158 EEPTILBS. 



a Mouth very dilatable ; bones of mandible united by liga- 

 ments ; limbs wanting or represented only by short sptu-s 

 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 sht>rt, 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. TESTCDiKiDiB, 66. 

 If Toes well developed, spreading, and in aquatic species 

 webbed ; claws usually 5-4. 

 t Shell highest at about the middle, usually somewhat de- 

 pressed, the margin flaring outwards; epidermal plates 

 bf the large plastron 13 in number. . EMYDiDiE, 67. 

 XX Shell highest behind the middle ; margin of carapace 

 turned rather downward or inward; plates of plastron 

 7, 9 or ll^-never 12 ; size small. . CDrosTBRNiD^, 68. 

 iXX Shell highest anteriorly; carapace flaring outward, its 

 margin toothed behind; plastron small, cross-shaped 

 with 12 plates and three accessory ones on each side ; 

 jaws powerful, strongly hooked; neck and tail long, 

 the latter with a crest of tubercles ; size large. 



CHBLTDBID.ffi:, 69. 



** Much depressed ; carapace and plastron covered with a leathery 

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

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



Triontchid^, 70. 



0. FAMILIES OF LACERTILIA. 



* Tongue thick, convex, attached at its base to the gullet; scales 



usually more or less spinous. . . . lauAOTDiE, 71. 

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

 t Limbs rudimentary, concealed beneath the skin ; sides with 



a longitudinal fold Ajsoxtcdm, 73. 



If Limbs four — ^well developed. 

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



SciKcii).a!, 74. 



