carapace, cuticle, shell - hard outer covering or case of certain organisms such as arthropods and turtles

plastron - (zoology) the part of a turtle's shell forming its underside

invertebrate - any animal lacking a backbone or notochord; the term is not used as a scientific classification

body covering - any covering for the body or a body part

skeletal system, systema skeletale, skeleton, frame - the hard structure (bones and cartilages) that provides a frame for the body of an animal