2. (Arthropoda) a. In Chelicerata, the gnathosome of acarines. b. In Crustacea, the anteroventral projection of the free margin of the carapace; not equivalent to rostrum. c. In Insecta, the snout, proboscis, or rostrum; in Homoptera, usually 3-segmented, arising from the ventroposterior of the head and directed backward under the body.
4. (Bryozoa) The avicularia.
5. (Mollusca) a. An angular projection of the apex of an intermediate valve; a mucronate valve; a similar projection of the upper surface of the valve anteriorly and between the sutural laminae is termed a false beak. b. In Bivalvia, noselike angle, along or above the hinge margin, marking the area of shell growth. c. In Cephalopoda, paired horny mandibles.