168 AFFINITIES AND GEOGRAPHICAL 



Turtle, so well known for its palatable qualities, is composed 

 of species altogether herbivorous and of gregarious and inno- 

 cent habits. These animals may be seen in herds at the 

 bottom of the sea, quietly browsing on the weeds growing 

 there. Sometimes they enter the mouths of large rivers, and 

 are occasionally seen to make their way ashore, apparently in 

 search of food. Their plates are discoidal, laid edge towards 

 edge, with intervals of cartilage, by which their bodies have a 

 certain flexibility. Another sub-group comprises turtles of car- 

 nivorous habits, active, and when attacked, fierce ; examples are 

 seen in the Loggerhead Turtle, which has the plates arranged 

 as above, and the Hawksbill, in which they are imbricated, or 

 laid edge over edge ; the latter being the animal which fur- 

 nishes the arts with the elegant substance called Tortoise-shell. 

 Finally, there is a genus, also of carnivorous habits, the 

 Sphargis or Coriaceous Turtle, in which the exterior is not 

 composed of shell, but of a leathery skin, having seven tuber- 

 culated ridges passing lengthwise along the back. These 

 carnivorous genera have a more powerful form of mouth than 

 the rest, and in some the claws are more marked. Thus armed, 

 the Loggerhead, for example, will defend itself from a man 

 with courage and ferocity, will snap a walking-cane in twain 

 with one effort of its jaws, and not let go anything it has 

 seized until its own life is extinct. These genera live upon 

 mollusca, Crustacea, and fishes ; and even the young crocodiles 

 are liable to the attacks of the loggerhead. The progression 

 of all the turtles in their proper element is rapid. M. Audubon 

 says " The Green and Hawkbilled, in particular, remind you 

 by their celerity, and the ease of their motions, of the pro- 

 gress of a bird in the air." 



In all the remaining chelonia, the paddle form of the ex- 

 tremities is exchanged for legs and feet, the latter furnished 

 with claws. 



The River Tortoises (Tryonices), conspicuous tenants of 

 the Ganges and Euphrates, the Niger and Nile, the Mississippi 

 and Ohio, are next in size to the Turtles, some being three 

 feet long. With an imperfect development of the osseous 

 case, they are enveloped in a soft skin, which has caused 



