On the top of the “Upper Trias,” or “Keuper” formation, we have the Lias, which succeeds the Rhætic beds, and in this we find many rich traces of reptiles and birds which come now before us in the rising scale of creation. In the seas of this period we have numerous crustacea, the nautilus and the cuttle-fish. The Saurians now come before our retrospective vision. It is the “Reptile Age” in all its development, and the huge labyrinthodon, the iguanodon, pterodactyle, and ichthyosaurus testify to the magnitude of the fauna of the period. The first mammal specimen, a marsupial, has been traced back to this time; and the tropical temperature was favourable for luxuriant vegetation, pines, and palms.
In the swamps or shallow waters the great reptiles disported themselves, and seized their prey, the water-fowl, which now appeared in numbers, and of enormous size. Nor were insects absent. Numbers of remains have been discovered; beetles, dragon-flies, grasshoppers, etc., in multitudes yield us information, while the marine fossils, star-fish, mollusca, and various fishes, are of frequent occurrence. Animal and vegetable life during this period must have been very rich and varied—literally leaving “footprints in the sands of time.”
Fig. 673.—Pterodactylus longirostris.
The “Blue Lias” is a term familiar to every reader. It is a kind of limestone mixed with clay, of a blue colour, and upon this we find the Oolitic, or Oolite System—so called because it somewhat resembles the roe of a fish. The Lias clays are used for bricks, and Whitby “jet” is also obtained from the Upper Lias. Jet is really a lignite, or wood in the process of transmutation. In this Lias formation, besides the numerous fossil remains already mentioned, we find the “snakestones” (ammonites), the stone-lily, and belemnites, with many nautili and shells.
Fig. 674.—Ichthyosaurus.
The Oolite, or Jurassic, underlies the chalk, and overlies the Trias formation. The term “Jurassic” originates from the Jura range, which is almost entirely composed of Oolitic strata. These strata are greatly distorted by pressure, and when we reach Switzerland and the familiar Alps, we find gneiss, crystalline, limestones, and schists, into which the Oolite has been metamorphosed. The Oolite is divided into Upper, Middle, and Lower, consisting of the following:—
| Upper Oolite | ⌈Pembroke Beds. ⎢Portland Beds. ⌊Kimmeridge Clay. |
| Middle Oolite | ⌈Calcareous Grit. ⎢Coral Rag. ⌊Oxford Clay. |
| Lower Oolite | ⌈“Cornbrash”—Forest Marble. ⎢Stansfield Slate. ⎢Bath Oolite. ⎢Fuller’s Earth. ⌊Inferior Oolite. |
