ems ▁up ▁to ▁ ▁long . ▁The ▁closely ▁crow ded ▁g ills ▁unders ide ▁the ▁cap ▁are ▁initially ▁yellow ▁before ▁turning ▁brown . ▁Cort in arius ▁c inn am ome us ▁is ▁common ▁in ▁d amp ▁places ▁in ▁con ifer ous ▁for ests . ▁ ▁It ▁is ▁distributed ▁throughout ▁the ▁temper ate ▁zone ▁of ▁the ▁Northern ▁Hem is phere . ▁ ▁Tax onomy ▁First ▁described ▁by ▁Carl ▁Lin na eus ▁in ▁ 1 7 5 3 ▁as ▁Ag ar icus ▁c inn am ome us , ▁the ▁fung us ▁was ▁given ▁its ▁current ▁name ▁by ▁E lias ▁Magn us ▁F ries ▁in ▁ 1 8 3 8 . ▁The ▁names ▁D erm ocy be ▁c inn am ome a ▁( M oser ), ▁Fl amm ula ▁c inn am ome a ▁( K um mer , ▁ 1 8 7 1 ) ▁and ▁G om ph os ▁c inn am ome us ▁( K unt ze , ▁ 1 8 9 8 ) ▁reflect ▁differ ing ▁approaches ▁over ▁the ▁years ▁to ▁the ▁tax onomy ▁of ▁Cort in arius ▁species . ▁The ▁m ush room ▁is ▁commonly ▁known ▁as ▁the ▁" c inn am on ▁web cap ". ▁ ▁Description ▁The ▁cap ▁is ▁quite ▁thin ly ▁f les hy , ▁ ▁in ▁diameter , ▁initially ▁quite ▁spher ical , ▁later ▁bl unt ly ▁convex ▁to ▁bell - sh aped , ▁usually ▁with ▁an ▁um bo , ▁and ▁often ▁irregular ▁and ▁bent ▁or ▁w avy ▁towards ▁the ▁margin . ▁The ▁margin ▁is ▁initially ▁cur ved