Lituus
Lituus , noun
[Latin]
1.
(a) (Rom. Antig.) A curved staff used by the augurs in quartering the heavens.
(b)
(Rom. Antig.) An instrument of martial music; a kind of trumpet of a somewhat curved form and shrill note.
2.
(Mathematics) A spiral whose polar equation is r2θ = a; that is, a curve the square of whose radius vector varies inversely as the angle which the radius vector makes with a given line.