42 



GUIDE TO EEPTILES AND AMPHIBIANS. 



3. Trionychoidea, or those with very flat oval or almost round 

 shells, covered with soft leathery skin, and broadly webbed 

 limbs, of which only the three middle toes are clawed. 



The following: table shows the chief sub-divisions of the group : 



Order CHELONIA. 



I. Section Athece. 

 Family Spliargidw, or 



Dermochelydida'. 



II. Section Thecophora. 

 i. Sub-order Cryptodira. 

 Family Chelydridw. 

 ., Dermatemydidfc. 

 ., Cinostemidce. 

 „ Platysternidce. 

 ., TestudinidiB. 

 ChelonidcR. 



ii. Sub-order Pleurodira. 



Family Pelomedusida-. 



,, Ghelydidcb. 



Carettochelydidm. 

 Plesioclwlydida>.) Ex- 

 ,, Miolaniidce. jtinct. 



iii. Sub-order Amphichelydia. 

 Family PUurosternidm 



(extinct). 



iv. Sub-order Tricwychoidea. 



Family Triony chides,. 



Pig. 43. 



Upper (A) and Lower (B) Shells of the Green Turtle (Chelone mydas), to 

 arrangement of the horny plates. 



Nuchal. 



sc. Supracaudal. 



g. Gular. 



a. Abdominal 



Vertebral. 



im. Inframarginal. 



h. Humeral. 



/. Femoral. 



Costal. 



ig. Intergular. 



p. Pectoral. 



an. Anal. 



Marginal. 









