One of the mouth appendages of Crustacea, situated next behind the maxillæ. Crabs have three pairs, but many of the lower Crustacea have but one pair of them. Called also jawfoot, and foot jaw.
Paired appendage on the posterior and ventral edge of the cephalon. Actually it is the first thoracic appendage, but its body somite is fused into the cephalon, and it is modified for feeding. It consists of the following functional parts: coxa, basis bearing a flattened and setose endite, palp with 5 segments (ischium, merus, carpus, propodus, dactylus), and epipod attached laterally to the coxa.