Lentinellus ursinus

Scientific name:   Lentinellus ursinus (Fr.) Kuhner
Derivation of name: Lentus means "pliable" and
"tenacious" as in chewy and ellus is the diminutive form.
Urs- means "bear" in reference to the hairy brown cap.  
Synonyms:  Lentinus ursinus (Fr.) 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: There are a number of other Lentinellus
species (e.g., Figure 8 shows Lentinellus vulpinus)
and all are too bitter to be edible. My keys include
only two of the more common and conspicuous
species: Lentinellus micheneri and Lentinellus
ursinus. The presence of amyloid spores distinguishes
Lentinellus from the genus 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. Photo © Gary Emberger.

Figure 5. At first, this seems like a typical specimen of
Lentinellus ursinus. The surprise was in the nature of the
gills. See Figure 6. Photo © Bill Bakaitis.

Figure 6. Note the gills that are somewhat poroid and the
lack of clearly serrated gill edges. The specimen in Figure 5
and 6 was photographed by Bill Bakaitis and distributed to
several mycologists who agreed that the mushroom, while
unusual, was Lentinellus ursinus. Photo © Bill Bakaitis.

Figure 7. Lentinellus ursinus as it might appear on the
collection tables during a foray. Photo © Gary Emberger.

Figure 8. This is a photograph of Lentinellus vulpinus
which resembles L. ursinus in several respects. Unlike L.
ursinus, L. vulpinus caps are attached to short, lateral
stalks that narrow downward and fuse with others to form
a common base. Photo © Steve Nelsen.