box tortoise

from The Century Dictionary.

• noun A tortoise with a hinged plastron which can be so closely applied to the edge of the carapace, when the head, tail, and limbs have been drawn in, that the animal is practically boxed up in the shell; a tortoise of the family Cistudinidœ. Generally called box-turtle in the United States.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun chiefly terrestrial turtle of North America; shell can be closed tightly