the various members of the animal and vegetable kingdoms particular geological periods; for fossilised remains of animals and vegetables have been unearthed in the different layers of the stratified rocks, conclusively proving their existence on the earth at those periods. In the Plutonic or unstratified rock-formation period there was, of course, no life upon the earth, the conditions necessary for such development not being present; but in the very earliest of the stratified formations we find evidence of the dawn of marine life, both vegetable and animal. Geologists have divided the stratified rock into three chief divisions, the Palæozoic (ancient life), or Primary; the Mesozoic (middle life), or Secondary; and the Kainozoic (latest life), or Tertiary. Each of these, again, has been subdivided into smaller sections, according to the particular kind of deposit met with, the particular places where the best examples are to be found, or the particular life-forms existing. The Primary, the depth of which is unknown, is subdivided into seven periods—viz.:— Laurentian, consisting of highly metamorphosed (that is, changed in appearance from the original stratified rock character, owing to its proximity to the molten Plutonic rock) limestone, containing fossil remains of the Foraminifera, some of the first living organisms. Huronian, consisting of less highly metamorphosed sandstone, limestone, etc., and containing fossil remains of lowly-organised molluscs (soft-bodied organisms). Cambrian, consisting of slates, sandstones, and conglomerates, and containing fossil remains of sponges, sea-weeds, star-fishes, sea-lilies, lowly shell-fish, marine worms, and the first land plants. Silurian, consisting of slates, limestones, etc., and containing fossil remains of corals, chambered spiral shell-fish, crabs, sea-worms, and bony plates and scales of a low form of fish. Devonian, consisting of old red sandstone, shales, and coralline limestone, and containing fossil land plants, fishes, belonging to shark, ray, and sturgeon families, and first fossil insect. Carboniferous, consisting of mountain limestone, coal, sandstone, ironstone, clays, etc., and containing fossil scorpions, beetles, and amphibians. Permian, consisting of new red sandstone, marls, magnesian limestones, etc., and containing fossils of true reptiles. The Secondary division is subdivided into three periods, viz.:— Triassic, consisting of sandstone, limestone, and clays, and containing fossils of gigantic reptiles and first mammals (small marsupials). Jurassic, or Oölitic, consisting of limestones, coral rags, clays, and marls, and containing fossils of bird-reptiles and several species of marsupials. Cretaceous, consisting of clays, sands, soft limestone, and lignites, and containing fossils of new bird-reptiles. The Tertiary division is subdivided into four periods—viz.:—