TRICESIMUM, AD, in Gallia. D'Anville observes that the ancient Itins. contain many positions with similar names, which names of places are derived from the distances which they indicate from the principal towns; for the distances within the dependent territory were measured from the principal towns. This Tricesimum is measured from Narbo ( Narbonne), as the Jerusalem Itin. shows, on the road to Toulouse, through Carcassonne. Trebeson the canal of Languedoc may represent the name; and Tricesimum may be near that place.
[G.L]