a nonplane curve whose tangents are all equally inclined to a given plane. the common helix is the curve formed by the thread of the ordinary screw. it is distinguished from the spiral, all the convolutions of which are in the plane.-a caulicule or little volute under the abacus of the corinthian capital.-the incurved margin or rim of the external ear. see illust. of ear.-a genus of land snails, including a large number of species.