558 GECKOS. FAMILY IGUANIDJE. 



with the back downwards : they lurk in the chinks and fissures 

 of walls and trees, and in holes and crannies of buildings. From 

 the flatness and flexibility of their bodies, they are capable of 

 insinuating themselves into the smallest crevices ; and there they 

 lurk during the day, coming forth at night in quest of their 

 insect prey, and pursuing it with much activity, occasionally 

 uttering a kind of chuckling cry, from which their name is 

 derived. The Geckos are diffused through the warmer regions 

 of all quarters of the globe ; being most numerous in the 

 tropical portions of Africa. 



494. The family IGUANIDJS, or Iguanas, is a very extensive 

 one ; numbering upwards of 150 species, many of which are 

 among the largest Saurians at present existing, with the excep- 

 tion of the Crocodiles. Of the true Iguanas, which are re- 

 stricted to America, the general aspect will be seen from the 



FIG. 332. IGUANA. 



accompanying figure. They have a crested ridge along the 

 back ; and a curious dewlap, formed by a fold of the skin, 

 under the throat, which is capable of being distended with air. 

 The tail is long and flexible, and is laterally compressed, as in 

 the Crocodiles. The Iguanas are chiefly distinguished by the 

 form and insertion of the teeth ; these are not lodged in distinct 

 sockets, but are fixed along the internal face of the jaw-bone in 

 a sort of furrow, and adhere by one side of the bony substance 

 of the root; the surface of the teeth is irregular, adapting them 

 to grind down the vegetable substances on which these animals 

 feed. They are arboreal in their habits, and feed principally 

 upon vegetable aliment; it appears, however, that they will 



