312 POPULAR HISTORY OF THE AQUARIUM. 



cepting that it looks a little brighter and fresher at first ; but 

 in a few days even this difference is no longer observable. 



In eating fish, which constitutes a considerable propor- 

 tion of the food of the carnivorous Testudinata, they will 

 almost always reject the air-bag, which, floating on the 

 surface of the water, tells its tale of the murder which has 

 been committed. This circumstance is so well known, that 

 those who seek the Tortoises are guided in their estimate of 

 the comparative number of those inhabiting any particular 

 lake or pond they may visit by the number of these tell- 

 tale air-bags floating on its waters. 



Mud Tortoises. 



The Trioni/chida have no horny plates covering the shell, 

 but are invested with a strong coriaceous skin ; there is a 

 free flapping edge of a leathery substance at the sides. They 

 burrow in the mud at the bottom of rivers and lakes ; and 

 by means of their very long necks can instantaneously 

 seize their prey without the necessity of moving from their 

 position. 



" They aid the separation of their food, which they seize 

 with their jaws, by tearing it with their long sharp claws. 

 Thus they pursue, seize, and tear in pieces living frogs and 



