Schizophyllum commune

Scientific name:  Schizophyllum commune Fr.
Derivation of name:  Schiz means "split" or "divide" and
phyllum means "leaf" (or "gill" in the case of mushrooms).
Commun- means "common" or "in common" referring to the
commonness of this species, found on every continent.
Synonyms:  
Common name(s):   Common split gill; Split gill.
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Schizophyllaceae
Occurrence on wood substrate:  Saprobic; solitary,
scattered or in overlapping clusters on decaying hardwoods;
year-round.
Dimensions: Caps 1-4.5 cm wide.    
Cap: White to gray; dry; densely hairy; fan to shell-shaped
in lateral attachment, saucer-shaped when centrally
attached.  
Gills: Gill-like folds are white to gray or pinkish-gray; hairy;
split lengthwise.
Spore print: White.
Stipe: Absent or simply a narrow extension of the cap.
Veil: Absent.
Edibility: Inedible.
Comments:  The fruit body can be described as a
compound structure consisting of compressed radiate
cupules. What appear to be gills are the margins of two
adjacent cupules with proliferating marginal tissue makng it
appear that the "gill" is split.
 
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Figure 1. A typical fruiting of common split gill on wood.
Photo © Larry Grand.

Figure 2. Before opening up to reveal the gills, young specimens
may resemble fuzzy white cup fungi.
Photo © Lauri Meyers.

Figure 3. Saucer-shaped appearance of centrally attached
fruitbodies.
Photo © David Work.

Figure 4. A closeup showing the many split gills of
Schizophyllum commune.
Photo © Gary Emberger.

Figure 5. The green dots indicate the "splits" where the two
margins of adjacent cupules meet.
Photo © Gary Emberger.