Crucibulum laeve

Scientific name:  Crucibulum laeve (Huds.) Kambly
Derivation of name:  Laev- means "smooth" referring
to the inner nest wall.
Synonyms: Crucibulum vulgare Tul. & C. Tul.  
Common name(s):  White-egg bird's nest; Common bird's
nest.
Phylum:   Basidiomycota
Order:   Agaricales
Family:   Nidulariaceae
Occurrence on wood substrate: Saprobic; typically
clustered on wood chips, bark, fallen branches; summer
through fall.    
Dimensions:  Nests are 0.5 to 1 cm tall and wide.  
Sterile nest surfaces: The tawny-yellow, velvety lid is
conspicuous when the nests are young. The inside of the
cup-like nest is white, smooth and shiny. There are no
tooth-like projections on the rim of the nest.
Fertile tissue: The eggs (peridioles) are about 1.5-2 mm
wide, white, and attached to the cup by a long thin cord.
Edibility: One simply does not eat things such as this.
Comments: This is the only bird's nest fungus with white
peridioles in our range.

More information at MushroomExpert.com:  


Figure 1.  These fungi are small. There are a number of
specimens growing on the hardwood mulch of this
landscape bed. The toothpick is for scale.

Figure 2. Up close, these fungi are quite unmistakable.
The tawny-yellow membrane of young specimens breaks
open to reveal the white peridioles ("eggs") within.
Photo © Fred Habegger

Figure 3. Intact membranes of young specimens.

Figure 4. The same specimens as in Figure 3 but the
membrane has been ruptured with the toothpick in order to
uncover the eggs.

Figure 5. The smooth and unfurrowed (nonstriate) inner walls
of the nests are clearly seen in the empty nest and nests with
eggs.

Figure 6. Here, an egg was taken out of the nest.
A portion of the cord (funiculus) is visible.