noun
Biological term for the soft outer body wall of mollusks and some other invertebrates.
貝の外套膜は殻を形成する役割を持つ。
The mantle of a shellfish plays a role in forming the shell.
Compound of 外套 (がいとう, 'overcoat') + 膜 (まく, 'membrane'), referring to the cloak-like body wall of certain invertebrates.