Potamilus fragilis, previously Leptodea fragilis, the fragile papershell, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.

[3] Its light-shelled morphology suggests an adaptation to deep water within lakes.

[3] This species is found in the United States and Canada.

Its natural habitats include streams, rivers and freshwater embayments.

[1] A common host for the glochidia of this species is the freshwater drum (Aplodinotus grunniens).