Circinaria hoffmanniana
General description:
As Circinaria contorta, but darker grey, thinner, scabrid or somewhat pruinose, with an effuse margin and with prominent apothecia. The areoles are flat and pressed together at the margin, unlike C. contorta which has distinctive separated, circular, convex areoles at the thallus perimeter.
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Conservation status:
Very unlikely to be threatened, but treated as Data Deficient by Woods & Coppins (2012) due to confusion in the past with Circinaria calcarea.
Distribution:
Common in southern England and Wales, apparently becoming more scattered further north.
Habitat:
On soft limestones, and cement in urban areas. Tolerant of nutrient enrichment.
Notes:
Description adapted from Fletcher et al. (2009)