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Monotremata 单孔目 单孔目 Monotremata n 1: coextensive with the subclass Prototheria [synonym: {Monotremata}, {order Monotremata}] Mammalia \Mam*ma"li*a\, n. pl. [NL., from L. mammalis. See
{Mammal}.] (Zool.) The highest class of Vertebrata. The young are nourished for a time by milk, or an analogous fluid, secreted by the mammary glands of the mother. [1913 Webster] Note: Mammalia are divided into three subclasses; [1913 Webster] I. {Placentalia}. This subclass embraces all the higher orders, including man. In these the fetus is attached to the uterus by a placenta. [1913 Webster] II. {Marsupialia}. In these no placenta is formed, and the young, which are born at an early state of development, are carried for a time attached to the teats, and usually protected by a marsupial pouch. The opossum, kangaroo, wombat, and koala are examples. [1913 Webster] III. {Monotremata}. In this group, which includes the genera {Echidna} and {Ornithorhynchus}, the female lays large eggs resembling those of a bird or lizard, and the young, which are hatched like those of birds, are nourished by a watery secretion from the imperfectly developed mammae. [1913 Webster] Monotremata \Mon`o*trem"a*ta\, n. pl. [NL., fr. Gr. mo`nos single ? hole.] (Zool.) A subclass of Mammalia, having a cloaca in which the ducts of the urinary, genital, and alimentary systems terminate, as in birds. The female lays eggs like a bird. See {Duck mole}, under {Duck}, and {Echidna}. [1913 Webster]
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