Next, Cuvier identifies the taxonomic divisions of the group, in this case four orders of reptiles, the chelonians (tortoises and turtles), saurians (lizards), ophidians (snakes) and batracians (amphibians, now considered a separate class of vertebrates), describing each group in a single sentence. Thus the batracians are said to have a heart with a single atrium, a naked body (with no scales), and to pass with age from being fish-like to being like a quadruped or biped.
