Subphylum Mandibulata
Most of them have three pairs of walking legs, mandibles, compound eyes, antennas, some with wings. There are four classes.
Crustacea - aquatic with crusty exoskeleton, gills
Insecta - Commonly found with 3 pairs of legs, wings at some time in life cycle, body divided into three parts, mouth parts are specialised
Phylum Onychophora : (70 species, Peripatus) Possessing both annelid and arthropod characteristics.
Phylum Brachiopoda : (250 species)