螺旋结构（helix 的复数）

Helix \He"lix\, n.; pl. L. {Helices}, E. {Helixes}. [L. helix,
Gr. ?, ?, fr. ? to turn round; cf. L. volvere, and E. volute,
voluble.]
1. (Geom.) 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.

2. (Arch.) A caulicule or little volute under the abacus of
the Corinthian capital.

3. (Anat.) The incurved margin or rim of the external ear.
See Illust. of {Ear}.

4. (Zo["o]l.) A genus of land snails, including a large
number of species.

Note: The genus originally included nearly all shells, but is
now greatly restricted. See {Snail}, {Pulmonifera}.