NUMBERS AND DISTRIBUTION. 215 
GENus CAUSUS. 
Two Species in South Africa. 
KEY TOMES SPE CEES: 
Snout obtuse, more or less prominent; ventrals 
120-155. Poison glands considerably elon- 
Causus vhombeatus. 
gated Ne es 3 ee e 
Snout pointed, prominent, more or less turned up 
at the end; ventrals 113-125 .. a .. Causus defillippir. 
Fic. 85.—The venomous Hornsman or Horned Adder (Bitis caudalis) of the sandy 
inland parts of South Africa (two-thirds natural size). 
I. CAUSUS RHOMBEATUS, Night or Demon Adder. Nacht Ader (Adder). 
Synonyms—Sepedon rvhombeatus ; Distichurus macuiatus ; Aspidelaps 
vhombeatus. 
Colour—Olive or pale brown above, rarely uniform, usually with a 
dorsal series of large rhomboidal or V-shaped dark brown spots 
which may be edged with whitish; usually a large dark j-shaped 
marking on the back of the head, the point on the frontal, and 
