Stomach generally provided with chitinous or calcified masticatory plates.
The mouth lying far back, so that the basal segments of all the prosomatic appendages, excepting those of the 1st pair, are capable of acting as masticatory organs.
The chief purpose for which betel nuts are cultivated and collected is for use as a masticatory, - their use in this form being so widespread among Oriental nations that it is estimated that onetenth of the whole human family indulge in betel chewing.
In the nauplius larva they lie rather at the sides than in front of the mouth, and their basal portion carries a hook-like masticatory process which assists the similar processes of the mandibles in seizing food.
The mandibles, like the antennae, have, in the nauplius, the form of biramous swimming limbs, with a masticatory process originating from the proximal part of the protopodite.