TURTLES. 87 



carapace is completely bony, and marked by seven prominent longitudinal keels ; 

 but the plastron is much less fully ossified, and carries five similar keels, the 

 unpaired entoplastral bone being wanting. The head, which is covered with small 

 shields, is remarkable for its relatively large size and globose form ; the beak 

 having two triangular cusps situated between three deep notches. The jaws differ 

 from those of the true turtles in being sharp-edged from end to end, without any 

 expanded bony palate ; and there is also an important difference in the structure 

 of the skull itself, which may, however, be apparently the result of specialisation. 

 As in the true turtles, the limbs are converted into flattened paddles, which are, 



LEATHERY TURTLE (^ nat. size) 



however, completely destitute of claws; the front pair being much elongated, 

 narrow, and pointed, while the hinder ones are short and truncated. The humerus, 

 or bone of the upper arm, has the same general form as in the true turtles ; and is 

 thus very unlike the corresponding bone of other members of the order. The 

 process marked h in the figure on p. 88 is more developed than in the turtles ; 

 and the foramen e at the lower end is unique in the order. Largest of living turtles, 

 the leathery turtle exceeds 6 feet in length ; and while in the young the front 

 flippers are equal in length to the shell, in the adult they become shorter. The 

 general colour is dark brown, which may be either uniform, or relieved with 

 yellow spots; the longitudinal tuberculated keels on the shell, as well as the 

 margins of the limbs, being invariably yellow in the young. 



