phalaenarum is a common and widely distributed medium-sized grey mushroom that grows on dung.

The binomial Panaeolus antillarum that previously referred to a closely related species, is now reduced to synonymy with Panaeolus semiovatus var.

phalaenarum is a medium-sized mushroom which has a cap that is 2 to 4 cm, convex, and is white to yellowish.

Often mistaken for its larger cousin Panaeolus semiovatus var.

semiovatus, from which it differs in being more slender and having no annulus (ring).