SYNOPSIS OF THE BRITISH STRATA. 5 | 
deposits that intervene between the Triassic above, and the Carboni- 
ferous below; and it is believed that this formation contains but 
one type of animal and vegetable life. 
THE CARBONIFEROUS, or Coat Formation. (Wond. pp. 660 
—748). Sandstones, grits, shales, layers of ironstone, and 
clay, with immense beds of coal; fresh-water limestones 
sparingly ; marine limestones abundantly. 
Subdivisions :— 
1. The Coal Measwres.-—Sandstones, shales, and grits, with nume- 
rous beds and seams of Coal; ironstone nodules. Land 
plants in profusion. Intercalations of bands of limestone 
with fresh-water bivalves and crustaceans in some districts ; 
and with marine shells in others. 
2. Millstone Grit. —Sandstones, shales, and quartzose conglo- 
merates and grit, (provincially, Millstone-grit) : with shales 
and thin seams of coal, and plants of the coal measures in 
some localities. The conglomerates and grits have evidently 
resulted from the destruction of granitic rocks. 
3. Carboniferous, or Mountain Limestone.—A series, nearly 1,000 
feet in thickness, of limestones and flagstones, abounding in 
crinoideans, corals, and marine shells and crustaceans ; 
with layers and nodules of chert. Ores of lead, zinc, copper, 
barytes; fluor spar, &c. lLimestones, with innumerable 
shells of the genera Productus, Spirifer, Goniatites, Ortho- 
cera, Bellerophon, &c. Several varieties of black, bluish 
grey, and variegated marbles. Coal occurs in the mountain 
limestone of some parts of Russia. 
Obs. — The strata comprised in the carboniferous (coal-bearing) 
system, consist of sandstones more or less felspathic, and of dark 
bituminous shales with innumerable ferns, and other vascular 
cryptogamie, and conifer, &c. The uppermost group is composed 
of numerous alternations of coal, clay, shale, ironstone, and sand- 
stone; the middle, of sandstones, shales, clays, and quartzose conglo- 
merates, generally of a dull red colour; and the lowermost, of crys- 
talline limestones with occasional layers of chert, abounding in 
marine shells, corals, crinoidea, and other exuvie. These lower lime- 
stones are the principal repositories of the lead ores of Derbyshire. 
Tue Dervonran or OLD Rep Formation. (Wond. pp. 204 
and 751). Conglomerates, quartzose grits, sandstones, marls, 
