CLASS REPTILTA 535 



snout with hooked beak. 'Examples: CJiclydra, 

 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, 



Aromochdys. 



Family 3. DERMATEMYDID.E. - - FRESH-WATER TURTLES 

 of Southern Mexico and Central America. CRYPTO- 

 DIRA with nuchal plate as in KINOSTERNID^:; nine 

 bones in plastron. Examples: Dermatemys, Stauroty- 

 pus, Claudius. 



Family 4. PLATYSTERNID^;. 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 (CHELONKME -f- 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 ot 

 eleven bones. Examples: Pelomedusa, Podocmmis, 

 Sternothcerus. 



