The Collaborative International Dictionary of English v.0.48:

Concameration \Con*cam`er*a"tion\ (-[=a]"sh[u^]n), n. [L.
   concameratio.]
   1. An arch or vault.
      [1913 Webster]

   2. A chamber of a multilocular shell. --Glanvill.
      [1913 Webster]