VEKTEBRATA 



63 



lilting by bodies; pelvis anchylosed to 

 carapace and plastron ; marginal bones 

 present and connected with ribs; Pleui-odira. 



The Athccpe includes the single family of the Dermo- 

 chelyda\ 



The Trionychoidea includes only the Trionychidfc. 



The Cryptodira embraces the Cheloniidte, Testudinidai 

 (Fig. 18), Cinosternidse, Dermatemydidas, Clielydridfe, 

 Baenidfe, and Adocidce. 



The Plcurodira includes the the Pleurosternidse, Steruo- 

 theridfe; Pelomedusidee, Plesiochelydidee, Chelydidfe, and 

 Carettochelydidse. 



The earlier tortoises are intermediate in character be- 



Fig. IS.—Testudo laUcuneus Cope ; carapace, from above, one-fourth natural size. 

 From tlie White River Neocene bed of Nebraska. 



