542 MANUAL OF ZOOLOGY. 



mity of the tail in the true Rattlesnake ( Crotalus horridus, fig, 

 295) is furnished with a series of horny epidermic cells of an 

 undulated pyramidal shape, articulated one within the other, 



Fig. 299. The Naja Haje, a venomous Colubrine Snake. 



constituting an appendage which is known as the "rattle." 

 Before striking its prey, the Rattlesnake throws itself into a 

 coil, and shakes its rattle, as it does also when alarmed. Ac- 

 cording to Professor Shaler, the use of the rattle is to imitate 

 the note of the Cicada, and thus to attract birds which pre; 

 upon this insect ; but its function is more probably sexual. 

 The Indian snakes belonging to the genus Trimeresurus, and 

 some other less important forms, are also placed amongst the 

 Crotalidcz. The head of the Viperine Snakes (figs. 296, 300) 

 is broad, somewhat triangular in shape, broadest in its middle, 

 and showing a very distinct line of demarcation between the 

 head and neck. The head, also, is usually covered with small 

 scales, rarely interspersed with larger plates or " scuta " (fig. 

 300). Other well-known members of this group are the Death- 

 adder (Acanthophis tortor) of Australia, the Horned Viper 

 (Cerastes) of Africa, and the Puff-adder (Clotho arietans) of the 

 Cape of Good Hope. , 



(2.) The Elapina are poisonous snakes, in which the poison- 

 fangs are permanently fixed and erect, and have smaller solid 



