The following are some major subclasses of the class Crustacea:

(1) Subclass: Branchiopoda--fairy shrimp, brine shrimp
(2) Subclass: Copepoda--copepods
(3) Subclass: Cirripedia--barnacles
(4) Subclass: Malacostaca:

Order: Stomatopoda--mantis shrimp
Order: Euphausiacea--krill
Order: Decapoda--shrimps, lobsters, crabs