The Collaborative International Dictionary of English v.0.48:

Invertebrate \In*ver"te*brate\, a. (Zool.)
   Destitute of a backbone; having no vertebr[ae]; of or
   pertaining to the Invertebrata. -- n. One of the
   Invertebrata.
   [1913 Webster]

   Age of invertebrates. See Age, and Silurian.
      [1913 Webster]