores are muriform and far larger (15–25µm long), with between 8 and 24 cells.

Key Identification Features:

• Grows on the thallus of Placidium lachneum, rare
• Spores muriform with 8–24 cells; perispore absent.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Merismatium nigritellum at iNaturalist World Species Observations database.