No true teeth; but the jaws covered with a lamellated substance resembling ivory, either entire, or divided in the middle by a suture: opercle small; branch-iostegous rays five on each side; both deeply concealed.

68. Tetrodon

Jaws divided in the middle, so as to present the appearance of four teeth, two above and two below: skin rough, with small slightly projecting spines: body capable of inflation.

69. Orthagoriscus

Jaws undivided: body very much compressed, short, truncated behind; rough, but without spines; not capable of inflation: dorsal and anal fins high and pointed, uniting with the caudal.