Webster's Revised Unabridged Dictionary · 1913

marsupium

marsupium , noun

[Latin, a pouch]

(a)
(Anatomy & Zoology) The pouch, formed by a fold of the skin of the abdomen, in which marsupials carry their young; also, a pouch for similar use in other animals, as certain Crustacea.
(b)
(Anatomy & Zoology) The pecten in the eye of birds and reptiles. See Pecten.