REPTILES. 199 
which are among the largest of the Lizard tribe. The 
general aspect of the true Iguanas, which are found only 
in America, can be seen in Fig. 161 (p. 198), the Tubercu- 
lated Iguana. They have a long flexible tail, a crested 
ridge along the back and tail, and a dewlap under the 
throat which the animal can distend with air. The Tu- 
berculated Iguana, sometimes reaching even six feet in 
length, is found in South America and the West Indies. 
With this family is allied the fossil Iguanodon, whose re- 
mains show that it could not have been less than forty 
feet in length. A very harmless little Lizard, with the 
terrible name of Flying Dragon, may be considered as 
belonging to this family, because it has the characteristic 
scales of the Iguanas and the dewlap. It has, like the 
Flying Squirrel, a wing-like expansion of the skin on each 
side of the body, and uses it for a similar purpose. Some 
of the ribs of the animal extend out as a frame-work to 
these wings. When running about on the branches of a 
tree they are folded to the side, but when it wishes to go 
from one tree to another, or to descend to the ground, 
it raises the ribs, thus expanding the so-called wings. 
This animal is found in the Asiatic Archipelago. 
327. The remaining families of Lizards have slen- 
der tongues, which are also more or less forked. The 
family of Monitors includes some of the largest of the 
Lizards. They are graceful and agile animals, living on 
large insects, eggs, birds, small Mammalia, reptiles, and 
fish. The Monitor of the Nile, which is about six feet 
long, is very destructive to the eggs and the young of the 
Crocodile. Its name of Monitor is derived from the hiss- 
ing noise which it makes when it sees a Crocodile ap- 
proaching, thus giving a warning to any one that hap- 
pens to be near. There are Monitors, also, in this coun- 
try, which give a similar warning of the approach of the 
Alligator. 3 
328. The true Lizards are bright-eyed, slender, and 
lively little animals, with brilliant colors, especially those 
