The bone, or principal bone, of the lower jaw; the inferior maxilla; -- also applied to either the upper or the lower jaw in the beak of birds.

The anterior pair of mouth organs of insects, crustaceaus, and related animals, whether adapted for biting or not. See Illust. of Diptera.

The chewing structures of the insect mouth.

The third cephalic appendage, and first mouthpart appendage of isopods. It generally has a lateral three-articled palp and is made up of the following functional regions: incisor process, spine row, molar process, dorsal condyle, and posterior articulation.