THE REPTILES 



185 



widely different lives. Nevertheless all are constructed 

 upon much the same plan. 



176. The lizards (Sauria). As in the amphibians, es- 

 pecially the salamanders, the body (Fig. Ill) consists of 

 a relatively small head united by a neck to the trunk, 



FIG. 111. Common lizard or swift (Scelop&rus undulatus). Photograph by W. II. 



FISHER. 



which, in turn, passes insensibly into a tail, usually of con- 

 siderable length. Two pairs of limbs are almost always 

 present, and these exhibit the same skeletal structure as 

 in the amphibians; but in their construction, as in the 

 other divisions of the body, we note a grace of propor- 

 tion and muscular development which enable the lizards 

 to execute their movements with an almost lightning-like 

 rapidity. The mouth is large and slit-like, well armed with 

 teeth, and the eyes and ears are keen. Scales of various 



