24 REPTILE GALLERY. 



most of them on the ground. They are viviparous. The true 

 Vipers are chiefly African, a few species only occurring in Europe 

 and Asia. The common British Viper is one of the smallest of 



Fig. 19. 



Common Viper {Vipera berus). 



this group; the Puff- Adder {Litis arietans), the most dangerous 

 Snake of South Africa. 



The Pit-Vipers and Rattlesnakes are found only in Asia and 

 America, most abundant and reaching a larger size in the latter 

 part of the world. The true Rattlesnakes {Crotalus) are distin- 

 guished by the " rattle^' at the end of the tail, formed by several 

 horny rings, which the animal shakes when irritated, producing a 

 peculiar sound. It is stated that the length of the " rattle ■'■' 

 indicates the age of the individual ; and it is a fact that rattles of 

 such a length and so many joints (twenty-one), as are exhibited in 

 Case 22, are now of extremely rare occurrence, as these dangerous 

 creatures, with the advance of cultivation, have now but rarely the 

 chance of surviving to a very old age. 



Order V. CHELONIA (Tortoises and Turtles). 



The Chelonians^ or Tortoises and Turtles, are distinguished from 

 all other Reptiles by the more or less ossified case or " shell 



