230 SNAKES. 



Our first representatives of the Old World vipers ( Viperince) 

 are the true vipers, which form a genus with some twenty species, 

 ranging over Africa (exclusive of Madagascar), Europe, and a large portion of Asia, 

 one of them reaching India. In common with the other members of the subfamily, 

 they have no pit in the loreal shield of the head ; while they are specially dis- 

 tinguished by the upper surface of the head being covered either with scales or 

 small shields, and by the keeled scales of the body running in straight longitudinal 

 rows, which vary in number from twenty-one to thirty-eight ; and likewise by the 

 double row of shields beneath the tail. 



The common viper (Vipera verus), which is happily the only 

 ° British poisonous snake, is one of the smallest representatives of the 

 genus, and is distinguished by the mixture of scales and shields on the head (three 

 of the latter being larger than the rest), and the general presence of only a single 

 row of scales between the eye and the upper labial shields beneath. In colour and 

 markings the common viper is extremely variable ; but as a rule a dark zigzag 

 stripe runs down the whole length of the middle of the back. With regard to 

 coloration, in some specimens the ground-colour is nearly olive, in others a deep 

 rich brown, and in others a dirty brownish yellow ; while a mark between the 

 eyes, a spot on each side of the hinder part of the head, the above-mentioned zigzag 

 line formed of confluent quadrangular spots on the back, and a row of small 

 irregular triangular spots on each side of the body, are of a darker hue than the 

 ground-colour, and are frequently nearly black. In some examples the under- 

 pays are lead-colour, with lighter or darker spots, while in others they are almost 

 wholly black. Bell records a specimen in which the ground-colour was nearly 

 white and the markings black ; and in one variety the ground-colour is brick-red, 

 with ferruginous markings ; while in a second the under-parts acquire a more or 

 less marked blue tinge ; and in a third the whole skin, with the exception of that 

 beneath the jaw and throat is black, the usual markings being visible in certain 

 lights. The average length of the common viper is about 10 inches. Its geo- 

 graphical distribution is greater than that of any other European snake, extending 

 from Portugal eastwards to the Island of Saghalien, while northwards it reaches 

 to the Arctic Circle, and southwards to Central Spain. 



In South-Western Europe the common viper is replaced or 

 Southern Viper. . ' , * x 



accompanied by a closely-allied form which may be called the 



southern viper (V. aspis), regarded by some writers as a distinct species, and by 



others as a mere variety. As it was doubtless to this snake that the Latin term 



Vivipara was applied, German writers restrict the name viper to the southern 



form, and use the term Krewzotter for the common viper. In the latter 



the front of the upper surface of the head is covered with three distinct small 



shields, but in the southern form it is clothed only with smooth or slightly ridged 



scales, among which seldom more than a single polygonal roundish one can be 



regarded as representing a frontal shield ; moreover, instead of the single row of 



small scales generally separating the eye of the common viper from the upper 



labial shields, the southern form always has two such rows. There is likewise a 



difference in the shape of the muzzle in the two forms. The southern viper may 



be considered characteristic of the Mediterranean countries, occurring in North 



