162 REPTILES. 



*** Carapace rather depressed ; plastron wide, flat, movable upon 

 the carapace and also upon a transverse hinge; anterior 

 lobe somewhat smaller than the posterior, which is emargi- 



nate behind ; toes webbed EMYS, 4 



**** Carapace rather flat ; plastron wide and flat, as is also the 

 bridge connecting it to the carapace ; toes broadly webbed ; 

 hind-legs much stouter than fore-legs ; larger species, deci- 

 dedly aquatic. 



f Upper jaw not notched in front ; carapace more or less strongly 

 keeled or tuberculated. . . . MALACOCLEMMYS, 6. 

 ft Upper jaw notched in front; shell not keeled in adult. 

 $ Horizontal alveolar surfaces of jaws not divided by a longi- 

 tudinal ridge; stripes on neck, tail, legs, etc., bright red 

 (in our species) ; head with yellow lines ; large plates of 

 carapace plain ; marginal plates with bright red mark- 

 ings; a small tooth on each side of notch in upper jaw; 



shell never keeled CIIRYSEMYS, 5. 



\\ Horizontal alveolar surfaces divided by a longitudinal 

 ridge, running parallel with the cutting edge; stripes on 

 legs, etc., usually yellow, never bright red; large plates 

 of carapace often variegated; traces of a keel usually 

 evident, at least in the young. . . PSEUDEMYS, 7. 



/. CISTUDO, Fleming. Box TURTLES. 



1. C. clausa, (Gm.) COMMON Box TURTLE. Colors 

 very variable, chiefly blackish variegated with yellowish; 

 N. Y. to Mo. and S. in dry woods. 



Var. triunguis, (Ag.) Cope. THREE-TOED Box TURTLE. 

 Hind-feet mostly 3-toed, paler. Southern, N. to Perm. 



2. C. ornata, Ag. NORTHERN Box TURTLE. " Shell 

 round, broad, flat, without keel, even when young." 

 Iowa and W. 



2. CHELOPUS, Rafinesque. WOOD TURTLES. 



* A deep notch in upper jaw, with a lengthened tooth on each 

 side of it ; lower jaw strongly arched upwards. (Calemys, Ag.) 



