The Walnut Mycena (Mycena crocea) is a decomposer of Walnut and Hickory shells and can be found from late summer through fall. It is distributed east of the Rocky Mountains in North America and can be found in wooded settings composed of Walnut (Juglans sp.) and/or Hickory (Carya) trees.

M. crocea is colored distinctly orange to yellow. It is easily distinguished by its color and habit of growing on buried nut shells. The gills are color whitish to yellowish. The gill attachment is attached to the stem or creating an "S"-like loop on attachment to the stem (sinuate). The stem is much longer than the width of the cap with white basal mycelium. The spore print is white.

The terminal ends of the mycelium on the mushroom's gills are quite unique. Below is a video tour of these structures.