Cladocera

Cladocera, a subdivision of the Phyllopoda, which is itself one of the four groups included in the Entomostraca. The Phyllopoda include those elongated, segmented Entomostraca, which have a shield-shaped or bivalve shell. The Cladocera includes those Phyllopods which are small and laterally compressed and have a bivalve shell and a pair of large, two-branched swimming feet. The most typical and best-known genus is Daphnia, the "water flea."