This genus includes several species of snakes of somewhat small size, rarely exceeding 700 millimetres in length, with an elongate, cylindrical body; the head is scarcely distinct from the neck, the pupil round, and the tail short, while the nostril is situate between two nasal shields. The temporal shields are arranged in a single row. The poison-glands sometimes extend into the abdominal cavity. Scales in 13 or 15 rows; 190-260 ventrals, 12-44 subcaudals in 2 rows.
Four species belonging to this genus are known:—
(1) H. calligaster.—2 + 3 temporal scales, 6 supralabials.
Colour purple, with black transverse bands separated by narrow white bars; belly and end of tail red; snout yellow, with a black band on the upper lip below the eyes.
Total length, 520 millimetres; tail 30.
Habitat: Philippine Islands.
(2) H. collaris.—No anterior temporal scales.
Colour black on the back, with black and red bands on the belly; a yellow collar on the occiput.
Total length, 430 millimetres; tail 15.
Habitat: Philippine Islands.