The Wealden; a formation, whose fluviatile character was first observed and established by the researches of the author (Wond. p. 360). A series of clays, sands, sandstones and limestones, with layers of lignite, and extensive coal-fields; characterized by the remains of several peculiar terrestrial reptiles, namely, Iguanodon, Hylæosaurus, Pelorosaurus, Megalosaurus; Crocodilians and Chelonians; Enaliosaurians; Pterodactyles, &c.; Fishes of fluviatile and marine genera; Insects of several orders; fresh-water mollusks and crustaceans; conifers, cycads, ferns, &c.

Subdivisions:—

1.Weald-clay, with Sussex or Petworth marbles.
2.Tilgate-grit, and Hastings sands.
3.Ashburnham clays, shales, and grey limestones.
4.Purbeck beds; argillaceous and calcareous shales, and fresh-water limestones and marbles. Petrified forest, and layers of vegetable earth; with Cycads and Conifers.

Obs.—Clays and limestones, almost wholly composed of fresh-water snail-shells, and minute crustaceans, generally occupy the uppermost place in the series in Sussex; sands and sandstones, with shales, and lignite, prevail in the middle; while in the lowermost, argillaceous beds, with shelly marbles or limestones, again appear; and, buried beneath the whole, is a petrified pine-forest, with the trees still erect, and the vegetable mould undisturbed! The upper clay beds and marbles form the deep valleys or Wealds of Kent and Sussex, and the middle series constitutes the Forest-Ridge. The Purbeck strata are obscurely seen in some of the deepest valleys of eastern Sussex; they emerge on the Dorsetshire coast, form the Island or Peninsula whose name they bear, and surmount the northern brow of the Isle of Portland. On the southern coast of the Isle of Wight, the Wealden beds emerge from beneath the Greensand strata between Atherfield and Compton Bay on the western limit, and in Sandown Bay on the eastern; and their characteristic fossils are continually being washed up on the sea-shore.

The Jurassic or Oolitic Formation. (Wond. pp. 202, and 491). A marine formation of great extent and thickness, consisting of strata of limestone and clay, which abound in extinct species and genera of marine shells, Corals, Insects, Fishes, and terrestrial and marine Reptiles. Land plants of many peculiar types, and the remains of two genera of Mammalia.

Subdivisions:—

Upper Oolite of Portland, Wilts, Bucks, Berks, &c.

1.Portland Oolite. Limestone of an oolitic structure, abounding in ammonites, trigoniæ, &c. and other marine exuviæ. Green and ferruginous sands—layers of chert.
2.Kimmeridge clay. Blue clay, with septaria, and bands of sandy concretions—marine shells and other organic remains—ostrea deltoidea. Beds of lignite.

Middle Oolite of Oxford, Bucks, Yorkshire, &c.

1.Coral oolite, or Coral rag. Limestone composed of corals, with shells and echinites.
2.Oxford clay; with septaria and numerous fossils. Beds of calcareous grit, called Kelloway-rock swarming with organic remains.