genus of venomous, desert-dwelling snakes of the viper family, Viperidae. There are two species, the horned viper (C. cerastes), which usually has a spinelike scale above each eye, and the common, or Sahara, sand viper (C. vipera), which lacks these scales. Both species are small (seldom more than 60 cm 【about 2 feet】 long), stocky, and broad-headed and are found in northern Africa and the Middle East.

These vipers are pale, sand-coloured snakes marked with dark spots or crosswise bars. They habitually bury themselves in the sand to protect themselves from the Sun and heat and also to lie in ambush for their prey of lizards and small mammals. Like certain other desert snakes, they travel by sidewinding—i.e., by moving obliquely across the sand. Their venom is relatively weak and is seldom fatal to humans.