VIPERINE GROUP. 



235 



its loud hissing is calculated to warn those who approach it, and it does not 

 appear to cause many human deaths, although it may be that its misdeeds are 

 sometimes ascribed to the cobra. This viper is said to frequently kill cattle while 

 grazing, by biting them about the nose or mouth. In proof of its sluggish nature, 

 there is a well-authenticated tale of a young person having picked one up, and, 

 mistaking it for an innocent snake, carried it home ; its true character being only 

 discovered when it bit a dog." 



In Africa the place of Russell's viper is taken by the dreaded 

 puff-adder ( V. arietans), which occasionally attains a length of 6 feet. 

 It is the only member of the genus in which the unusually small nostrils open 



Puff-Adder. 



THE puff-adder (£ nat. size). 



upwards near the extremity of the muzzle ; and it is further distinguished by 

 having a supranasal shield, covered, like the region of the brow, with upright 

 horny scales or spines. In appearance most hideous and repulsive, this snake has 

 the large and flattened head triangular in shape, very broad and blunt at the 

 muzzle, and sharply defined from the body, the latter being thick and almost 

 triangular in section. Both head and body are covered with keeled overlapping 

 scales, differing from one another only in size, and arranged on the body in from 

 thirty-one to thirty-three longitudinal rows, and forming three or four series 

 between the eyes and the upper labials. The coloration and marking vary to a 

 certain extent individually ; but there is a great change in the brightness of the 

 tints immediately after the changing of the skin. The puff-adder is spread over 



