The Collaborative International Dictionary of English v.0.48:

menobranch \men"o*branch\, Menobranchus \Men`o*bran"chus\, n.
   [NL. menobranchus, fr. Gr. ? to remain + ? a gill.] (Zool.)
   A large aquatic American salamander of the genus Necturus,
   having permanent external gills.
   [1913 Webster] Menologium