si·re·ni·an /saɪˈriniən/
  (a.)海牛類
  Si·re·ni·an n. Zool. Any species of Sirenia.
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  sirenian
       n : any of two families of large herbivorous aquatic mammals
           with paddle-shaped tails and flipper-like forelimbs and
           no hind limbs [syn: sea cow, sirenian mammal]