They are small crustaceans , typically around 1 mm ( 0.039 in ) in size , but varying from 0.2 to 30 mm ( 0.0079 to 1.1811 in ) in the case of Gigantocypris .
Ostracods are small crustaceans , typically around 1 millimetre ( 0.04 in ) in size , but varying from 0.2 millimetres ( 0.0079 in ) to 30 mm ( 1.2 in ) in the case of Gigantocypris .