CLASS REPTILIA 535 



snout with hooked beak. Examples: Chelydra, 

 Macrochelys (Fig. 444). 



Family 2. KINOSTERNID.E. MUSK- and MUD -TURTLES. 

 CRYPTODIRA possessing a nuchal plate with costi- 

 form processes underlying the marginals ; eight 

 bones in the plastron. Examples : Kinosternon, 

 Aromochelys. 



Family 3. DERMATEMYDID^:. FRESH- WATER TURTLES 

 of Southern Mexico and Central America. CRYPTO- 

 DIRA with nuchal plate as in KINOSTERNID^E; nine 

 bones in plastron. Examples: Dermatemys, Stauroty- 

 pus, Claudius. 



Family 4. PLATYSTERNID.E. CRYPTODIRA without costi- 

 form processes on nuchal plate. Examples: Platy- 

 sternum (a single species, P. megacephalum, in Burma, 

 Siam, and China). 



Family 5. TESTUDINID.E. TORTOISES and most TURTLES. 

 CRYPTODIRA without costiform processes on nuchal 

 plate; lateral temporal arch usually present; no 

 parieto-squamosal arch. Examples: Testudo (Fig. 

 446), Chrysemys (Fig. 445), Emys. 

 Superfamily 2. CHELONIIDEA (CHELONID.E + ATHECA). 

 SEA-TURTLES. MARINE TESTUDINATA with paddle- 

 shaped limbs. 



Family i. CHELONIID.E. Four species inhabiting tropical 

 and semitropical seas (Fig. 447). 



Family 2. DERMOCHELYID.E. The leathery turtle of 



tropical and semitropical seas (Fig. 448). 

 Superfamily 3. PLEURODIRA. TESTUDINATA with neck 

 bending laterally; pelvis fused with the shell. 



Family i. PELOMEDUSID.E. FRESH- WATER TURTLES. 

 PLEURODIRA with neck completely retractile within 

 the shell; carapace without nuchal shield; plastron of 

 eleven bones. Examples: Pelomedusa, Podocnemis, 

 Sternothcsrus. 



