190 AFFINITIES AND GEOGKAPHICAL 



voyages they annually undertake, for the purpose of depositing 

 their eggs. It is also found, from our stony records, that the 

 Chelonia were much more widely diffused over the earth in the 

 ages of the oolite and tertiary, than they are now. 



The marine chelonia Turtles (Chelones) demand the first 

 notice. To this group belong the largest existing specimens of 

 the order ; some of them reach six and even seven feet in 

 length, and weigh seven or eight hundred pounds. All of 

 them have extremities modified into paddles, for marine pro- 

 gression, with the toes enveloped in the membrane, and a very 

 slight development of claws ; but there is a natural division of 

 the chelones in respect of habits and even of organization. One 

 sub-group, amongst which is the common Green Turtle, so 

 well known for its palatable qualities, is composed of species 

 altogether herbivorous and of gregarious and innocent 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 in- 

 tervals of cartilage, by which their bodies have a certain 

 flexibility. Another sub-group comprises turtles of carni- 

 vorous 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 j 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 progress 

 of a bird in the air." 



