Psathyrella rugocephala

Scientific name:  Psathyrella rugocephala (Atkinson) Smith
Derivation of name:  Rug- means "wrinkle" and cephal-
means "head." Rugocephala aptly describes the cap of this
species.
Synonyms:  
Common name(s):  Corrugated-cap Psathyrella.
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Coprinaceae
Occurrence on wood substrate:  Saprobic; scattered or in
groups on and around decaying deciduous wood; July through
September.  
Dimensions:  Caps 5-10 cm wide; stipes 7.5-12.5 cm long and
0.5-1 cm thick.   
Cap: Brownish to rusty brown, fading to tannish; surface
coarsely radially wrinkled.  
Gills: Attached; whitish, becoming purplish-brown to black at
maturity.
Spore print: Purple-brown.
Stipe: Whitish, darkening to brownish below.
Veil: Fibrillose-membranous, not leaving a ring.
Edibility: Edible but not recommended due to difficulties in
identification.
Comments: Macroscopically, Psathyrella delineata is nearly
identical to Psathyrella rugocephala. The two species can
only be reliably separated on spore size and morphology.

More information at MushroomExpert.com: 

    

Figure 1. The browish, wrinkled cap is an important first
step in identifying Psathyrella rugocephala. Photo ©
John Plischke III.

Figure 2. Psathyrella delineata strongly resembles
P. rugocephala. Reliable separation of the two species
requires examination of spore size and morphology.
Photo © William Roody.