Cladocera
Cladocera , noun, plural
[New Latin, from Greek {not transcribed} a sprout + {not transcribed} a horn.]
(Zoology) An order of the Entomostraca.
They have a bivalve shell, covering the body but not the head, and from four to six pairs of legs and two pairs of antena, for use in swimming. They mostly inhabit fresh water.