[f. Gr. κογχο- (see CONCHOLOGY) + -SPIRAL.] A kind of spiral curve exemplified in shells.
1864. Webster cites Agassiz.
1876. A. MacAlister, Anim. Morph., 283. Coiled shells are spirals of a peculiar modulus, resembling (and in Ammonites identical with) the true logarithmic spiral, usually differing in having a definite point of starting, and forming another geometrical species, the concho-spiral.
