While all serpents were lords and guardians of wealth, certain of them were crested, or had small horns, which conveyed the idea of a crowned and imperial snake, the basiliskos. Naturalists have recognised this origin of the name by giving the same (Basiliscus mitratus) to a genus of Iguanidæ, remarkable for a membranous crest not only on the occiput but also along the back, which this lizard can raise and depress at pleasure. But folklore, the science of the ignorant, had established the same connection by alleging that the basilisk is hatched from the egg of a black cock,--which was the peasant's explanation of the word cockatrice. De Plancy traces one part of the belief to a disease which causes the cock to produce a small egg-like substance; but the resemblance between its comb and the crests of serpent and frog [236] was the probable link between them; while the ancient eminence of the cock as the bird of dawn relegated the origin of the basilisk to a very exceptional member of the family--a black cock in its seventh year. The useful fowl would seem, however, to have suffered even so slightly mainly through a phonetic misconception. The word 'cockatrice' is 'crocodile' transformed. We have it in the Old French 'cocatrix,' which again is from the Spanish 'cocotriz,' meaning 'crocodile,'--krokodeilos; which Herodotus, by the way, uses to denote a kind of lizard, and whose sanctity has extended from the Nile to the Danube, where folklore declares that the skeleton of the lizard presents an image of the passion of Christ, and it must never be harmed. Thus 'cockatrice' has nothing to do with 'cock' or 'coq,' though possibly the coincidence of the sound has marred the ancient fame of the 'Bird of Dawn.' Indeed black cocks have been so generally slain on this account that they were for a long time rare, and so the basilisks had a chance of becoming extinct. There were fabulous creatures enough, however, to perpetuate the basilisk's imaginary powers, some of which will be hereafter considered. We may devote the remainder of this chapter to the consideration of a variant of dragon-mythology, which must be cleared out of our way in apprehending the Dragon. This is the agathodemonic or heraldic Dragon, which has inherited the euphemistic characters of the treasure-guarding and crowned serpent.