26 THE MEDALS OF CREATION. Cuap. IT. 
Obs.—The Maestricht beds are chiefly composed of fawn-coloured — 
limestones of friable texture; containing peculiar species of corals, 
shells, fishes, reptiles, &. The Chalk is generally white, but in 
some localities is of a deep red, in others of a yellow colour ; nodules, 
layers, and veins of flint occur in the upper, but are seldom present 
in the lower chalk. The Marl is an argillaceous limestone, which 
generally prevails beneath the white chalk; it sometimes contains a 
large intermixture of green or chlorite sand, and then is called 
Firestone, or Glauconite. The Galt is a stiff, blue or blackish clay, 
abounding in shells which frequently retain their pearly lustre. The 
Greensand is a triple alternation of sands and sandstones with clays; 
and beds of cherty limestone called Kentish rag. 
The WeaLpEN; 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, Zguanodon, Hyleosaurus, Pelo- 
rosaurus, Megalosaurus ; Crocodilians and Chelonians ; 
Enalosaurians ; Pterodactyles, &c. ; Fishes of fluyiatile and 
marine genera ; Insects of several orders ; fresh water mol- 
lusks 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 
repudiated the censurable practice of many modern systematists, of 
changing established names of strata and fossils, without any just 
eause. The British geologist will smile to see the Wealden Formation 
—so eminently distinguished in England and Germany by its extent, 
thickness, and remarkable fauna and flora,—ranked as a subordinate 
member of the “ Formation n€éocomien,” of France. 
