Gymnopus biformis

Gymnopus biformis is a North American species of agaric fungus in the family Omphalotaceae. The species was originally described by Charles Horton Peck in 1903 as "Marasmius biformis". The specific epithet "biformis" refers to the two distinct cap shapes, which Peck noted could be either campanulate (bell-shaped) or flattened. Roy Halling transferred the fungus to "Gymnopus" in 1997.