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Mammalia

(Science: zoology) 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.

mammalia are divided into three subclasses;

i. Placentalia. This subclass embraces all the higher orders, including man. In these the foetus is attached to the uterus by a placenta.

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.

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.

Origin: NL, from L. Mammalis. See mammal.