CLASSIFICATION OF THE OOLITE. 
321 
CHAPTER XIX. 
JUEASSIC GEOUP.-PIJEBECK BEDS AND OOLITE. 
The Purbeck Beds a Member of the Jurassic Group.—Subdivisions of that 
Group.—Physical Geography of the Oolite in England and France.—Up¬ 
per Oolite.—Purbeck Beds.—New Genera of fossil Mammalia in the 
Middle Purbeck of Dorsetshire.—Dirt-bed or ancient Soil.—Fossils of 
the Purbeck Beds.—Portland Stone and Fossils.—Kimmeridge Clay.— 
Lithographic Stone of Solenhofen.—Arch^opteryx.—Middle Oolite.—Cor¬ 
al Bag.—Nerinsea Limestone.—Oxford Clay, Ammonites and Belemnites. 
—Kelloway Rock.—Lower, or Bath, Oolite.—Great Plants of the Oolite. 
—Oolite and Bradford Clay.—Stonesfield Slate.—Fossil Mammalia.— 
Fuller’s Earth.—Inferior Oolite and Fossils.—Northamptonshire Slates.— 
Yorkshire Oolitic Coal-field.—Brora Coal.—Palaeontological Relations of 
the several Subdivisions of the Oolitic group. 
Classification of the Oolite. —Immediately below the Has¬ 
tings Sands we find in Dorsetshire another remarkable fresh¬ 
water formation, called the PurhecJc^ because it was first stud¬ 
ied in the sea-cliffs of the peninsula of Purbeck in that county. 
These beds are for the most part of fresh-water origin, but 
the organic remains of some few intercalated beds are marine, 
and show that the Purbeck series has a closer affinity to the 
Oolitic group, of which it may be considered as the newest 
or uppermost member. 
In England generally, and in the greater part of Europe, 
both the Wealden and Purbeck beds are wanting, and the 
marine cretaceous group is followed immediately, in the de¬ 
scending order, by another series called the Jurassic. In this 
term, the formations commonly designated as “ the Oolite 
and Lias ” are included, both being found in the Jura Mount¬ 
ains. The Oolite was so named because in the countries 
where it was first examined the limestones belonging to it 
had an Oolitic structure (see p. 37). These rocks "occupy in 
England a zone nearly thirty miles in average breadth, which 
extends across the island, from Yorkshire in the north-east, 
to Dorsetshire in the south-west. Their mineral characters 
are not uniform throughout this region; but the following 
are the names of the principal subdivisions observed in the 
central and south-eastern parts of England. 
OOLITE. 
(a. Purbeck beds. 
Upper . . . 6. Portland stone and sand. 
(c. Kimmeridge clay. 
14* 
