(anc. geog.), the crux geographorum, such being the difficulty of ascertaining its position. It would be endless to recite the several opinions concerning it, with the several reasons advanced in support of them. Three ports are mentioned by Cæsar; two without any particular name, viz. the Higher and the Lower, with respect to the Portus Itius. Calais, Boulogne, St Omer, and Whitstable, have each in their turn had their several advocates. Cæsar gives two distinctive characters or marks which seem to agree equally to Boulogne, and Whitstable, namely, the shortness of the passage, and the situation between two other ports; therefore nothing can with certainty be determined about the situation of the Portus Itius.