Dr. Buckland states that Miss Potts, of Chester, had sent to him a flagstone from a coalshaft at Mostyn, bearing impressions which he supposed to be the trackway of some fish crawling along the bottom by means of the anterior rays of its pectoral fins. There were no indications of feet, but only scratches, symmetrically disposed on each side of a space that may have been covered by the body of the fish whilst making progress, by pressing its fin-bones on the bottom. As yet, no footsteps of reptiles, or of any animals more highly organized than fishes, have been found in strata older than those which belong to the new red sandstone. The abundant remains of fossil fishes, armed with strong bony spines, and of other fishes allied to the gurnard, in strata of the carboniferous and old red sandstone series, would lead us to expect the frequent occurrence of impressions made by their locomotive organs on the bottoms of the ancient waters in which they lived. Dr. Buckland proposed to designate these petrified traces or trackways of ancient fishes by the term of fish-tracks. Crabs and Lobsters are strange creatures: strange in their configurations; strange in the transmutations which they exhibit from the egg to maturity; strange in the process they undergo of casting off, not only their shell, but the covering of their eyes, of their long horns, and even the lining of their tooth-furnished stomach; strange, also, are they in their manners and habits. Many a reader, in wandering along the sea-shore, may have disturbed little colonies of Crabs quietly nestling in fancied security amidst banks of slimy sea-weed; and in the nooks and recesses of the coast, the shallows, and strips of land left dry at ebb-tide, may be seen numbers of little, or perchance large, Crabs, some concealed in snug lurking-places, others tripping, with a quick _side-long_ movement, over the beach, alarmed by the advance of an unwelcome intruder. Some are exclusively tenants of the water, have feet formed like paddles for swimming, and never venture on land; others seem to love the air and sunshine, and enjoy an excursion, not without hopes of finding an acceptable repast, over the oozy sands; some, equally fond of the shore and shallow water, appropriate to themselves the shells of periwinkles, whelks, &c., and there live in a sort of castle, which they drag about with them on their excursions, changing it for a larger as they increase in measure of growth. They vary in size from microscopic animalcules to the gigantic King Crab:[21] to the former, the luminosity of the ocean, or of the foam before the prows of vessels, is, to a great extent, attributable, each minute creature glowing with phosphoric light.