In some older classifications includes the Branchiopoda and Copepoda and Ostracoda and Cirripedia

• No longer in technical use

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Entomostraca \En`to*mos"tra*ca\, n. pl. [NL., fr. Gr. ? cut in pieces + ? burnt clay, the hard shell of Testacea.] (Zo["o]l.) One of the subclasses of Crustacea, including a large number of species, many of them minute. The group embraces several orders; ...

Wikipedia Word definitions in Wikipedia
Entomostraca is a historical subclass of crustaceans , no longer in technical use. It was originally considered one of the two major lineages of crustaceans (the other being the class Malacostraca ), combining all other classes – Branchiopoda , Cephalocarida ...