Kingdom: Fungi
Division: Basidiomycota
Class: Agaricomycetes
Order: Agaricales
Family: Strophariaceae
Genus: Agrocybe
Species: A. praecox
Binomial name: Agrocybe praecox
Synonyms: Agaricus acericola, Pholiota acericola.
Common names: Spring field cap, Spring Agaric, Maple Agrocybe

Agrocybe praecox is an early-fruiting mushroom appearing late spring and is recognized by a tan-brown to biscuit brown, smooth to cracked in dry weather, sometimes appendiculate cap (3-6 cm broad), closed gills, and tendency to have pallid rhizomorphs (root-forms) at the base.
It is a variable fungus emerging from areas that have been spread with wood chips used in landscaping.

Agrocybe praecox is one of a complex group of fungi that are very difficult to separate in the field. Note: In some field guides this mushroom is recorded in the family Bolbitiaceae. 

Agrocybe praecox.JPG 

Agrocybe praecox-002.JPG 

A cap which has cracked in dry weather
Agrocybe praecox-007.JPG

Agrocybe praecox-003.JPG 

Agrocybe praecox-001.JPG

Thanks to Wikipedia for text and information: