Phyllotopsis nidulans

Scientific name:  Phyllotopsis nidulans (Pers.) Singer
Derivation of name: Phyllo- means "leaf" (or "gill" in the
case of mushrooms) and opsis means "appearance" in
reference to the showy, prominent gills. Nid- means
"nest" although it is not clear how nest or nesting applies
to this species.
Synonyms:  Pleurotus nidulans (Pers.) P. Kumm.
Common name(s):  Orange mock oyster.
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Tricholomataceae
Occurrence on wood substrate:  Saprobic; solitary or
more typically in overlapping clusters on conifer and
deciduous wood; August through November.  
Dimensions: Caps 2.5-7.5 cm wide.   
Cap:  Orange to yellow-orange or paler; densely covered
with hairs; dry; odor offensive.     
Gills: Orange to yellow-orange; radiating from point of
attachment.
Spore print: Pale pink.
Stipe: Absent.
Veil: Absent.
Edibility: Inedible.
Comments: A very distinctive fungus but usually with a very
nasty smell.

More infromation at MushroomExpert.com:   

Figure 1. A beautiful view of orange mock oyster with rays
of sunlight highlighting the fuzzy caps. Photo © Larry Grand.

Figure 2. A much paler specimen than that in Figure 1.
Photo © William Roody.

Figure 3. Very young and very fuzzy caps. Photo © Gary
Emberger.

Figure 4. Gills of a young specimen. The gills have the same
color range as the cap surfaces. Photo © R. Al Simpson.

Figure 5. Gills radiate from the stalkless points of
attachment. Photo © Gary Emberger.

Figure 6. This is an interesting group of young and
maturing specimens. What appears to be a stalk on
the large specimen on the right is actually a young,
fuzzy cap oriented vertically. Photo © Pam Kaminski.