158 REPTILES. 



ft Mouth very dilatable ; bones of mandible united by 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^K, 66. 

 f f 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 ftaring outwards ; epidermal plates 

 of the large plastroL 12 in number. . EMYDID.E, 67. 

 %$ Shell highest behind the middle ; margin of carapace 

 turned rather doM'nward or inward ; plates of plastron 

 7, 9 or 11 nevei 12; size small. . CINOSTEKNID.E, 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 with a crest of tubercles ; size large. 



CHELYDRID/E, 69. 



** Much depressed ; Carapace 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, convex, attached at its base to the gullet ; scales 



usually morb or less spinous. . . . IGUANID^E, 71. 

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

 f Limbs rudinibntary, concealed beneath the skin ; sides with 

 a longitudinal fold. .... ANGUID^E, 72. 

 ff Limbs four -vvell developed. 



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



SCINCID^E, 74. 



