Pl. labra. [L., cogn. w. LABIUM.] A lip or lip-like part. (Cf. LABIUM.) a. In insects, crustaceans, etc.: A part forming the upper border or covering of the mouth. b. Conch. The outer lip of a univalve shell.
1816. T. Brown, Elem. Conchol., 154. Labra, the lip.
1826. Kirby & Sp., Entomol., IV. 381. In the Ephemerina the parts of the mouth except the labrum and palpi appear to be mere rudiments.
1834. McMurtrie, Cuvier’s Anim. Kingd., 301. A mouth composed of a labrum, two mandibles, a ligula, and one or two pairs of jaws, and branchiæ.
1849. Murchison, Siluria, x. (1867), 237. [Pterygotus] The mouth … protected by a large heart-shaped labrum.
1851. Richardson, Geol., viii. 240. The labrum, or outer lip … is the expansion, or continuation of the body of the shell, on the right margin of the aperture.
1880. Huxley, Cray-Fish, ii. 51. In front, the mouth is overlapped by a wide shield-shaped plate termed the upper lip or labrum.
