The oolite occupies, in England, a zone nearly thirty miles in breadth, extending across the country from Yorkshire to Dorsetshire. In 'Scotland, patches of lies and Oxford clay occur in the islands of Mull and Skye, and on the western shores of the mainland, and beds belonging to the lower oolite are found at Brora, on the east coast of Sutherland, which contain an impure coal. The only colite rocks in Ireland are a few isolated patches in Antrim, which abound with the fossils of the lower has. On the con tinent, rocks of this age occur in Germany and France, but they have been most exten sively studied in the Jura mountains, which, though having a height of 6,C00 ft. are entirely composed of oolite and cretaceous rocks. The strata are greatly- bent and con torted, and as they approach the Swiss Alps, the great mass of which is also formed of oolite, they become completely metamorphosed into clay slates, mica schists, gneiss, and crystalline limestones. Beds of oolite have been noticed in Cutch, in India. In Austra lia similar beds occur on the western coast, and probably some of the coal-beds of New South Wales, Victoria, and Tasmania belong to the wine. In both North and South America, fossils, apparently of oolitic age, have been found; but these deposits requila to be more exactly examined.
The oolite is remarkable for the abundance of its fossils, and is in this respect in striking contrast to the immediately preceding Triassic and Permian periods. The several fresh-water deposits, and the ancient vegetable surfaces, contain the remains of a considerable number of plants. Ferns still abound, and with them are associated species that are evidently related to the living genera cupressus, araucaria, and gamut.
Corals abound in several of the beds. The brachiopods are the only division of the mollusca that is not largely represented. The conchifers and gasteropods show a great number and variety of new genera, which are nearer the forms of the present day than those that preceded them. But the remarkable feature of molluscan life is the enormous development of the cephalopods. Whole beds are almost entirely made up of their shells, No less than 600 species of ammonites have been described, chiefly from the rocks of this period, and the belemnites were also very numerous. The crinoids have become scarce, but are replaced by star-fishea and sea-urchins. The fresh-water beds contain the remains of many insect forms. The lieterocereal-tailed fish give way to the more modern homocercals, and the true sharks and rays make their appearance, though the old cestracionts are still represented by some survivers. The characteristic feature of the oolitic period was its reptiles. The land, the sea, and the air had each their fitting inhabitants of this class. The various species of pterodactyles, some not larger than the bat, others surpassing, in the stretch of their membranous "sting," the size of the largest living bird, were the terrors of the air; while their allies, the monster ichthyosaurs and plesiosaurs, held the mastery of the waters; and the huge megalosaurs, some not less than 30 ft. in length, trod the earth. The few mammalian remains hitherto found have a special interest from their antiquity, being the first evidence of this high order of animals on the globe. They belong, apparently. to marsupial animals; one species is, however, supposed by Owen to have been a hoofed and herbivorous placental mammal.