Green-gilled lepiota

Description:

A widespread mushroom, highly poisonous and producing severe gastrointestinal symptoms of vomiting and diarrhea, it is commonly confused with the shaggy parasol, and is the most commonly consumed poisonous mushroom in North America. Its large imposing appearance and similarity to the edible Parasol mushroom, as well as its habit of growing in areas near human habitation, are reasons cited for this. The nature of the poisoning is predominantly gastrointestinal.

Notes:

The largest of these mushrooms growing in our grass was dinner plate sized!