24 



GUIDE TO REPTILES AND AMPHIBIANS. 



fig. IG), the Indian Russell's Viper (F. russeUi, 320), and the African 

 Puff -Adder {Bitis arietans, 315), Graboon Puff- Adder or Viper 

 {B. (lahonkas, 317), and Horned Puff-Adder {B. nasicornis, 316)- 

 All these African Vipers are brilliantly coloured, but the Horned 

 Viper {Cerastes cornutus) of North Africa is coloured to correspond 

 with the desert-sand. 



The Pit- Vipers {Crotalince) take their name from the presence of 

 a pit, which probably subserves some sense-function, between the eye 

 and nose. The typical American forms {Crotalus) are called Rattle- 

 ' snakes from the presence of a number of loose horny rings at the 

 end of the tail. Other kinds are the Water- Viper {Ancisfrodon 

 piscii'ori/s, 330) and the Copper-head (A. contortrix, 329) of North 

 America, the South American and West Indian Fer-de-lance {Lachesis 



Fig. 22. 



Skull of Horned Puff-Adder (Bitis nasicornis) , a venomous Serpent. (No. 3I6-) 



w, maxillary, with poison-fang ; a bristle is inserted in the openings of the 

 channel at the base and point of the tooth ; d, undeveloped poison-fangs ; 

 2nn, premaxillary ; q, quadrate bone. 



From a specimen in the Museum. 



lanceolatus, 328 a), the Indian Green Viper {L. (iramineus), the 

 green Wagler's Viper {Lachesis J^vagleri, 327) of Malaysia, which 

 lives in trees, and the great black and orange Curucucu {L. mufus, 

 328) of Surinam. 



The American Rattle-Snakes {Crotalus and Sistnirus), as already 

 mentioned, have at the end of the tail a rattle composed of a 

 number of horny rings or bell-like structures which fit into one 

 another. The oldest, or terminal, bell is really the horny sheath of 

 the tail-tip ; and with each casting of the skin the youngest bell 

 becomes loose, but is held in place by the new covering. An ever- 

 increasing number of loosely-attached bells is thus produced ; but 



