Marasmius sullivantii 

Marasmius sullivantii Mont. 1856

Marasmius sullivantii has a reddish-orange to rust-brown dry, white close, narrow gills that are attached to free, and a stiff, glabrous stem that is initially off-white to cream becoming reddish-orange to blackish especially toward the baser over time. It is a saprotrophic mushroom that grows in leaf debris of broadleaf forests during the summer months.  

Marasmius sullivantii is in the Marasmiaceae family of the Agaricales order.