The Collaborative International Dictionary of English v.0.48:

Sipunculacea \Si*pun`cu*la"ce*a\, n. pl. [NL., from Sipunculus,
   the typical genus. See Siphuncle.] (Zool.)
   A suborder of Gephyrea, including those which have the body
   unarmed and the intestine opening anteriorly.
   [1913 Webster]