176 



REPTILES AND BATRACHIANS 



remarkable in being very elongate, and is situated at the 

 side of the neck between the skin and the body muscles ; 

 it is produced along each side, terminating in front of the 

 heart, which is situated about the anterior third of the body. 

 The commonest and best known species is the Night 

 Adder, C. rhovibeatus, which has a wide distribution in 

 Tropical as well as South Africa : it grows to a length of 

 nearly three feet. It is olive or pale brown above, with a 

 dorsal series of large rhomboidal dark brown spots ; a 

 large dark, y\^-shaped marking is situated on the back of 



Labial 



Poison QIand 



Fig. 9. — Head and neck of Causus resimus. 



{After JVerner.) 



the head. The snake, which, in spite of its popular name, 

 is by no means essentially nocturnal, feeds principally on 

 frogs, of which it devours large quantities, a large specimen, 

 living at the time of writing in the Zoological Gardens, 

 consuming on an average about twenty frogs a month. 

 When angry the Night Adder has the peculiar habit of 

 dribbling its venom from the point of its fangs. Unlike 

 the majority of vipers, the members of the genus Causus 

 do not produce active young, but lay eggs, which are 

 deposited under decomposing vegetable matter. 



The snakes of the genus BitiSy restricted to Africa, have 



