Liberia <«- 



throat under the lower jaw have strong ridges or keels pro- 

 jecting somewhat at their points from the surface of the body. 

 These rough scales on the throat are said to aid the snake in 

 its progression up the trunks and branches of trees. The eyes 

 are proportionately rather larger than in the true vipers. 



The Caiisus viper already referred to has a habit (which 

 may be observed when it is kept in captivity) of dribbling: 

 its venom from the points of the long fangs when it is angry 

 and excited. This pecuHarity has been much noticed by 

 Europeans and natives in South and South-west Africa, 

 where this little viper shares with the much larger cobra the 

 nickname of " spitting snake." The Cobras, of course, are 

 not connected with the vipers at all. They are simply a 

 group of colubrine snakes that have independently acquired 

 the feature of a poison gland and a perforated fang. They 

 may be told at a glance from the average viper by the narrow 

 jaws. The skin on the sides of the neck in the common 

 African form of Naja haje is dilatable into a hood, but this 

 feature is not so striking as in the common Indian cobra or 

 the hooded snake {Sepedon) of South Africa. The West 

 African torms of cobra are regarded as separate species — TV. 

 nigricollis, from the black markings on the back of the neck 

 spreading into a general black tinge, and A^. melanoleuca, in 

 which the o-eneral colourins; is in bolder contrast of black 

 and white. These cobras are fairly common in Liberia, where 

 they often attain a length of four to eight feet. Naja nigricoUis 

 is not infrequently seen in native villages, which it visits on 

 account of the rats and other vermin that form its food. 

 The snakes frequent the thatch more especially, and do not 

 generally interfere with human beings unless first attacked. 

 Even then, instead of striking with their fangs they seem to 

 prefer to eject the venom by compression of the muscles of 



8lQ 



