A specimen of crustose lichen collected on Mont Saint-Hilaire (regional county municipality of La Vallée-du-Richelieu, Québec) in 1996 and initially identified as Bacidia schweinitzii, was recently reidentified as being the poplar dot lichen (Arthrosporum populorum). This represents a new species and genus for the province. The population was rediscovered during fieldwork conducted in 2013.