trochosphere

from The Collaborative International Dictionary of English v.0.48

Trochosphere \Troch"o*sphere\, n. [Gr. ? a wheel + sphere.]
   (Zool.)
   A young larval form of many annelids, mollusks, and
   bryozoans, in which a circle of cilia is developed around the
   anterior end.
   [1913 Webster]