Total length, 2,000 millimetres; tail 430. _Habitat_: West Africa, south of the Congo; Central Africa, East Africa, Transvaal, Natal. (4) _D. antinorii._--Scales in 21-23 rows; 248 ventrals; 117 subcaudals. Colour olive on the back, yellowish on the belly. Total length, 2,690 millimetres; tail 545. _Habitat_: Abyssinia. II.--VIPERIDÆ. The African _Viperidæ_ all belong to the Subfamily _Viperinæ_, of which the following are the seven principal genera:-- (a) _Causus_. (b) _Vipera_. (c) _Bitis._ (d) _Cerastes._ (e) _Echis._ (f) _Atheris._ (g) _Atractaspis._ (a) =Causus.= (Fig. 35.) Head distinct from the neck, covered with symmetrical shields; nostril between two nasal shields, and the internasal; eyes moderate, with round pupils, separated from the lips by subocular shields. Body cylindrical; scales smooth or keeled, oblique on the sides, in 15-22 rows; ventral scales rounded. Tail short; subcaudals in 2 rows or single. Four species:-- (1) _C. rhombeatus._--Snout obtuse, moderately prominent. Scales in 17-21 rows; 120-155 ventrals; 15-29 subcaudals. Colour olive or pale brown, usually with a series of V-shaped brown spots bordered with white, and a large spot in the form of a circumflex accent at the back of the head; lips bordered with black; belly yellowish or grey. Total length, 700 millimetres; tail 75. _Habitat_: Tropical and South Africa, from the Gambia to the Cape. (2) _C. resimus._--Snout prominent, more or less turned up; scales in 19-22 rows; 134-152 ventrals; 17-25 subcaudals. Colour greyish-olive on the back; uniform white on the belly. Total length, 470 millimetres; tail 40. _Habitat_: Central and East Africa, Angola. (3) _C. defilipii._--Snout prominent, more or less turned up. Scales in 17 rows; 113-125 ventrals; 10-18 subcaudals. Colour grey or pale brown above, with a series of large rhomboidal or V-shaped blackish-brown spots; a large A-shaped dark brown mark on the occiput; an oblique dark streak behind the eye; supralabial shields edged with black; belly yellowish. Total length, 400 millimetres; tail 22. _Habitat_: Central and East Africa, Transvaal. [Illustration: FIG. 35.--SKULL OF _Causus rhombeatus._ (After G. A. Boulenger, _op. cit_.)] (4) _C. lichtensteinii._--Snout obtuse; scales in 15 rows; 142-144 ventrals; subcaudals 15-21, single. Colour greyish, with rather indistinct darker chevron-shaped cross-bands. Total length, 413 millimetres; tail 35. _Habitat_: West Africa (Gold Coast), Congo. (b) =Vipera.= (For the characters of this genus, see p. 23,--Europe.)