Lentinellus ursinus

Scientific name:   Lentinellus ursinus (Fr.) Kuhner
Derivation of name: Urs- means "bear" in reference to
the hairy brown cap.  
Synonyms:  Lentinus ursinus Fr.
Common name(s):  Bear Lentinus.
Phylum:   Basidiomycota
Order:   Russulales
Family:   Auriscalpiaceae
Occurrence on wood substrate: Saprobic; solitary to
more often in groups and overlapping clusters on decaying
deciduous wood and sometimes conifer wood; summer
through fall.   
Dimensions:  Caps 2.5-10 cm wide.  
Cap: Reddish brown, paler toward the margin; surface
covered with dark brown hairs especially toward the base.
Gills: Whitish to pinkish-brown; radiating from point of
attachment to substrate; edges coarsely serrated, irregularly
torn.
Spore print: White.
Stipe: Absent.
Veil: Absent.
Edibility: Inedible, bitter.
Comments: The presence of amyloid spores distinguishes
this genus from Lentinus.

More information at MushroomExpert.com:   

Figure 1. Overlapping clusters of Bear Lentinus on
wood. Photo © Larry Grand.
    

Figure 2. Lentinellus ursinus. Photo © George
Barron.

Figure 3. Here and in Figure 1. note that the cap margins are
often lobed. Photo © William Roody.

Figure 4. Serrate gill edges and torn gills are characteristic of
Lentinellus ursinus.

Figure 5. Lentinellus ursinus as it might appear on the
collection tables during a foray.