1920] Tt/rtles of North Carolina 67 



2. Shell without horny plates, covered with a black leathery skin, 

 and with seven longitudinal ridges down back. (1) Leatherback Sea 

 Turtle (Dermochelys coriacea) . 



2. Shell with horny plates without longitudinal ridges. See ^. 



3. Carapace mottled with yellow, and covered with loosely over- 

 lapping plates. Hawksbill Sea Turtle (Eretmochelys imhricata). 

 Tropical and subtropical seas. 



3. Carapace with smooth, not overlapping, plates. See 4. 



4. Claws on front limbs one each, carapace mottled with yellow. 

 (2) Green Sea Turtle {CheJoma mydas). 



4. Claws on front limbs two each, carapace without yellow mot- 

 tling. See 5. 



5. Plates on under side of bridge three. (3) Loggerhead Sea Turtle 

 (Cfl.- etta caretta). 



5. Plates on under side of bridge four. (4) Bastard Turtle {Ca- 

 retta hempi) . 



6. Shell covered with horny plates. See 7. 



6. Shell covered with a leathery skin, form flattened and orbicular. 

 Soft-shelled Turtles (Family Trionychidae). See 37. 



7. Plastron narrow, cross-shaped, the plates of its central portion 

 nine. Snapping Turtles (Family Chelydridae). See 8. 



7. Plastron not narrow and cross shaped, its plates more than 

 nine. See 9. 



8. Under surface of tail with small scales : carapace with three 

 strong keels at all ages. Alligator Snapper {Macrohelys temminckii), 

 Georgia. 



8. Under surface of tail with rather large plates, carapace with- 

 out strong keels in adult. (5) Snapping Turtle (Chelydra serpen- 

 tina). 



9. Plastron with ten or eleven plates : front and hind portions 

 of plastron hinged on fixed central portion and capable of partially 

 closing the shell. Mud Turtles (Family Kinosternidae). See 10. 



9. Plastron with twelve plates : plastron not as in the mud turtles. 

 (Family Testudinidae). See 15. 



10. Plastron comparatively small, hind portion capable of little 

 movement, pectoral plate trapezoidal. Musk Turtles. See 11. 



