维基百科 Sphaerium is a genus of very small freshwater clams, aquatic bivalve mollusks in the family Sphaeriidae, known as the fingernail clams. The small clams in this genus are unusual in that many of them, such as Sphaerium corneum, can climb around underwater on aquatic plants, using their long and strong foot. Species[edit] Subgenus Sphaerium Scopoli, 1777 Sphaerium corneum (Linnaeus, 1758) - European fingernail clam Subgenus Nucleocyclas Alimov & Starobogatov, 1968 Sphaerium nucleus (Studer, 1820) Sphaerium ovale (A. Férussac, 1807) Subgenus Parasphaerium Alimov & Starobogatov, 1968 Sphaerium nitidum Clessin, 1876 - Arctic fingernail clam Subgenus Amesoda Rafinesque, 1820 Sphaerium rivicola (Lamarck, 1818) Subgenus Cyrenastrum Bourguignat, 1854 Sphaerium solidum (Normand, 1844) Without subgenus Sphaerium asiaticum (Martens, 1864) Sphaerium bequaerti (Dautzenberg & Germain, 1914) - data deficient (DD)[1] Sphaerium cornuta Sphaerium novaezelandiae Deshayes, 1854 Sphaerium stuhlmanni Martens, 1897 - data deficient (DD)[2] Extinct ?Sphaerium beckmani Russell, 1976 [3]