Perennial, stoloniferous herb. Lvs simple, ± crenately toothed. Fls in dense axillary whorls; bracts resembling lvs. Calyx tubular-campanulate, 10-veined, not gibbous at base; teeth 5, almost equal, subulate. Corolla bilabiate, yellow; upper lip helmet-shaped, laterally compressed; lower lip with 3 almost equal lobes, the middle lobe ± triangular; tube > calyx, dilated in upper part, with ring of hairs inside. Stamens lying below upper lip; anther cells divergent, glabrous. Style gynobasic, its arms subequal. Nutlets trigonous, smooth.