Phylum: Basidiomycota Family: Agaricaceae
Panaeolus subfirmus P. Karst.
Very similar to Panaeolus acuminatus but with larger spores and preferring heavily manured pasture. Not often recorded in Britain, having a more northern distribution
References:
Knudsen & Vesterholt (2012 second edition) - Funga Nordica
Doveri - Fungi Fimicoli Italici