THE PBINCIPAL SPECIES OF POISONOUS SNAKES 49 



In moving over the ground a peculiar sound is produced by the 

 friction of its scales. It is capable of springing with great agility 

 a fairly long distance on to its prey. When it believes itself in 

 danger it coils up, doubling its body twice in the shape of a 

 crescent, in the middle of which it places its head, ready to 

 strike. Its venom is very rapid in taking effect. 



2.— OEOTALIN^. 



(e) Ancistrodon. 



The snakes belonging to this genus of Crotalinm are found in 

 Central and Eastern Asia, but three important species occur in the 

 New World, in the United States and Central America. The head 

 is covered with nine large symmetrical shields, but the internasals 

 and prefrontals are sometimes broken up into scales. The body 

 is cylindrical ; the tail rather short ; the subcaudal scales are 

 arranged in one or two rows. 



A. xicutus. — The snout of this snake is prolonged into an append- 

 age directed forwards. The head-shields are finely granulate. Body 

 scales arranged in 21 rows ; 162—166 ventrals ; 58 — 60.subcaudals. 



Coloration brown on the back, with blackish-brown X-shaped 

 spots ; head dark brown, yellow on the cheeks, with a black band 

 running from the eye to the angle of the jaw ; belly yellowish, 

 spotted with brown, with a series of large black transverse blotches. 



Total length, 1,500 millimetres ; tail 200. 



Habitat : Upper Yang-tse, China. 



A. halys. — Snout prolonged into an upturned appendage, blunt 

 at the tip ; 7—8 supralabial scales, the third of which forms part 

 of the margin of the eye; body scales in 23 rows ; 149 — 174 

 ventrals ; 31—44 subcaudals. 



Coloration yellowish, grey, red, or pale brown above, with darker 

 spots or cross-bars. A black spot on the snout ; two black spots 

 4 



