\Brach`i*op"o*da\, n. [NL., from Gr. ? arm + -poda.]
(Zo["o]l.)
A class of Molluscoidea having a symmetrical bivalve shell,
often attached by a fleshy peduncle.
Note: Within the shell is a pair of ``arms,'' often long and
      spirally coiled, bearing rows of ciliated tentacles by
      which a current of water is made to flow into the
      mantle cavity, bringing the microscopic food to the
      mouth between the bases of the arms. The shell is both
      opened and closed by special muscles. They form two
      orders; Lyopoma, in which the shell is thin, and
      without a distinct hinge, as in Lingula; and
      Arthropoma, in which the firm calcareous shell has a
      regular hinge, as in Rhynchonella. See {Arthropomata}.