A subclass of Mammalia, having a cloaca where ducts of this urinary, genital, and alimentary systems terminate, such as birds. The feminine lays eggs like a bird. See Duck mole, under duck, and echidna.
In mammalogy, the lowest purchase of this class Mammalia, containing those animals which may have a single or typical orifice associated with genital, urinary, and digestion body organs, and therefore are oviparous.
In conchology, a division of geophilous pulmonate gastropods, obtaining the outside male and feminine orifices contiguous or common: against Ditremata.