PRIMARY DIVISIONS OP THE CHELONIDES. 113 



every one {fig. 30.). They may be likened to frogs, so 



_ enveloped in homy 



30 ,„^^fe;^-Tr-^^^.^i^%^ armour^ as to restrain 



them from jumping. 

 Their gait is prover- 

 bially slow, their fa- 

 culties dull, and they 

 seem the least intelligent of all vertebrated animals. 

 The head (fig. 3 1.) is not unlike that of a serpent's ; and 

 although not furnished with teeth, the edges of the 

 jaws are so sharp, and their muscular force so strong, 

 that they are capable of separating a finger by their bite. 

 This, in short, is their only means of offence, while they 

 are protected from all enemies but man by the hardness 

 and compactness of the shell, into which they withdraw 

 on the approach of danger. The food of these curious 

 reptiles is as various as their forms and habits. We shall 

 therefore shortly enumerate the principal divisions of 

 the whole tribe, arranging them in the following order : 

 —1 . The TestudinidcB, or land tortoises; 2. The EmydcB, 



or freshwater tortoises ; 3. 

 The ChelydridcB, or crocodile 

 tortoises ; 4. The Trionicidce, 

 or soft tortoises ; and 5. The 

 ChelonidcB, or sea turtles. This 

 series, founded upon what we 

 consider to be the natural or 

 continuous affinities of each, we shall now enter upon 

 in more detail.* 



(116.) The true Testudinid(B, or land tortoises, feed 

 only upon roots and vegetables : during the summer they 

 live in woods or among herbage, and pass the winter, in 

 cold climates, beneath the earth, where they burrow and 

 sleep : the feet are short and clubbed, shaped somewhat 



* The quinary arrangement of Mr. Gray, contained in his valuable Sy- 

 nopsis ReptUium, is somewhat different from this; the groups are there 

 arranged in the following order : Testudinidcs, Emydce, Chelydce, Trionicida; 

 and ChelonidcB. 



VOL. II. 



