TURTLES. 



303 



only at the very edge, so that these unwieldy animals have often been described 

 as destitute of a tongue. The face has no lips, hence the long and close array 

 of grinning teeth is always visible, imparting a very repulsive aspect to the 

 countenance. The strong bony scales forming their coat of mail are frequently 

 ridged, and those of the tail are elevated into a deeply notched or saw-like 

 crest, which at the basal part is double. 



ORDER CHELONIA* 



The Chelonian Reptiles are distinguishable at the first glance 

 by the double buckler wherein their body is enclosed, leaving 

 only the head, neck, tail, and four feet moveable. 



The upper buckler, named the carapax, or back-plate, is formed 

 by the ribs, eight pairs in number, which are widened, united to- 

 gether, and solidly fixed to the back-bone. The lower buckler, 

 termed plastron, or 

 breast-plate, is form- 

 ed of pieces that re- 

 present the sternum, 

 nine in number. A 

 framework usually 

 composed of bony 

 pieces surrounds the 

 carapax, and con- 

 nects all the ribs to- 

 gether. The verte- 

 brae of the neck and 

 tail only are move- 

 able, and the bones 

 of the shoulder and 

 pelvis are literally 

 situated inside the 

 body. The outer surfaces of the carapax and plastron are covered 

 with a series of horny or sometimes leathery plates, of regular 

 angular forms, closely fitted to each other. The jaws are clothed 

 in horn, like the beak of a bird, which they much resemble both 

 in appearance and action. The eggs of the Chelonians are co- 

 vered, like those of birds, with a hard, brittle, white shell, and are 

 deposited by the female in the warm sand, where they are hidden 

 from observation and left to be hatched by the heat of the sun. 



Tortoises possess amazing tenacity of life : some have been 



FIG. 331. SKELETON OF TCRTLE. 



chelone, 



