DIVISIONS OF KEPTILIA. 



247 



chiefly deserve notice from the fact that their eyes are not pro- 

 vided with movable eyelids. The Chameleons, also, cannot 

 be said to possess movable eyelids, for the eye is covered with 



FIG. 123. The Skink (ScincuxofficinaUz) 



a single lid, leaving only a central aperture for the pupil. The 

 common species ( Chameleo Africanus) occurs abundantly in 

 the north of Africa, and has long been known for the changes 

 of color which it has the power of exhibiting. It is a sluggish 

 animal, and catches insects by darting out its long and pro- 

 trusible tongue with extreme rapidity. 



ORDER IV. CROCODILIA. The last and highest order of 

 the living Reptiles is that of the Crocodilia, comprising the 

 Crocodiles, Alligators, and Gavials, and characterized by the 

 following peculiarities : The outer or integumentary skeleton 

 consists partly of horny scales developed by the outer layer 

 of the skin, and partly of large bony plates produced by the 

 inner layer of the skin. The bones of the skull and face are 

 firmly united, and the two halves of the lower jaw are joined 

 by a distinct suture. The teeth form a single row in both 

 jaws, and are implanted in distinct and separate sockets. The 

 front ribs of the trunk are double-headed, and there are no 

 collar-bones. The heart consists of four distinct chambers, 

 two auricles and two ventricles, all completely separated from 



