甲壳动物包被腹部各节背面及两侧的甲壳。节肢动物各体节腹面外骨骼或其总称
The text refers to the shell of crustaceans that covers the dorsal and lateral parts of each segment of the abdomen. It also refers to the exoskeleton on the ventral side of each body segment of arthropods, or the term for it in general.