THE PRINCIPAL SPECIES OF POISONOUS SNAKES 67 
(a) Causus. 
(b) Vipera. 
(cvs: 
(d) Cerastes. 
(e) Echas. 
(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. 
