CHAPTER XIV.

Second Period of the Mesozoic Age. - Wealden and Oolite Formations - Period of Enormous Land Reptiles - Mammalian Animals first introduced.

NEXT in order above the Lias, we find the Oolite. The rocks of this formation embrace clays, shales, limestones, and sandstones. It is largely developed in England and in the Jura mountains. It derives its name from the round egg-like nodules found in many of the limestones of the formation. Oolite limestone is found in abundance in other groups, as, for example, in the Carboniferous, but the distinctive name Oolite has been appropriated to this one.

In our country there is a small deposit near Richmond, Virginia, which, from its fossils, etc., has been pronounced Oolite by very competent judges. It contains coal.

Fossils.-The Flora of the Oolite was rich and beautiful. It consisted of cycads, conifers, ferns, and palms.

The cycads were very abundant. Some of them were short, stumpy, cylindrical, scaly stems, with large, fern-like looking leaves. Others were large, having trunks thirty feet long.

Lignites and coal are found in the Oolite beds of Europe; but the largest coal-beds of this formation are at Richmond, Virginia.

The Fauna.-All the divisions of the animal kingdom were represented here.

Of the Radiates, we find corals in reefs; as the Coral Rag of England, acalephs, crinoids, and starfishes. Among the corals we find the Caryophillia annularis and the Astrea; and among the crinoids. was the Pear Encrinite.

The Molluscs were very abundant, and they were exceedingly beautiful.

Ammonites and Belemnites appeared in all their beauty. They were the gems of the ocean.

Articulates existed in the form of crustaceans and insects. Their remains are found in clay. The entire exterior of a lobster-like animal is found, and the remains of insects very much like the dragonfly have been preserved, even to the nerves of the wings.

Vertebrates.-Reptiles and fishes shared the Oolitic ocean with the other animals of which we have

spoken.

Of the reptiles, the most prominent were the Ichthyosaurus, Plesiosaurus, and Megalosaurus. The most remarkable was the Pterodactyle.

This creature had the wings of a bat, the head of a crocodile, and the body of a mammal. It could walk, fly, or swim, according to inclination or emergency.

The Pterodactyle.

The fishes of the Oolite are principally ganoids. The mammals appear to have resembled the opos

sum and kangaroo. Several specimens of the lower jaws of such quadrupeds have been found. Two distinct genera have been defined, to which the names Amphitherium and Phascolotherium have been given.

The Wealden range is interesting, from the fact that the deposits are fresh-water.

The relative order of the beds, as reported by English geologists, is as follows:

1. Weald Clay, with some Limestone and Sand. Fresh-water Shells. 2. Hastings Sand- Sandstone, Conglomerate, and Lignite. Freshwater Shells.

3. Purbeck Strata. Limestone and Clay, alternating, resting upon

Oolite.

The whole amounting to 1000 feet in thickness. It is found in Great Britain, France, and Germany, but does not appear in the United States.

It takes its name from the old word wealds, which means woods; being largely developed, and first noticed in the forests of Kent and Sussex.

tions of the Lias, Oolite, Wealden, and Chalk.