Maxillary short, with 6-9 small teeth followed by a large grooved fang situated below the eye. Anterior mandibular teeth longest. Head small, not distinct from neck. Eye small, with round pupil. Nasal entire or divided; no loreal. Body cylindrical; tail moderate or short. Dorsal scales smooth, without pits, arranged in 15 rows. Ventrals rounded; subcaudals single (not divided or paired).
*) Not including the nominate subspecies. T) Type species.