1 2 Curtis C. Bentley and James L. Knight 



distally, and the articulating surface of the epiplastron and hyoplastron between 

 the entoplastron and the outside edge is wider in C. picta. Trachemys and 

 Pseudemys are larger and more robust than C picta as adults. Young specimens 

 of Trachemys and Pseudemys can be separated by a less pronounced or inflated 

 scute overlap area and signs of incomplete ossification. 



Hypoplastron - The inguinal sulcus runs diagonally to the peripherals 

 and into the inguinal notch in Chrysemys but is parallel to the peripherals in 

 Clemmys. This element can be distinguished from Deirochelys as it is less elon- 

 gate with respect to width in C picta, and the scute overlap area is wider. It can 

 also be separated from Terrapene Carolina and Emydoidea by the lack of a hinge. 

 Adult Trachemys and Pseudemys differ in being larger and more robust than 

 adults of C. picta. Young specimens of Trachemys, comparable in size to adult 

 C. picta and completely ossified, can be separated from C. picta by a larger 

 bridge with respect to the hypoplastron proper and a greatly reduced or absent 

 epidermal attachment scar. 



Entoplastron - The humero-pectoral sulcus does not cross the entoplas- 

 tron as in eastern species of Clemmys and in Terrapene Carolina. It can be tenta- 

 tively separated from Pseudemys, Trachemys, and Emydoidea by overall size, as 

 specimens of the preceding genera tend to exhibit incomplete ossification when 

 of comparable size to adult C. picta. However, size alone is not a reliable char- 

 acter for this element. We were unable to separate this element from that of 

 Deirochelys, so entoplastra are only tentatively assigned to C. picta. 



Epiplastron - This element differs from other species (except Trache- 

 mys) in that the anterior edge exhibits a degree of serration. This element often 

 is serrated in specimens of Trachemys, but the size of these specimens allows 

 easy separation from C. picta. Young specimens of Trachemys generally lack 

 this serration and have a poorly developed scute overlap area in comparison to 

 C. picta of comparable size. 



Xiphiplastron - This element can be separated from Clemmys, Ter- 

 rapene, and Emydoidea by the scute overlap area, which in those genera is more 

 pronounced than in C. picta. Further, Clemmys muhlenbergii has a posterior 

 edge tapered to a point, while in Clemmys insculpta the element is longer with 

 respect to width, with a pronounced notch where the anal sulcus wraps over the 

 edge, a condition minimal or lacking in C. picta. In C picta the scute overlap of 

 this element is wider and more pronounced on the posterior edge than on any 

 examined specimens of Deirochelys. This element in Trachemys is generally 

 more robust in adult specimens than in C. picta, and in young specimens of com- 

 parable sizes the scute overlap area is much less pronounced than that of C picta. 



2nd Costal - This element differs from C guttata in being approxi- 

 mately 30% wider with respect to length, and the junction between the 2nd ver- 

 tebral sulcus and the 1st and 2nd pleural sulcus is located generally more distal- 

 ly than in C. guttata. This element differs from C. muhlenbergii by having a 



