Cladocera

from The Collaborative International Dictionary of English v.0.48

Cladocera \Cla*doc"e*ra\, n. pl. [NL., fr. Gr. ? a sprout + ? a
   horn.] (Zool.)
   An order of the Entomostraca.
   [1913 Webster]

   Note: They have a bivalve shell, covering the body but not
         the head, and from four to six pairs of legs and two
         pairs of anten[ae], for use in swimming. They mostly
         inhabit fresh water.
         [1913 Webster]