doubt that the action of these appendages in removing the sand from under the carapace is reinforced by the fanning action of the respiratory appendages, which set up a current that helps to wash the particles away. But the posterior walking legs are not the only organs used in burrowing. The Rev. Dr. Lockwood,[215] who observed the habits of _L. polyphemus_ off the New Jersey coast, says, “The king-crab delights in moderately deep water, say from two to six fathoms. It is emphatically a burrowing animal, living literally in the mud, into which it scoops or gouges its way with great facility. In the burrowing operation the forward edge of the anterior shield is pressed downward and shoved forward, the two shields being inflected, and the sharp point of the tail presenting the fulcrum as it pierces the mud, whilst underneath the feet are incessantly active scratching up and pushing out the earth on both sides. There is a singular economy of force in this excavating action; for the doubling up or inflecting and straightening out of the two carapaces, with the pushing purchase exerted by the tail, accomplish both digging and subterranean progression.” At night-time _Limulus_ is apt to leave the sand and progress by a series of short swimming hops, the respiratory appendages giving the necessary impetus, whilst between each two short flights the animal balances itself for a moment on the tip of its tail. During this method of progressing the carapace is slanting, forming an angle of about 45° with the ground. The unsegmented tail is also used when a King-crab falls on its back. “The spine is then bent, _i.e._ its point is planted in the sand so that it makes an acute angle with the carapace, which is then so far raised that some of the feet are enabled to grasp a projecting surface, either longitudinal or vertical, or at some combination of the two; and the crab then turns over.” [Illustration: FIG. 154.—A sagittal section of _Limulus_, seen from the right side, somewhat smaller than natural size. After Patten and Redenbaugh. All the prosomatic appendages, except the chelicera (4) and chilarium (33) of the right side, are omitted. The genital operculum (32) and the five gills (28) are represented. The muscles are omitted except the fibres running from the occipital ring to the posterior side of the oesophagus, the chilarial muscles, the sphincter ani (27), and the levator ani (24). The endosternite (34), with the occipital ring and the capsuliginous bar, is seen from the side, and the positions of the abdominal endochondrites (31) are indicated. The mouth (1) leads into the oesophagus, which passes through the brain to the proventriculus (12). A constriction, which marks the position of the pyloric valve, separates the proventriculus from the intestine (23) which passes posteriorly to the anus (26). A pair of hepatic ducts (15) enter the intestine opposite the endocranium.