The Collaborative International Dictionary of English v.0.48:

Calipash \Cal`i*pash"\, n. [F. carapace, Sp. carapacho. Cf
   Calarash, Carapace.]
   A part of a turtle which is next to the upper shell. It
   contains a fatty and gelatinous substance of a dull greenish
   tinge, much esteemed as a delicacy in preparations of turtle.
   [1913 Webster]