THE PRINCIPAL SPECIES OF POISONOUS SNAKES 79 
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; postocu- 
lar in contact with a 
large temporal; one 
preocular; frontal 
as long as or slightly 
shorter than the 
parietals. Scales on 
Fic. 42.—SKkuLL oF Atractaspis aterrima (African 
the body in 19—921 Viperine). (After G. A. Boulenger, op. cit.) 
rows ; 209—230 ven- 
trals ; 19—23 sub-caudals. 
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. 
