The Sea Turtles 



Hawk's-bill Turtle are examples of evolution from the 

 modern, fresh-water chelonians; development along the line of 

 adaptation to a strictly marine life has produced a highly spe- 

 cialised form, but the shielded carapace and plastron, and other 

 parts of the structure, show close relationship with the Tes- 

 tudinidcc. Thus the student will appreciate that the family 

 Sphargida — one species, and the Chelonidce — four species, are not 

 alone widely separated in classification, but appeal to one an- 

 other only in a form that is essential to the life the species lead. 

 With this understood, it is not inappropriate to embrace all the 

 sea turtles in a chapter by themselves. This arrangement 

 popularises the subject and makes it possible to construct a 

 general key. 



KEY TO THE SEA TURTLES 



General: Limbs long, flat and paddle-like — Flippers. 



A. Carapace with seven, heavy keels, running length- 



wise; covered with a leathery integument in place 

 of shields. 



Uniform dark brown, or black. 

 LEATHER-BACK TURTLE; TRUNK TURTiE, Sphargis coriacea. 



B. Carapace covered with smooth shields, which do not 



overlap. 

 *Front flippers with two claws. 

 Head very large. Carapace uniform brown or black. 



Alveolar (crushing) surfaces of jaws without ridges — 



under horny sheaths. 



LOGGERHEAD TURTLE, Thalassochelys caretta. 



Head very large. Carapace dark brown or black. Al- 

 veolar (crushing) surfaces of jaws with ridges — under 

 horny sheaths. 

 KEMP's LOGGERHEAD TURTLE, Thalassochelys kempii. 



**Front flippers with one claw. 



Head of moderate size. Carapace olive or brown, 

 mottled with yellow. 



GREEN TURTLE, Chelouia mydas. 



C. Carapace covered with smooth, loosely-overlapping 



shields. 



Upper mandible bcak-Iike. Carapace brown or black, 



mottled with yellow. 



hawk's-bill turtle, Chelonia imhricata. 



