Varix (Pl. varices) is a thickened axial ridge in the shell of some types of Littorinimorpha and Neogastropoda, located at intervals around the whorl, and formed by thickening of the outer lip at a resting stage in the growth of the shell. In most gastropods bearing varixes (e.g. Cassidae, this is essentially a thickening or swelling of the shell at that point.