trachelipoda

from The Century Dictionary.

• noun In Lamarck's classification, the third order of mollusks, containing those univalves whose foot is attached to the neck (whence the name), and whose shell is spiral.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Zoöl.) An extensive artificial group of gastropods comprising all those which have a spiral shell and the foot attached to the base of the neck.