Where does one begin and the other end? I ask this because I was looking at some seashells that are called volutes, and I thought that they seemed more to be helixes because they crossed many planes in rising (or falling) spirals. I think of a volute as a spiral along one broad plain, as a volute in a fiddlehead (i.e., violin).

But perhaps volute and helix are pretty much interchangeable as words. I don't know.

Would someone care to comment on these shapes?