Returning from a walk this morning, I spotted a mushroom growing in the front of the house. It was about 5 inches high (12 cm). The top of the cap was a creamy white color with small scales. I turned it over to observe the underside of the mushroom cap. The gills were free from the stalk, thin, and tightly packed. An annulus (ring) was present.
I brought it into the house, took off the cap and placed it gill-side down on a piece of white paper. After several hours, I removed the cap to observe the spore print. The spores were green as I expected. The cap had discolored to a tan color with a slightly green tint.
Using my Mushrooms & Other Fungi of the MidContinental United States book by Huffman, Tiffany and Knaphus, I followed the key to confirm that this was a Chlorophyllum molybdites. The mushroom is common in this area often growing in fairy rings in gardens. The book provided the following information.
A fairy ring is a striking phenomenon in itself but closer inspection reveals another interesting characteristic. a bank of lighter green grass is found outside the ring of mushrooms and a ring of lush, dark green grass occurs inside the ring. the mycelium of the fungus is growing vigorously in advance of the ring of fruiting bodies, using soil nitrogen and other nutrients in its assimilation of cellulose. Behind the ring the mycelium is dying and the nitrogen and other nutrients are leased. They are quickly used by the grass.
The mushroom may not be poisonous to all people but may cause severe illness in some.