Plicatulidae  The Plicatulidae are a family of saltwater clams, marine bivalve mollusks, known commonly as kitten's paws or kittenpaws. These bivalves are related to oysters and scallops. The family has a single living genus, "Plicatula", with a second, "Harpax" known from fossils. Plicatulidae are small, with weakly convex shells which are irregularly oval or even almost triangular. Typically, they attach themselves to a hard surface by the right valve. The ligament is internal and triangular.