162 CHELONIANS. 



or sand, like the Land Tortoises, the place chosen being generally 

 situated on the banks of some secluded stream; the number of 

 eggs increasing as the animal approaches maturity. 



The Elodians are divided into Cryptoderes and Pleuroderes : 

 the former distinguished from the latter by the retractile power 

 they possess of concealing their cylindrical neck, with its sheath 

 of loose skin, under the middle of the carapace ; the head, whose 

 width is nearly equal to its height at the occiput ; the eyes always 

 lateral, and their orbit so large that the diameter of the cavity 

 nearly equals a fourth of the whole cranium ; and the jaws, which 

 are strong, sometimes trenchant, in others are dentated on the edge. 

 In the larger number of species the anterior extremity of the upper 

 beak is notched with a strong tooth on each side, producing the 

 appearance of a beak closely resembling that of birds of prey. 



Fig. 36. Mud Tortoise (Cistudo Europced). 



The Mud Tortoises, Cistudo, sometimes called the Yellow Tor- 

 toise (Fig. 36) are very abundant in Europe. They are found in 

 Greece, Italy, Spain, Portugal, and in the southern provinces of 

 France ; also in Hungary, Germany, and as far north as Prussia. 

 They inhabit lakes, marshes, and ponds, at the bottom of which 

 they bury themselves in the mud. Occasionally they come to the 

 surface of the water, and remain there for hours. They live 

 principally upon insects, mollusks, aquatic worms, and small 



