Panaeolus semiovatus

"Panaeolus semiovatus" var. "semiovatus", also known as "Panaeolus semiovatus" and "Anellaria separata", is a medium-sized buff colored mushroom/toadstool that grows on horse dung, and has black spores. While some guides list this species as edible, a few people experience gastric upset after consumption. Its common names are the shiny mottlegill, or egghead mottlegill.