A common fungus on enriched soils especially with herbivore dung. The partial veil remnants on the cap-edge provides the common name 'pettycoat'. The cap changes shape as it matures.

References: 
Breitenbach, J. & Kranzlin, F. (1995) Fungi of Switzerland, Volume 4, Agarics, 2nd Part.
Wood, E. & Dunkelman, J. (2017) Grassland Fungi: a field guide.
O'Reilly, P. (2016) Fascinated by Fungi.