THE PRINCIPAL SPECIES OF POISONOUS SNAKES 67 



(a) Causus. 



(b) Vipera. 



(c) Bitis. 



(d) Cerastes. 



(e) Echis. 



(f) Athens. 



(g) Atractaspis. 



(a) Causus. 



(Pig. 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. rJiombeatus. — Snout obtuse, moderately prominent. 

 Scales in 17 — 21 rows ; 120 — 15.5 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 miUimetres ; 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. defiUpii. — Snout prominent, more or less turned up. 

 Scales in 17 rows ; 113 — 125 ventrals ; 10 — 18 subcaudals. 



