TESTUDINATA. 113 



Adocid^. 



Cope, Proceedings American PhiloBophical Society, 1870, p. 559. 

 a Vertebral bones and scuta normal. 



One intergular scutum entirely separating the gulars Adocus Cope. 



Either two intergulars, or the gulars meeting behind intergular Amphiemys Cope. 



a a Vertebral bones wedge-shaped, widening upwards ; verte- 

 bral scuta not wider than the bones. 

 Elements of carapace early coossifled Eomorhophus Cope. 



„ ^ , ^ Emydid^. 



a No scutal sutures. 



Surface sculptured Apholidemys Pom. 



a a Scuta including intermarginals and two anals. 



Lobes of sternum narrow Dermatemys Gray. 



Lobes of sternum wide Agomphus Cope. 



a a a Scuta ; two anals, no intermarginals. 



Surfaces of carapace sculptured ; plastron fixed Compsemys Leidy. 



Surfaces of carapace smooth ; plastron fixed ; recent Hmydidce* and 



the genus Emys Brong. 



Posterior lobe of plastron moveable; surfaces smooth Ptycliogaster Pom. 



a a a a Scuta ; One anal, no intermarginals. 



Carapace smooth ; pectoral plates entire Stylemys Leidy. 



Carapace smooth ; pectoral plates small, widely separated from each 



other Manuria Gray. 



„ , . TESTtTDINID^. 



a Two anal scuta. 

 Ten abdominal scuta Hadrianus Cope. 



a a One anal scutum. 



/9 Claws 4-4. 



Jaws with aveolar grooves Testudinella Gray. 



Lower jaw smooth ; upper with a ridge Homopus Dum. Bibr. 



/9 /9 Claws 5-4. 



Y Hinder part of carapace mobile. 

 Gulars distinct Kinixys Wagl. 



;- y Hinder part of carapace fixed. 



S Plastron moveable in front. 

 Gulars distinct Pyxis Bell. 



$ S Plastron fixed. 



Gular plates united Chersina Gray. 



Gular plates distinct. 



Lower jaw with two cutting edges Xerobates Agass. 



Lower jaw with one cutting edge. Testudo Linn. 



The extinct tortoises of the Cretaceous and Eocene throw considerable 

 light on the probable origin of various existing genera,t and while much 



* Gray has distinguished several genera among existing species, on cranial characters. 

 tSee on the Extinct Tortoises of the Cretaceous of New Jersey. Proceed. Amer. Ass. Adv. Sol., 

 1871, p. 344. 



