This is a genus of blind or threadsnakes native to much of South America, Central America, and into Mexico. Variable in appearance with some individuals sporting distinctive colors and patterns while others are the more usual shades of gray or pink-brown that many other blind snakes show, this group of species is defined by a relatively small number of subcaudal scales (those under the tail) and broad supraoculars (scales above the eyes that are wider than they are long in this group).