Exoskeleton

An exoskeleton (from Greek ἔξω, éxō "outer" and σκελετός, skeletos "skeleton") is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton (endoskeleton) of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells".

Among the species that have skeletons and have members who are Union Citizens, only about 5% have only Exoskeletons, and about 15% have both endoskeletons and exoskeletons with the remaining 80% having only endoskeletons.

For more, see the Wikipedia article on Exoskeleton.