malacostraca have heads with six segments. they have a pair of antennules and a pair of antennae. they also have mouthparts. there are appendages near the mouthparts, called maxillipeds. they have five pairs of walking legs. the first pair is formed like a pincer. there are eight thoracic segments. there are six abdominal segments. they are used for swimming. members of malacostraca have compound stalked or sessile eyes. they have a two-chambered stomach and a centralized nervous system.