Page:A Treatise on Geology, volume 1.djvu/238

 222 which has been ascribed to the deposition of formations, from considerations founded merely on the state of conservation of organic remains.

Organic Remains.—The numerous remains of plants, zoophyta, mollusca, articulosa, and vertebral animals, belonging to the oolitic system, have long been celebrated and represented in many works of merit in England and Germany. Some general considerations arise from a contemplation of them, which deserve attention. The following estimate of the numbers of specific forms in the whole system (exclusive of the wealden formations), drawn up by the author, is at this time undoubtedly below the truth. (Encycl. Metrop. p. 653.)

In the wealden formation, are no zoophyta, no cephalopoda—various land plants—some fresh-water bivalves and univalves—a few estuary shells—cyprides, lepidotus, and other fishes—iguanodon, hylsæosaurus plesiosaurus, &c., with various chelonida, both of fresh and salt water.

The most characteristic of the plants are the group of cycadeæ, of which stems in the isle of Portland, and leaves and fruits in Yorkshire, show considerable analogy to the existing forms of the tribe, at the Cape of Good Hope, and in India and Australia. Compared with