The body of the trilobite was composed of numerous rings or segments, and each of these rings was divided into three lobes, from which it receives its name, tri-lobe-ite, or three-lobed animal. All the rings of the body were so joined that the trilobite could roll itself into a ball, doubling its tail forward under its head, and so bringing all parts of its body under the protection of the horny shield. Have you never, in turning over earth or breaking a decayed stump, found numbers of small, oval, soft, gray, ridged creatures called slaters or wood-lice? Have you noticed how as soon as they are disturbed they roll themselves into an apparently lifeless coil? In this fashion some of the trilobites were like the wood-louse. For a long time it was supposed that the trilobite had no legs; but at last it was found that they had a number of small, thin-jointed legs, like those of a young spider-crab. Thus we see that in its head-shield and eye-placement, the trilobite was like a horseshoe crab, or limulus, which is no doubt its near relation; in general form it was like a young isopod; in its method of rolling itself up for rest or safety, it was like a wood-louse; in its long, thin legs it was like a small spider-crab. During one earth-building age, the trilobite was the chief representative of the crabs, and many hundred species of trilobites have been discovered. We find that their patterns varied much in the days when they were the leading order of the earth. The track of the trilobite in the mud in which it lived was peculiar, and has gained the name of “ladder footprints.” These footprints have been preserved in the hardened mud, as have rain-drop prints and birds’ tracks. The slim, sharp-toed feet of the trilobite made little rows of dots, and on each side of these was a deep groove, the rows of dots looking like the rounds, and the grooves like the sides of a ladder. This double groove was caused by the dragging edges of the shield or head-plate, and the ladder footprint is much like the track of a king-crab. Floating above the primordial mud, in good fellowship no doubt with the trilobite, was the brachiopod, or “arm-footed” creature. This name was given because of numerous slim finger-like appendages, such as the barnacle uses for its fishing apparatus.[35] The bra-chi-o-pod was partly like the crustaceans and partly like the mollusks, while some learned men have concluded it to be closely related to worms and star-fish! In fact these ancient families of animals had many points in common. Perhaps the ancient lamp shells were the representatives of the brachiopods when all these first families of the world lived together in the Cambrian seas.