Megacollybia platyphylla

Scientific name:  Megacollybia platyphylla (Persoon:Fries)
Kotlaba and Pouzar
Derivation of name: Platy- means "broad" or "wide" and
phyll- means "leaf" or "leaves" referring to the gills.
Platyphylla means "broad-gilled."
Synonyms:  Tricholomopsis platyphylla (Pers.) Singer;
Collybia platyphylla Fr.
Common name(s):  Broad gill; Platterful mushroom.
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Tricholomataceae
Occurrence on wood substrate:  Saprobic; solitary to
several on and near deciduous logs, stumps, wood debris or
on ground from buried wood; May through October.  
Dimensions:  Caps 5-12.5 cm wide and stipes 7.5-12.5
cm long and 1-2 cm thick.  
Cap:  Smooth; brownish-gray caps; radially streaked with
dark fibers.      
Gills: Attached; white; broad; edges uneven to ragged,
appearing eroded.
Spore print:White.
Stipe:White, smooth, with white rhizomorphs present at the
base.
Veil: Absent.
Edibility: Edible.
Comments: One of the first large mushrooms to appear in
the spring.

More information at MushroomExpert.com:   


Figure 1. A group of platterful mushrooms arising from a
stump. Photo © William Roody.

    

Figure 2. This young specimen is oozing water from the
stipe. The gill edges are even. A white rhizomorph is visible
to the left of the stalk base.

Figure 3. Caps sometimes crack or split when drying out.

Figure 4. Caps of Megacollybia platyphylla are streaked
with dark, radial fibers.

Figure 5. The gill edges of this mature specimen are quite
ragged. Compare to the gills visible in Figure 2.