REPTILES. 3 1 1 



food. All of these occur in the warmer Atlantic, the tortoise-shell ranging 

 to the Indian Ocean, and all occasionally occur on our shores. Testudi- 

 NID^, carapace strongly arched ; plastron very broad ; five toes in front, 

 four behind. Terrestrial, represented in southern U. S. by the gopher 

 turtle, Xerobates polyphemus. Here also belong the giant tortoises (Tes- 

 tudo elephaniopus, etc.) of the Galapagos Islands and Mozambique, and 

 the colossal fossil, Colossochelys atlas, of the upper miocene of India, 

 which was 18-20 feet long, the carapace being 8 feet high. Kinoster- 



FiG. 307. Snapping-turtle, Chelydra serpentina, from Huxley. 



NID.E with free toes, short tail; 9 or II plates on plastron, with our mud- 

 turtle {Kinosternoti pennsylvanicum) and our musk-turtles (Aromockelys). 

 Emyd/E with 12 plates on plastron, including about 80 species, among 

 them the wood and spotted tortoises (^Chelopus), the painted turtle {Chrys- 

 emys), the box-turtles (Cistudo) with hinge in plastron, and the various 

 terrapins, including the famous 'diamond back ' (Malaclemmys pabtstris). 

 Chelydrid^ with long tail, and 9 plates on the plastron. Embraces three 

 species, two, the snapping-turtle {Chelydra serpentina) and the alligator 

 snapper {Macrochelys lacertina) being the fiercest of reptiles inhabiting the 

 U. S. The Cryptodira are found in all ages from the Jurassic down. 



Sub-Order 5. Pleurodira. 



Turtles with epidermal scales ; carapace united to skeleton ; marginals 

 present ; caudal ribs articulated to centrum ; descending process of parie- 

 tals present ; neck bending horizontally ; pelvis anchylosed to carapace 

 and plastron ; plastron always with 13 epidermal plates. ^ Contains over 50 

 species confined to the southern hemisphere, mostly South American, among 

 them Podocnemis, Chelys, Pelomedusa. Sternothcerus is African. While 

 the living forms are very distinct, the fossils show intergradations between 

 the Cryptodira and Pleurodira. Proganochelys, triassic of Germany ; Both- 

 remys, upper cretaceous of New Jersey. 



1 Except in Carettochelydae, in which epidermal plates are lacking. 



