Heteropoda

from The Collaborative International Dictionary of English v.0.48

Heteropoda \Het`e*rop"o*da\, n. pl. [NL., fr. Gr. ? other +
   -poda.] (Zool.)
   An order of pelagic Gastropoda, having the foot developed
   into a median fin. Some of the species are naked; others, as
   {Carinaria} and {Atlanta}, have thin glassy shells.
   [1913 Webster]