Miocene. Trachemys Agassiz, Clemmys Ritgen, North America.
Pliocene. Terrepene Merrem, Trachemys Agassiz, ? Clemmys Ritgen, Deirochelys Agassiz, Pseudemys Gray, North America.
Pleistocene. Terrepene Merrem, Chrysemys Gray, Clemmys Ritgen, ? Pseudemys, North America.
Ptychogaster Pomel, Oligocene, Miocene, Europe.
Family Testudinidae. Temporal roof reduced. Neck retractile. Plastron suturally united with the highly arched carapace. Phalanges not more than two in number. Small to very large tortoises, herbivorous, terrestrial.
Eocene. Hadrianus Cope, Achilemys Hay, North America. Testudo, Africa.
Oligocene. Testudo Linné, Stylemys Leidy, North America.
Miocene to Recent. Testudo Linné, North America, Europe, Asia, Africa.
D. Suborder Trionychoidea
Skull and neck as in the Cryptodira, the basiphenoid separating the pterygoids. Plastron ligamentously united with carapace, which lacks the peripheral bones and is covered with a leathery skin only and is flattened. More than three phalanges in third digit. River and lake turtles, the neck long.
Family Plastomenidae. Hyoplastra, hypoplastra, and xiphiplastra closely united. Legs unknown.
Uppermost Cretaceous and Lower Eocene. Plastomenus Cope, North America.
Family Trionychidae. Openings between hyoplastra, hypoplastra, and xiphiplastra. Three claws only, feet elongate.
Uppermost Cretaceous. Helopanoplia Hay, North America.
Eocene. Conchochelys Hay, Axestemys Hay, Aspideretes Hay, Amyda Oken (= Platypeltis Fitzinger), North America.
