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Sphaerium corneum.jpg
Four shells of Sphaerium corneum. Scale bar is in mm
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Subclass: Heterodonta
Order: Veneroida
Suborder: Sphaeriacea
Family: Sphaeriidae
Deshayes, 1855 (1820)

Cycladidae, Rafinesque 1820[1][2]

The Sphaeriidae are a family of small to minute freshwater bivalve molluscs, in the order Veneroida; this family also includes the clams formerly placed in the Pisidiidae. In the US, they are commonly known as pea clams or fingernail clams.[3][4]


Genera in the family Sphaeriidae include:

Biology and ecology[edit]

Sphaeriidae are hermaphrodites with internal fertilization. Developing young are incubated within their mother (ovoviviparity), and newborn clams look like miniature copies of the adults.[4]

Parasites and/or predators include the Sciomyzidae.


  1. ^ Bowden, John & Heppell, David (1968). "Revised list of British Mollusca. 2. Unionacea-Cardiacea" (PDF). Journal of Conchology. 26 (4): 237–272, note 55, pages 253–254. Archived (PDF) from the original on 28 December 2014. 
  2. ^ Baker, Horace Burrington (1964). "Notes on Sphaeriid Names". The Nautilus. 78 (2): 45–47. 
  3. ^ Heard, William H. 1965. Comparative life histories of North American pill clams (Sphaeriidae: Pisidium). Malacologia, 2: 381-411.
  4. ^ a b Heard, William H. 1977. Reproduction of fingernail clams (Sphaeriidae: Sphaerium and Musculium). Malacologia, 16: 421-455.