Pleurotus dryinus

Scientific name:  Pleurotus dryinus (Pers.) P. Kumm.
Derivation of name: Pleur- means "side" and otus means
"ear" referring to the off-center stalk or laterally attached
stipe of some species in the genus. Dry- means "oak" and
inus means "pertaining or belonging to." Oak is a common
substrate for this fungus.
Synonyms: Agaricus dryinus Pers. 
Common name(s):  Veiled oyster.
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Pleurotaceae
Occurrence on wood substrate:  Saprobic/parasitic;
solitary to several on decaying logs, stumps, and trunks of
deciduous trees, also on trunks of living trees; July through
October.  
Dimensions:  Caps 4-12 cm wide; stipes 4-10 cm long and
1-3 cm thick.   
Cap:  Dry; white to cream when young, ages with
yellowish tints or bruises yellow where damaged;
cottony-hairy, then scaly in age; veil fragments often on
margin.
Gills: Decurrent; white, becoming yellowish with age.
Spore print: White.
Stipe: Central to eccentric; whitish.
Veil: Whitish partial veil leaving membranous ring on upper
stalk. As the specimen ages, the veil may disappear making
identification less certain.
Edibility: Edible.
Comments: This is the only Pleurotus species with a veil.

More information at MushroomExpert.com:  

Figure 1. Pleurotus dryinus. Photo © John Plischke III.   

Figure 2. A collection of veiled oyster specimens. The
yellowish discoloration on the specimen on the far right
appears to be due to bruising or damage of some other
sort. Photo © Steve Nelsen.


Figure 3. Veiled oyster has decurrent gills, a ring, and an
overall white color. Photo © William Roody.