154 IOWA ACADEMY OF SCIENCE 



Plastron yellow with a long, more or less symmetrical blackish patch at 

 center. . 

 Shields with narrow yellow margins. 



G. marginata Agassiz. 



Shields traversed by vein-like yellow lines. 



C. belli Gray. 



CISTUDO. 



Carapace not keeled; marked with grouped yellow dashes. 



C. ornata Agassiz. 



Carapace keeled; black or brown with variously developed spots. 



C. Carolina L. 



