Malacostraca
plural noun
Mal·a·cos·tra·ca
ˌmaləˈkästrəkə
: a major subclass of Crustacea including most of the well-known marine, freshwater, and terrestrial members of the group (as lobsters, crabs, shrimps, sow bugs, beach fleas)
malacostracan
¦⸗⸗¦kästrəkən 
adjective or noun malacostracous adjective
-kəs
Word History
Etymology
New Latin, from Greek malakostraka, neuter plural of malakostrakos soft-shelled, from malak- malac- + -ostrakos (from ostrakon shell)
First Known Use
1819, in the meaning defined above