(Διοκλῆς), a geometer of unknown date, who wrote περὶ πύριων, according to Eutocius who has cited from that book (Comm. in Sph. et Cycl. Archim. lib. ii. prop. v.) his method of dividing a sphere by a plane in a given ratio. But he is better known by another extract which Eutocius (Op. Cit. lib. ii. prop. ii.) has preserved, giving his mode of solving the problem of two mean proportionals by aid of a curve, which has since been called the cissoid, and is too well known to geometers to need description.