The bases of the chelicerae do not limit the mouth, but between and behind them is a ridge or tubercle which has the same relationship to the mouth of _Limulus_ that the labrum has in Insects and some Crustacea. Posteriorly the mouth is bounded by the “promesosternite,” a large median plate which lies between the bases of the ambulatory limbs. The pedipalps and all the ambulatory limbs have their bases directed towards the mouth, their gnathobases or sterno-coxal processes are cushion-like structures covered with spines—all pointing inwards—and with crushing teeth. They form a very efficient manducatory apparatus. The boundary of the mouth is finally completed by the chilaria. Certain of the appendages which persist will be described with the functions they subserve, the eyes with the sense-organs, the genital operculum with the generative organs, the gill-books with the respiratory system, but the chelicerae, pedipalpi, and walking limbs, which have retained the functions of prehension and locomotion usual to limbs, merit a little attention.[213] The chelicerae are short and composed of but three joints. They are, like the succeeding segments, chelate, and the chelae of all are fine and delicate like a pair of forceps rather than like a Lobster’s claw. In the female _L. polyphemus_ the pedipalp is remarkably like the three ambulatory legs which succeed it, and all four are chelate, but in the adult male the penultimate joint of the pedipalp is not prolonged to form one limb of the chela, which is therefore absent, and the appendage is thicker and heavier than in the other sex. In _L. longispina_ and _L. moluccanus_ the first walking leg, as well as the pedipalp, ends in a claw and not in a chela; the immature males resemble the females. The first three walking legs in both sexes of _L. polyphemus_ resemble the pedipalpi of the female, and like them have six joints. The fourth and last pair of ambulatory appendages is not chelate, but its distal joints carry a number of somewhat flattened structures, which are capable of being alternately divaricated and approximated or bunched together. This enables them to act as organs for clearing away sand or mud from beneath the carapace as the creature lies prone on the bottom of the sea. To quote Mr. Lloyd,[214] the “two limbs are, sometimes alternately and sometimes simultaneously, thrust backward below the carapace, quite beyond the hinder edge of the shell; and in the act of thrusting, the lobes or plates on each leg encounter the sand, the resistance or pressure of which causes them to open and fill with sand, a load of which at every thrusting operation is pushed away from under the king-crab, and deposited outside the carapace. The four plates then close and are withdrawn closed, previous to being opened and charged with another load of sand; and at the deposit of every load the whole animal sinks deeper into its bed, till it is hidden all except the eyes.” There seems little