carapace

cara|pace /k'ærəpeɪs/ (carapaces)
1 [N-COUNT]
A carapace is the protective shell on the back of some animals such as tortoises or crabs. (FORMAL)
2 [N-COUNT] usu with supp
You can refer to an attitude that someone has in order to protect themselves as their carapace. (LITERARY)
The arrogance became his protective carapace.