Wiktionary
conchospiral
n. A kind of spiral curve found in certain univalve shells.
Wikipedia
Conchospiral
In mathematics, a conchospiral is a three-dimensional spiral. In cylindrical coordinates, it is described by the parametric equations:
r = μa
θ = t
z = μc.
The projection of a conchospiral on the (r, θ)-plane is a logarithmic spiral.