The Collaborative International Dictionary of English v.0.48:

Rhachiglossa \Rhach`i*glos"sa\, n. pl. [NL. See Rhachis, and
   Glossa.] (Zool.)
   A division of marine gastropods having a retractile proboscis
   and three longitudinal rows of teeth on the radula. It
   includes many of the large ornamental shells, as the
   miters, murices, olives, purpuras, volutes, and
   whelks. See Illust. in the Appendix.
   [1913 Webster]