any of four species of small burrowing snakes of the family Colubridae that have the nose shield enlarged and flattened, with free edges. Several subspecies of each also exist. The two members of the genus Phyllorhynchus are found in creosote-bush deserts of the southwestern United States and Mexico, where they hunt at night for lizards and insects. The two species of the genus Lytorhynchus are abundant in the dry country of northern Africa and southwestern Asia.