204 REPTILIA: TESTUDINATA. XXX. 



piece. The osseous plates, both above and below, correspond neither 

 in number nor position with the overlying dermal plates. 



The skull is more compact than that of the other reptiles. There 

 are no teeth, but the jaws are encased in horny sheaths, usually 

 with sharp cutting edges ; the eye is furnished with two lids and a 

 nictitating membrane as in the birds ; the tympanic membrane is 

 always present, although sometimes hidden by the skin. Respira- 

 tion is effected by swallowing air. (Lat., testudo, tortoise.) 



Families of Testudinata. 



a. Limbs developed as paddles, not capable of distinct movements at wrist or 

 ankle-joint ; digits flattened, elongated, bound immovably together by the 

 integument. (Sea Turtles.) 

 b. Feet scaleless, the anterior very large. . . DERMOCHELYDID^E, 117. 



bb. Feet scaly; carapace heart-shaped CHELONIID^E, 118. 



aa. Limbs not in the form of paddles, capable of movement at wrist and 

 ankle-joints. (Land and pond-turtles.) 



c. Carapace leathery, its margins flexible; no dermal plates; toes 5-5, 

 the claws 3-3; head small, the snout pointed; body very flat. 



TKIONYCHID/E, 119. 



cc. Carapace firm, ossified ; dermal plates present ; claws mostly 5-4. 

 d. Fingers and toes spreading, not closely bound together, more than 



one joint being free. 



e. Tail very long and strong, with a crest of tubercles ; plastron nar- 

 row and small, cross-shaped, with 9 plates (besides the bridge) ; 

 head large; body highest in front. . . . CHELYDKHXE, 120. 

 ee. Tail short, not crested; plastron broad. 



f. Lower jaw ending in a long sharp point ; carapace highest be- 

 hind the middle, its edge not flaring outward; plastron with 9 



or 11 plates KINOSTERNID^:, 121. 



ff. Lower jaw without long point at symphj'sis ; carapace highest 

 at about the middle, its edge flaring outward; plastron with 12 



dermal plates EMYDID.E, 122. 



dd. Fingers and toes bound closely together, only the last joint free; 

 plastron very broad TESTUDINID^E, 123. 



FAMILY CXVII. DERMOCHELYDID^. (THE LEATHER- 

 TURTLES.) 



Sea turtles with the body covered by a smooth leathery skin ; 

 carapace with several longitudinal ridges with deep grooves between 

 them ; body highest in front and widest just before bridge ; hind legs 

 much exposed ; toes without nails ; head short, high, very broad 

 behind ; upper jaw with 2 pits and 2 tooth-like projections. One 

 species, widely distributed. 

 301. DERMOCHELYS Blainville. (Sep/ia, skin; xe'Xvs, tortoise.) 



595. D. coriacea (Vandelli). TRUNK-BACK. LEATHER-TUR- 

 TLE. Dark brown. L. 6 to 8 feet. Open sea, N. to Cape Ann. 

 (Lat., leathery.) (Eu.) 



