{ ‖ } n.. (Anat.) A membranous appendage of the embryos of mammals, birds, and reptiles, -- in mammals serving to connect the fetus with the parent; the urinary vesicle. [ 1913 Webster ]

{ } a. [ Gr. &unr_; shaped like a sausage; &unr_; sausage + e'i^dos form. ] (Anat.) Of or pertaining to the allantois. [ 1913 Webster ]

‖n. pl. [ NL. ] (Zool.) The division of Vertebrata in which the embryo develops an allantois. It includes reptiles, birds, and mammals. [ 1913 Webster ]

‖n. pl. [ Gr. 'an priv. + E. allantoidea. ] (Zool.) The division of Vertebrata in which no allantois is developed. It includes amphibians, fishes, and lower forms. [ 1913 Webster ]