24 GUIDE TO REPTILES AND AMPHIBIANS. 



fig. 16), the Indian Russell's Viper (V. russelli, 320), and the African 

 Puff -Adder (Bitis arietans, 315), Gaboon Puff -Adder or Viper 

 (B. gabonkas, 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 (Crotalinm) 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 (Ancistrodon 

 piscivorus, 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 Homed Puff-Adder (Bitis nasicornis) , a venomous Serpent. (No. 3I6-) 



m, 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 ; 

 pm, premaxillary ; q, quadrate bone. 



From a specimen in the Museum. 



lanceolatus, 326 a), the Indian Green Viper (L. gramineus), the 

 green Wagler's Viper (Lachesis wagleri, 327) of Malaysia, which 

 lives in trees, and the great black and orange Curucucu (L. mutus, 

 328) of Surinam. 



The American Rattle-Snakes (Crotalus and Sistrurus), 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 



