The particular design of muscles and bones in the neck and limbs of the turtle allow that it can draw in its exposed parts such that an attacker can find nothing but hardshell to bite.
海龟颈部和四肢的肌肉及骨骼的特殊设计使它能把暴露在外的部分缩回去，这样攻击者只能去咬坚硬的外壳。
2
Some of these coats are hard—like the shell of a nut—for extra protection.