386 



NATURAL HISTORY. 



The other snakes to be mentioned all belong to the New World, and 

 from their numbers and their importance they demand more attention than 

 those that ha ve gone before. 



Most celebrated of all our snakes are the rattlesnakes, of which the 

 United States contains seventeen distinct species. The principal genus is 

 Crotalus, and this derives its name from the Latin. In the language of 

 ancient Rome the Castanet worn by dancing-girls was called crotalum, 

 and so when Linne was hunting for a name for our serpent, what was 

 more natural than that he should pitch upon this word ? For the rattle- 





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Fig. 341.— Horned viper ( Vipera cerast.is). 



snake is provided with a Castanet of a most peculiar pattern, and one which 

 is nowhere paralleled in the whole animal kingdom. This rattle termi- 

 nates the tail, and is composed of a number of dry hollow rings loosely 

 hinged together and ending in a rounded button. Each time the skin is 

 cast, another ring is added to the rattle, and in one case as many as forty- 

 l'onr of these rings have been recorded in the tail of one of these reptiles. 

 Twelve or fourteen is, however, the usual number in our more common 

 eastern species. It is usually supposed that the number of rings in the 

 rattle may be taken as an index of age. This belief is an old one, and 



