The Collaborative International Dictionary of English v.0.48:

Tribual \Trib"u*al\, Tribular \Trib"u*lar\, a.
   Of or relating to a tribe; tribal; as, a tribual
   characteristic; tribular worship. [R.]
   [1913 Webster]

         The tribual lispings of the Ephraimites. --Fuller.
   [1913 Webster]