VIPERINAE 641 



In the daytime it is invisible, being buried in the sand with 

 only the eyes, nostrils, and the " horns " appearing above the 

 surface. 



Vipera. — The head is distinct from the neck, and is covered 

 with small scales and a few larger shields. The eye is separated 

 from the labials by scales ; the nasals are in contact with the 

 rostral shield or separated by one naso-rostral shield. The scales 

 on the body are strongly keeled ; they are in two rows on the 

 short tail. This genus with about ten species ranges over 

 Em'ope, Asia, and the greater part of Africa. 



V. lerus, the Common European Viper (see Fig. 165, p. 620). 

 The snout is not turned up at the end ; between the small head- 



FlG. 173.— Cerastes cornutus, the "Horned Viper" (right), and Vipera ammodytes, the 

 "European Nose-horned Viper " (left), x 1. 



scales there is generally a pair of well -developed parietal and 

 frontal shields. The scales of the trunk form twenty-one rows. 

 The coloration is very variable, there being grey, brown, red, or 

 black specimens in the same country, and the much-spoken-of 

 black zigzag line along the back is so often indistinct that it is a 

 character not to be relied upon. Usually the grey, yellowish, 

 olive, brown or red ground-colour is set off by a dark zigzag band 

 along the spine, and by a series of lateral spots ; an oblique or 

 St. Andrew's cross or two diverging bold streaks of dark brown 

 or black are usually present on the back of the head, and there is 

 a dark streak behind the eye. The under parts are grey, brown, 

 or black, uniform or speckled ; the end of the tail is usually 

 yellow or red. According to Boulenger, who is making a special 

 study of the individual variations of Vipers (concerning colour, 

 scaling, number of vertebrae, etc.), some specimens are entirely 



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