OPHIDIA. 457 



is the best. This eminent naturalist divides the Snake into 

 the two sub-orders of the Viperina and Colubrina, the former 

 having only two perforated poison - fangs on the superior 

 maxillae, whilst these bones in the latter carry solid teeth, 

 either with or without additional canaliculated fangs. 



The sub-order Viperina comprises the common Vipers 

 (ViperidcR\ and the Rattlesnakes (Crotalid(B\ the former being 

 mostly confined to the Old World, whilst the latter are wholly 

 American. The common Viper (Pelias berus], occurs abun- 

 dantly in England and Scotland, and is capable of inflicting 

 a severe and even dangerous bite, though it is doubtful if 

 fatal effects ever follow except in the case of children or sub- 



Fig. 197. The Naja Haje, a venomous Colubrine Snake. 



jects previously debilitated. The Rattlesnakes are exclusively 

 natives of America, and they are highly poisonous. The ex- 

 tremity of the tail in the true Rattlesnake (Crotalus horridus] 

 is furnished with a series of horny epidermic cells of an undu- 

 lated pyramidal shape, articulated one within the other, consti- 

 tuting 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. According to 

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

 the Cicada, and thus to attract bird^ which prey upon this 

 insect. The head of the Viperine Snakes (figs. 196, 198) 



