VIPER, a genus of venomous snakes, representative of the family Viperidc. This family includes many important forms—e. g., the common adder (Vipers or Pelias bents); the asp (V. aspis), ex tending as far N. as Sweden; the Afri can horned viper (V. cerastes) and puff adder (Clotho or Echidna arietans) ; the Indian daboia or Russell's viper (Dab oia russellii); and the Indian Echis carinata. The head is relatively broad, somewhat triangular, and generally covered with scales; the eye has a vertical pupil, and there is no pit between it and the nostril; the maxilla bears on each side one func tional fang, usually with several reserve fangs beside it; the poison is virulent. The vipers are widely distributed through Europe and Australia; the majority are African. As far as is known they are viviparous.
The common viper or adder is the only poisonous snake indigenous to Great Britain. It lives especially on dry heaths and waste places, often among stones and brushwood; it is commoner in Scotland than in England, and does not occur in Ireland. It is widely dis tributed throughout Europe. Often con fused with the innocent grass snake (Tropedonotus natrix), it may be distin guished by its markings. It has two diverging marks between and rather be hind the eyes, a spot on each side of the hinder part of the head, a row of con fluent rhomboidal spots running zigzag along the upper surface of the whole length of the body and tail, and a row of small irregular, almost black, triangu lar spots on each side. The under parts
are of a lead color. The characteristic markings are almost invariable, but the ground color varies considerably, from nearly olive, rich deep brown, or brown ish-yellow, to almost black. Thus in some parts of England a black viper is occasionally met with; its ground color a rich black, and the markings of a more intense black than the rest. There is also the "red" and the "blue-bellied," and an almost white viper, with black mark ings. The viper seldom exceeds two feet in length. It feeds on mice, frogs, small birds, and other small animals, which are killed by its poison fangs, and swal lowed entire. It hibernates during several months of the year, and several may then be found twined together in a torpid state. It is a good swimmer, and may occasionally be seen on lakes, such as Loch Lomond, crossing from one is land to another. The young are pro duced in early summer, from 10 to 15 or more at a birth. The eggs have soft, thin envelopes, and are hatched within the oviduct. The young viper is coiled up so closely in the egg as to appear almost a solid mass, but the moment it is set free it is active, and ready to throw itself at once into an attitude of defense.