The Collaborative International Dictionary of English v.0.48:

Perennibranchiate \Per*en`ni*bran"chi*ate\, a. [See Perennial,
   and Branchiate.]
   1. (Anat.) Having branch[ae], or gills, through life; -- said
      especially of certain Amphibia, like the menobranchus.
      Opposed to caducibranchiate.
      [1913 Webster]

   2. (Zool.) Belonging to the Perennibranchiata.
      [1913 Webster]