\Pte*rop"o*da\, n. pl. [NL.] (Zo["o]l.)
A class of Mollusca in which the anterior lobes of the foot
are developed in the form of broad, thin, winglike organs,
with which they swim at near the surface of the sea.
Note: The Pteropoda are divided into two orders:
      {Gymnosomata}, which have the body entirely naked and
      the head distinct from the wings; and {Thecosomata},
      which have a delicate transparent shell of various
      forms, and the head not distinct from the wings.