Squid and octopus, which are known as cephalopods , do not have a hard outer shell. Rather, they have a single thin internal shell called a pen or cuttlebone.

• （乌贼和章鱼，它是著名的头足类，没有一个硬外壳。相反，它们有一个单一的薄壳体内部所谓的羽状壳乌贼的壳质的内壳或海螵蛸）