Monitor

Monitor, an old synonym of Varanus, the typegenus of Varanida; (Water-Lizards), chiefly from the Oriental region, and used also for any individual of the family. They are the largest living lizards; the tail is generally compressed laterally to serve as a swimming organ, and the protrusible tongue ends in two filaments. The Nile Monitor (F. niloticus), from five feet to six feet long, is olive-grey marked with black. The name is due to the belief that these reptiles give warning of the approach of a crocodile by a hiss or whistle. The young of the Indian species is erroneously supposed to be venomous. [Heloderm.]