DIVISIONS OF KEPTILIA. 



263 



commercial importance, as it furnishes the " tortoise-shell " of trade, 

 so largely used in various kinds of ornamental work. 



Fig. 188 The Hawk's-bill Tuiilo (Chelone imbricata). (After Bell.) 



The Sea-tortoises or Turtles have the carapace much flattened, the 

 legs of unequal length, in the form of solid fins or oars, the toes 

 being conjoined, and hardly distinct from one another. 



The Marsh, Pond, and Eiver Tortoises are generally furnished 

 with webbed feet, and lead an amphibious, .semi-aquatic existence. 

 The so-called " Soft Toi-toises " {Trionycidce) belong here, and are 

 distinguished by the imperfect condition of the carapace, which is 

 simply covered with a leathery skin. A good example is the Soft- 

 shelled Turtle {T ferox) of the Southern States. Here also belong 

 the Snapping-turtles, so well known in the pei-soii of the common 

 American species {Chelydra serpentina), and the Terrapins {Emydidce), 

 of which many forms are found in all parts of the United States. 

 In the curious little Box-tortoise {Ciatudo Yirgmea) the plastron is 

 composed of two movable portions which can be brought into accu- 

 rate apposition with the carapace, thus completely protecting the 

 animal within. 



The Land-toitoises have short legs of nearly equal length, the toes 

 little distinct, and united into a sort of stump, with indistinct, horny 

 claws. Good examples of this group are the common European 

 Tortoise {Testudo Orwca) and the Indian Tortoise (T. Indicd), the 

 la-st attaining a length of over three feet. 



