Description from Flora of China
Shrubs, subshrubs, or herbs, with cystoliths. Leaves opposite, petiolate or subsessile; leaf blade margin entire or slightly undulate. Inflorescences axillary or terminal, spikes or racemes, sometimes branched into panicles; bracts and bracteoles shorter than calyx. Calyx deeply 5-lobed; lobes subequal. Corolla white or greenish [or purple]; tube cylindric, elongate, narrow; limb 2-lipped; lower lip 3-lobed, lobes ascending cochlear in bud; upper lip entire or 2-cleft, inside rugulose. Stamens 2, exserted from mouth of corolla; anthers 2-thecous; thecae unequally inserted to superposed, lower theca with or without a basal appendage; staminodes absent. Capsule with a solid stalk, clavate, 4-seeded; retinacula present. Seeds discoid, variously ornamented, lacking trichomes.
Rhinacanthus calcaratus (Wallich) Nees was reported from Yunnan by C. C. Hu (FRPS 70: 268. 2002) based on a misidentification of Pseuderanthemum polyanthum.
About 25 species: tropical and subtropical regions of Africa and Asia; two species (one endemic) in China.
(Authors: Hu Jiaqi (胡嘉琪 Hu Chia-chi), Deng Yunfei (邓云飞); Thomas F. Daniel)