INTRODUCTION. XV 



toises and Crocodiles, we have the following orders of this 

 class ; — namely, Testiidinata, Enaliosauria, Loricata, and 

 Sqnamata, the last including the true Saurians, the true Ser- 

 pents, and the intermediate group, the Saurophidia of Gray. 

 For convenience sake, however, and because the present work 

 is scarcely a fit arena for the discussion of disputed methods 

 of arrangement, I prefer adopting, for the present popular 

 purpose, the more usual one to which I have before alluded. 



The first of the orders, the Testudinata, includes the Tor- 

 toises and Turtles. Although we have no species of this 

 order inhabiting the British islands, yet as there have been 

 occasionally stray individuals of the marine forms brought to 

 our coasts, and even taken alive, and as many species of the 

 land and fresh water forms are often kept living in our 

 gardens and ponds, it may not be uninteresting or inappro- 

 priate to offer a short account of their general organization 

 and habits. Their structure, as has been already observed, 

 differs in a very remarkable manner from that of the rest of 

 the class. The arrangement of the osseous system has al- 

 ready been glanced at ; and it offers the most remarkable 

 tendency to consolidation and strength, to the sacrifice of 

 facility and variety of motion. In the terrestrial forms 

 especially this character is carried to an extreme degree ; the 

 vertebrae, the ribs, and the sternum are all closely and inse- 

 parably united into a compact solid case, in which the whole 

 of the viscera, and, during rest, the head, limbs, and tail are 

 covered and protected. So strong is this shell, both from 

 the thickness and solidity of its parieties, and from the arched 

 form of the superior portion, that in many species it will bear 

 immense pressure without injury. In certain genera, however, 

 this bony box, although still exceedingly strong, has certain 

 parts which are rendered moveable, for the still more com- 

 plete protection of the enclosed organs. Thus in the genus 

 Kinixys^ a terrestrial form, the lumbar portion of the carapax. 



