SQUAMATA 141 



have come from a common ancestry; among all reptiles the known 

 geological history of the snakes is shortest. 



Lizards, on the other hand, have a very high antiquity, begin- 

 ning, as we now know, at least as long ago as early Triassic times. 

 They still have many primitive characters in their structure and 

 are the least advanced type of reptiles now hving, with the excep- 

 tion of the tuatera. Their remains are seldom found in the rocks, 

 probably because they have always been so strictly terrestrial in 

 habit, for the most part seldom frequenting even the vicinity of 

 the water. The true lizards now hying number about eighteen 

 hundred kinds, classified into about twenty famiUes, divided among 

 four chief groups, of which the chameleons, the amphisbaenas, our 

 common lizards, and the monitors are represeij-t^tives. 



Most hving lizards are inhabitants of warrn climates, though 

 some extend rather far north in the temperate zone. With the 

 exception of New Zealand, and the polar and subpolar regions, 

 lizards are found in all parts of the world. The great majority 

 live only in high and dry places, though some are denizens of low 

 and marshy places, a few even not being averse to the water. 

 They are, for the most part, spry in their movements, some httle 

 ones scarcely six inches in length taxing a vigorous man's speed 

 to capture; and many are expert chmbersof cliffs, trees, and 

 even the ceiUngs of residences. Some, the remarkable little flying 

 dragons of Ceylon, have an extraordinary development of the 

 skin on the sides of the body, supported by the expanded ribs, 

 forming a sort of parachute whereby the creatures can sail con- 

 siderable distances through the air. Nearly all are carnivorous, 

 feeding upon small mammals, birds, other reptiles, frogs, and 

 insects; a few only are herbivorous, such as the iguanas, which 

 are often used for human food. Nearly all hzards are oviparous, 

 laying from two to thirty eggs. In size the great majority are small, 

 less than a foot in length; but some, such as the monitors and 

 iguanas, reach a length of from four to six feet, or even more, and 

 certain extinct monitors of India are known to have attained a 

 length of thirty feet. They are, for the most part, slender, grace- 

 ful, prettily marked, and quite inoffensive creatures. A few are 

 short, flat, or stumpy in shape, such as the so-called homed toad. 



