The Collaborative International Dictionary of English v.0.48:

lampshell \lampshell\, lamp shell \lamp shell\n.
   A mollusklike marine animal with bivalve shell having a pair
   of arms bearing tentacles for capturing food, found
   worldwide.

   Syn: brachiopod.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

lampshell
    n 1: marine animal with bivalve shell having a pair of arms
         bearing tentacles for capturing food; found worldwide [syn:
         brachiopod, lamp shell, lampshell]