appendicularia

from WordNet (r) 3.0 (2006)

appendicularia
    n 1: free-swimming tadpole-shaped pelagic tunicate resembling
         larvae of other tunicates

from The Collaborative International Dictionary of English v.0.48

Appendicularia \Ap`pen*dic`u*la"ri*a\, n. [NL.] (Zool.)
   A genus of small free-swimming Tunicata, shaped somewhat like
   a tadpole, and remarkable for resemblances to the larv[ae] of
   other Tunicata. It is the type of the order Copelata or
   Larvalia. See Illustration in Appendix.
   [1913 Webster]