Domain: Eukarya
Kingdom: Fungi
Phylum: Basidiomycota
Class: Agaricomycetes
Order: Agaricales
Family: Psathyrellaceae

Psathyrella is a large genus of about 400 fungi, and is similar to the genera Coprinellus, Coprinopsis, Coprinus and Panaeolus, usually with a thin cap and white or yellowish white hollow stem. But the caps do not self digest as do those of Coprinellus and Coprinopsis. Some also have brown spores rather than black.

These fungi are often drab-colored, difficult to identify, and inedible, and so they are sometimes considered uninteresting. However they are quite common and can occur at times when there are few other mushrooms to be seen. The first report of a gilled mushroom fruiting underwater is Psathyrella aquatica.

Wikipedia