Shrub c. 50 cm, much branched, glabrous in all parts except corolla. Stems ridged-angled, rather slender. Leaves with sessile oil globules, oblanceolate, c. 20-35 x 3-7 mm, margins quite entire, apically acuminate, obtuse or acute with a single spiny tip, subsessile; leaves mostly in lower parts of stem; spines present in all leaf axils. Verticillasters 6-10-flowered, all remote. Spines sturdy, c. 10 mm, horizontally spreading or recurred. Flowers sessile. Calyx glabrous, coriaceous, glaucous, 10-nerved, bilabiate; tube 10-12 mm long, glabrous at throat; lower lip ovate, subentire, mucronate or not, about as long as tube in flower, prominently reticulate-veined, much expanded in fruit, whitish and reflexed; upper lip 3-lobed, middle lobe slightly larger than ovate laterals, mucronate, much shorter and smaller than lower lip. Corolla white; tube c. 8 mm, not or scarcely exserted from the calyx tube; upper lip c. 5 mm long, densely villous. Nutlets (immature) glabrous, prominently truncate.