What is "mussel shrimp"

Ostracoda \Os*trac"o*da\, prop. n. pl. (Zo["o]l.) An order of Entomostraca possessing shrimplike bodies enclosed in hard bivalve shells; called also seed shrimp and mussel shrimp. They were formerly referred to as Ostracoidea. They are of small size, and swim freely about; many are less than 1 mm in length. Microfossils of certain extinct orders have been found extending back to the Cambrian age.

n. tiny marine and freshwater crustaceans with a shrimp-like body enclosed in a bivalve shell [syn: seed shrimp, ostracod]