Chelonia, or Turtles.

Distinguished by the double shield in which their bodies are enclosed, whether they are terrestrial, fresh-water, or marine.

The Turtles, Chelonia, have the limbs natatory.
Mud Turtles, Trionyx,} limbs amphibious.
Terrapens, Emys,
Tortoises, Testudo, limbs terrestrial.