This genus is characterised by enormous poison-fangs, a few teeth on the palatines, and none on the pterygoids. The mandible, which is edentulous in front, has only two or three small teeth in the middle of the dentary bone. Head small, not distinct from the neck, covered with large symmetrical shields; nostril between two nasal shields; eyes minute, with round pupils; postfrontal bone absent. Body cylindrical; scales smooth, in 17-37 rows; ventrals rounded. Tail short; subcaudals in 1 or 2 rows. (1) _A. hildebrandtii._--Six supralabials; no præocular shields; frontal shorter than the parietals; scales on the body in 17 rows; ventrals 167-174. Colour uniform dark brown. Total length, 450 millimetres; tail 53. _Habitat_: East Africa. (2) _A. congica._--Five supralabials, of which the fourth is the larger; postocular in contact with a large temporal; one præocular; frontal as long as or slightly shorter than the parietals. Scales on the body in 19-21 rows; 209-230 ventrals; 19-23 subcaudals. [Illustration: FIG. 42.--SKULL OF _Atractaspis aterrima_ (African Viperine). (After G. A. Boulenger, _op. cit._)] Colour uniform dark brown or black. Total length, 450 millimetres; tail 35. _Habitat_: Congo, Angola. (3) _A. irregularis._--Characters as before, but scales on the body in 25-27 rows; 220-257 ventrals, subcaudals 22-28 pairs. Colour uniform black or dark brown. Total length, 560 millimetres; tail 35. _Habitat_: West Africa, from the Gold Coast to the Congo; Central Africa. (4) _A. corpulenta._--Postocular shield in contact with a large temporal; second lower labial very large, fused with the chin-shields. Scales on the body in 23-27 rows; 178-193 ventrals; 23-27 subcaudals. Colour uniform blackish-brown; tail sometimes white. Total length, 345 millimetres; tail 33. HABITAT: West Africa, from Liberia to the Gaboon. (5) _A. rostrata._--Snout very prominent, cuneiform. Third lower labial very large; first lower labial in contact with its fellow, behind the symphysial. Scales on the body in 19-23 rows; ventrals 227-248. Colour uniform dark brown, or blackish. Total length, 600 millimetres; tail 37. _Habitat_: East and Central Africa. (6) _A. bibronii._--Characters as before. Snout prominent, subcuneiform. Ventral scales, 221-260. Colour dark purplish-brown above, dull yellow or pale brown on the belly. Total length, 600 millimetres; tail 25. _Habitat_: Eastern districts of Cape Colony, Natal, Namaqualand, Angola. (7) _A. aterrima._--Characters as before. Snout rounded; 251-300 ventral scales. Colour uniform dark brown or black. Total length, 650 millimetres; tail 30. _Habitat_: West and Central Africa. (8) _A. dahomeyensis._--Characters as before. Symphysial shield in contact with the chin-shields. Scales on the body in 31 rows; 240 ventrals; 24 subcaudals. Colour black above, brown on the belly. Total length, 490 millimetres; tail 32. _Habitat_: Dahomey.