THE LIZARD 363 



occurs on the Atlantic coast as far north as Long Island. 

 From the hawkbill turtle (Fig. 340) comes the tortoise-shell 

 used in certain ornaments. In the " leatherback " the shields 

 are incompletely ossified. 



The family of soft-shelled turtles includes certain turtles 

 that live in rivers or ponds of the Mississippi Valley and the 

 Gulf drainage basin (Fig. 341). They 

 have a flat, rounded shell, the feet are 

 broadly webbed, and the neck is long. 

 Although the ancestors of turtles were 

 without the hard shell, it seems prob- 

 able from the whole structure of the 

 upper and lower plates that the soft- 

 shelled turtles are not ancestral, but of 

 recent origin, and have recently lost ''•\'*v.'i->'-"^-'^"' 

 the hard shell of their ancestors. , > ' 'rf' J^'^'k 



The family of fresh-water and land '\' - *■ I v--^' 



tortoises is known as Testudinidse.^ '([^^^ ^ 'W0' 

 Our snapping-turtle is distributed Fio. 34i. — Trionyx, three- 



(. /-^ 1 , _L ■ T o j-i, clawed turtle of the Mis- 



from Canada to equatorial South .j^^ipp; Vaiiey. Reduced. 

 America. It feeds on fish, and lays From Leunis. 

 from forty to fifty eggs, which it buries at a depth of 

 about a metre (Fig. 342) . The alligator snapper of the Gulf 

 States attains the length of a metre, and is regarded as 

 the "most ferocious and, for its size, the strongest of 

 reptiles." The box-tortoises occupy the northeastern and 

 central parts of North America. They are well known by 

 the fact that the body is short and high, the plastron is pro- 

 vided with a movable hinge, and the carapace is colored 

 black and yellow.^ 



1 From testa, a shell. ^ pig. 343. 



