THE VIPERS 2593 



THE VIPERS 

 Family 



Omitting mention of the small and unimportant family of harmless snakes 

 Vnown as blunt heads (Amblycephalidce] , represented by two Oriental and two trop- 

 ical American genera, we pass to the viper family, which includes the whole of the 

 remaining members of the suborder. The distinction between a colubrine and 

 viperine snake is that in the latter the maxillae or hinder upper jawbones are capa- 

 ble of being erected in a vertical plane at right angles to the transverse bones, while 

 in form they are short and thick, and they always carry a single pair of large tubu- 

 lar fangs. All vipers are poisonous, and, so far as known, produce living young; 

 while they are more or less nocturnal and terrestrial in their habits, although a few 

 ascend trees. The thick body, the flat and often triangular head, the short and 

 stumpy tail, the reduction of the maxillary teeth to a single pair of fangs, and the 

 vertical pupil of the eye, are all features distinguishing vipers as a whole from the 

 poisonous colubrines; but, as already mentioned, it is frequently necessary to exam- 

 ine ' the structure of the skull itself before any particular snake can be assigned to 

 its proper serial position. That the vipers form a highly specialized group is self- 

 evident; and Mr. Boulenger believes them to be descended from the hind-fanged 

 colubrines. The family is divided into two groups, namely, the typical vipers of 

 the Old World, which attain their maximum development in Africa, and the Amer- 

 ican and Asiatic pit vipers. 



Our first representatives of the Old-World vipers ( Viperince) are the 

 True Vipers , . , r ... 



true vipers, which torm 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 distinguished 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 Brit- 

 Common Viper ... . 



ish 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 color 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 color 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 con- 

 fluent 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 color, and are fre- 

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