Sirenia \Si*re"ni*a\, n. pl. [NL.]

(Zo["o]l.) An order of large aquatic herbivorous mammals, including the manatee, dugong, rytina, and several fossil genera.

Note: The hind limbs are either rudimentary or wanting, and the front ones are changed to paddles. They have horny plates on the front part of the jaws, and usually flat-crowned molar teeth. The stomach is complex and the intestine long, as in other herbivorous mammals. See Cetacea
   (b) .

Source: Webster's Revised Unabridged Dictionary (1913)