\Ce*ta"ce*a\, n. pl. [NL., from L. cetus whale, Gr. ?.]
(Zo["o]l.)
An order of marine mammals, including the whales. Like
ordinary mammals they breathe by means of lungs, and bring
forth living young which they suckle for some time. The
anterior limbs are changed to paddles; the tail flukes are
horizontal. There are two living suborders:
(a) The {Mysticete} or whalebone whales, having no true teeth
    after birth, but with a series of plates of whalebone
    [see {Baleen}.] hanging down from the upper jaw on each
    side, thus making a strainer, through which they receive
    the small animals upon which they feed.
(b) The {Denticete}, including the dolphins and sperm whale,
    which have teeth. Another suborder ({Zeuglodontia}) is
    extinct. The {Sirenia} were formerly included in the
    Cetacea, but are now made a separate order.