amphineura

from The Century Dictionary.

• A class or phylum of Vermes constituted by the genera Neomenia and Chætoderma, together with the Chitonidæ, the latter being removed from the Mollusca and associated with the genera named on account of the similarity in the nervous system.
• A class or order of marine Mollusca.

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

• noun plural (Zoöl.) A division of Mollusca remarkable for the bilateral symmetry of the organs and the arrangement of the nerves.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a class of Gastropoda