158 BEPTILES. 



\\ Mouth very dilatable ; bones of mandible united Dy liga- 

 ments ; limbs wanting or represented only by snort spurs 

 on the sides of the vent Ophidia, V. 



T. FAMILIES OF TESTUDINATA. 



* Carapace firm, not flexible at the margins, not greatly depressed ; 



both shields with well-developed horny plates. 



f Toes short, bound together by the integument ; legs and feet 

 short, club-shaped ; carapace very convex ; plastron cover- 

 ing nearly all of under surface of body ; caudal shields 

 united; claws blunt, 5-4; terrestrial. TestudiniD/E, 66. 



ff Toes well developed, spreading, and in aquatic species 

 webbed; claws usually 5-4. 



:j: Shell highest at about the middle, usually somewhat de- 

 pressed, the margin fiaring outwards ; epidermal plates 

 of the large plastroL 12 in number. . EMYDiDiE, 67. 



X\ Shell highest behind the middle ; margin of carapace 

 turned rather downward or inward ; plates of plastron 

 7, 9 or 11 — never 12; size small. . Cinosteiinid^, 68. 



\\% Shell highest anteriorly; carapace flaring outward, its 

 margin toothed behind; plastron small, cross-shaped 

 with 12 platey and three accessory ones on each side; 

 jaws powerful, strongly hooked; neck and tail long, 

 the latter w^th a crest of tubercles ; size large. 



Ciielydrid^, 69. 



** Much depressed ; -oarapace and plastron covered with a leathery 

 skin, and flexible at the margins ; no horny plates ; fleshy 

 lips; snout piolonged; toes 5-5, but claws 3-3. 



, Trionychid^, 70. 



U. FAMILIES OF LACERTILIA. 



* Tongue thick, cc^nvex, attached at its base to the gullet; scales 



usually morb or less spinous. . . . Iguanid^, 71. 

 ** Tongue flat, elongate, bifid at the end; scales never spinous. 



f Limbs rudimbntary, concealed beneath the skin ; sides with 

 a longitudinal fold Anguid^, 72. 



ff Limbs four — >vell developed. 



X Scales of the belly rounded, arranged in quincunx order. 



SCINCID^, 74. 



