Let us now see what use the creature can make of these numerous and varied pedal appendages, and for distinctness' sake we shall call the anterior set thoracic and the posterior abdominal. When placed in shallow water on fine sand it walked slowly forward, and its tracks then consisted of a number of punctures on the sand in two lines. If, however, the water was very shallow or the sand very soft or inclined upward the two edges of the carapace touched the bottom, making a slight furrow at each side; and if the tail was trailed on the bottom, this made a third or central furrow. When climbing a slope, or when placed at the edge of the water, it adopted another mode of locomotion, pushing with great force with its two posterior limbs, and thus moving forward by jerks. It then made four deep marks with the toes of each hind limb, and more or less interrupted marks with the edges of the carapace and the tail. In these circumstances the marks were almost exactly like those of some forms of the Protichnites of the Potsdam sandstone. When in sufficiently deep-water and desirous to escape, it flapped its abdominal feet, and then swam or glided close to the bottom. In this case, when moving near the soft bottom, it produced a series of transverse ridges and furrows like small ripple marks, with a slight ridge in the middle, and sometimes, when the edges of the carapace touched the bottom, with lateral furrows. In this way the animals were able to swim with some ease and rapidity, and on one occasion I observed an individual, confined in a tub of water, raise itself from the bottom and swim around the tub at the surface in search of a way of escape. Lastly, the young Limuli were fond of hiding themselves by burrowing in the sand. They did this by pushing the anterior rounded end of the carapace under the sand, and then vigorously shovelling out the material from below with their feet, so that they gradually sank under the surface, and the sand flowed in upon them till they were entirely covered. If carefully removed from the hollow they had made, this was found to be ovoid or hoof shaped in form and bilobed, not unlike the curious hollows (_Rusophycus Grenvillensis_ of Billings) which I have supposed to be burrows of Trilobites. I thus found that the common King-crab could produce a considerable variety of tracks and burrows comparable with those which have been named Protichnites, Climactichnites, Bilobites, Cruziana, Rusichnites, etc.; and that the kind of markings depended partly on the differences of gait in the animal, and partly on the circumstances in which it was placed; so that different kinds of tracks do not always prove diversity in the animals producing them.