A rather small family, resembling Scrophulariaceas, widely distributed; parasitic herbs, without green foliage, with alternate scales instead of leaves; flowers perfect, irregular; calyx five-cleft, or split on one or both sides; corolla two-lipped; stamens four, in pairs, with slender filaments, on the corolla-tube (sometimes also the rudiment of a fifth stamen); ovary superior, style slender, stigma disk-like, with two or four lobes; fruit a capsule.

There are several kinds of Thalesia.