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 berui). 



this group; the Puff- Adder (Bitis 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). 



23I44T The Cheloniansj or Tortoises and Turtles, are distinguished from 

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



