The Collaborative International Dictionary of English v.0.48:

Evidential \Ev`i*den"tial\, a.
   Relating to, or affording, evidence; indicative; especially,
   relating to the evidences of Christianity. --Bp. Fleetwood.
   "Evidential tracks." --Earle.. -- Ev`i*den"tial*ly, adv.
   [1913 Webster]