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 The bivalves or clams are dwellers of fresh, marine or brackish waters. They lack a head and are without jaws or radular teeth; they are protected by a pair of shelly valves which are connected or hinged by a horny ligament and which are moved by the contraction of one to three muscles attached to the inner sides of the valves; feeding is usually done with the aid of their ciliated or hair-covered gills. Further details have been presented in the chapter on "The Life of the Clam." The class is also known as Lamellibranchia, Bivalvia or Acephala. The class may be divided into the following orders and suborders:

Order PALAEOCONCHA


 * Suborder SOLEMYACEA (Awning Clams)

Order PROTOBRANCHIA


 * Suborder NUCULACEA (Nut Clams)

Order FILIBRANCHIA


 * Suborder TAXODONTA (Ark Shells)


 * Suborder ANISOMYARIA (Scallops, Oysters, Sea Mussels)

Order EULAMELLIBRANCHIA


 * Suborder SCHIZODONTA (River Mussels)


 * Suborder HETERODONTA (Cockles, Lucines, Venus)


 * Suborder ADAPEDONTA (Mya and Razor Clams, Teredos)


 * Suborder ANOMALODESMACEA (Pandora Clams)

Order SEPTIBRANCHIA


 * Suborder POROMYACEA (Dipper Clams, Meat Eaters)