king of the Veientes, to whom Fidenae revolted in B. C. 438, and at whose instigation the inhabitants of Fidenae slew the four Roman ambassadors, who had been sent to Fidenae to inquire into the reasons of their recent conduct. The names of these ambassadors, were C. Fulcinius, Cloelius, or Cluilius Tullus, Sp. Aritius, and L. Roscius; and statues of all four were placed on the Rostra at Rome, where they continued till a late time (Liv. 4.17; Cic. Phil. 9.2; Plin. Nat. 34.6. s. 11). In the war which followed, Tolumnius was slain in single combat by Cornelius Cossus, who dedicated his spoils in the temple of Jupiter Feretrius, the second of the three instances in which the spolia opima were won. (Liv. 4.18, 19,) [COSSUS, p. 865b.]