Its brain and ears are highly developed. There are several species of dolphins. Some have blunt rounded heads but in most kinds the jaws are elongated to form a beak. On one they resemble a pair of flat paddles. The bottle-nosed dolphin, so common along our Atlantic coast, becomes from 8 to 12 feet long.
Porpoises are smaller and have blunt snouts.
From 5 to 8 feet long, it has a conspicuous triangular back fin. Argonne National Laboratory, Division of Educational Programs, Harold Myron, Ph.D., Division Director.