122 



VENOMS 



spots, longer than broad, and a series of transverse dark bars on 

 each side ; belly yellowish, spotted with blackish-brown. 



Total length, 200 millimetres ; tail 22. 



Habitat : Vera Cruz, Mexico. 



(d) Crotalus (Battle- Snakes). 



These snakes differ from all others in that the end of the tail 

 bears a series of large conical scales, forming rattles, each fitting 

 into the next and movable in such a manner that when the reptile 

 causes them to move they produce a strident sound (fig. 72) . 



The length of 

 these animals often 

 exceeds 2,000 mil- 

 limetres. The head 

 is flat, very large 

 and expanded pos- 

 teriorly, and ter- 

 minated in front by 

 a short, truncate 

 snout ; it is covered 

 above with scales or 

 small shields. 



Rattle - Snakes 

 are armed with enor- 

 mous fangs enclos- 

 ing a complete canal, 

 which extends 

 throughout almost 

 their entire length. 

 The poison - glands 

 are of the size of a large almond. 



The number of segments in the rattle is variable, but rarely 

 exceeds 18 or 20. At the time of the shedding of the skin these 



/ 



h 



Pig. 72. — A, Horny appendage (rattle) of Crotalus 

 Iwrridus (three-quarters natural size. After Garman). 

 B, longitudinal section of the same. C, separated 

 segments of the appendage : «., terminal point ; h, 

 basal segment (after Czermak). 



