
Pisidium is a genus of very small or minute freshwater clams known as pill clams or pea clams, aquatic bivalve molluscs in the family Sphaeriidae, the pea clams and fingernail clams.

Pisidium amnicum is a species of very small freshwater clam, sometimes known as the greater European peaclam or the River pea shell. It is an aquatic bivalve in the family Sphaeriidae.

Pisidium casertanum, the pea cockle or pea clam, is a minute freshwater bivalve mollusc of the family Sphaeriidae.

Pisidium clessini is a species of extinct freshwater bivalve from family Sphaeriidae.

Pisidium conventus, the arctic-alpine pea clam, is a species of freshwater bivalve from the family Sphaeriidae.

Pisidium henslowanum is a species of very small freshwater clam or pea clam, an aquatic bivalve mollusc in the family Sphaeriidae. It is commonly referred to as the Henslow peaclam.

Pisidium hibernicum is a species of freshwater bivalve from the family Sphaeriidae.

Pisidium lilljeborgii is a species of freshwater bivalve from the family Sphaeriidae.

Pisidium milium is a species of very small freshwater bivalve in the family Sphaeriidae, the fingernail clams and pea clams.

Pisidium nitidum, the shining pea clam, is a species of minute freshwater clam, an aquatic bivalve mollusc in the family Sphaeriidae, the pea clams and fingernail clams.

Pisidium obtusale is a species of freshwater bivalve from family Sphaeriidae.

Pisidium pseudosphaerium is a species of freshwater bivalve from family Sphaeriidae.

Pisidium pulchellum, the iridescent pea mussel, is a minute species of pea clam, a freshwater bivalve in the family Sphaeriidae.

Pisidium punctiferum, the striate peaclam, is a freshwater bivalve of the family Sphaeriidae.

Pisidium subtruncatum is a species of pill clam, a minute freshwater bivalve in the family Sphaeriidae.