Cerastes, or HORNED VIPER, a genus of serpents of the family Viperidae, distinguished by a broad depressed heart-shaped head, the scales of which are similar to those of the back, and particularly remarkable for the development of one of the scales of each eyelid into a spine or horn, often of considerable length. The tail is very distinct from the body. This genus is exclusively African, and very venomous. There is probably only one species, Cerastes egypciacus or cornutus, the Horned Viper of the north of Africa, called Cerastes by the ancients, the name being derived from the Greek keras, 'a horn.' It was correctly described by the traveller Bruce, but his description was for some time regarded with incredulity.