Emydosaurians
Have the head large, covered with a thick skin, ears closed with two valves, gape very wide, tongue short, jaws with a single series of cone-shaped teeth inserted in sockets; back with a hard disc formed of a longitudinal series of square keeled plates of hard bony consistence embedded in the skin; the under surface covered with smooth thin square plates; legs short, feet webbed, with four to five toes, the three inner toes of each foot only armed with claws.
They are divided into two groups:—
I. Crocodilidæ, having the lower canines fitting into a notch in the edge of the upper jaw.
II. Alligatoridæ, having the canines fitting into a pit in the upper jaw.]