The lobster has an exoskeleton.
The definition of an exoskeleton is a hard supporting structure on the outside of the body.
An example of an exoskeleton is a lobster's shell.
any hard, external, secreted supporting structure, as the shell of an oyster or the cuticle of a lobster
A hard outer structure, such as the shell of an insect or crustacean, that provides protection or support for an organism.
From exo- + skeleton.