2 LOWER OOLITIC ROCKS OF ENGLAND : 
Buckland, and others, the names Inferior and Great Oolite, 
Coralline or Oxford Oolite, and Portland Oolite, came to be applied 
to different beds of limestone in the Oolitic Series. 
The general sequence that has been established in the Jurassic 
rocks of this country, has been mentioned in the previous volume 
on the Lias. In lhat formation the main divisions can be followed 
across the country from Dorsetshire to Yorkshire ; while in regard 
to the Oolites distinct stratigraphical divisions are necessary in 
different parts of the area, owing to the inconstant character of 
some of the subdivisions, and more especially those of a calcareous 
and arenaceous nature. The limestones characterized by oolitic 
structure are as a rule conspicuously current-bedded, and they, 
together with the sandy sediments, were evidently deposited in 
comparatively shallow water ; while the clays, as a rule, indicate 
the sediments of deeper water that were further removed from 
the land. 
We have thus to deal with a series that exhibits marked 
changes in the thickness and character of its numerous divisions ; 
for the total thickness varies from about 1,500 to nearly 3,000 
feet. Evidences of terrestrial conditions are afforded in the 
Northampton Sand and in the Purbeck Beds ; but the only direct 
evidence of an old land-area (probably of an island) is met with 
in the Mendip Hills, where conglomeratic beds of Inferior Oolite 
rest on the Carboniferous Limestone. Indirect evidence is 
otherwise afforded of the nearness of land, whether of islets or 
portions of a continent it is difficult to say. This evidence is 
gathered partly from the pebbly character of the Lower Calcareous 
Grit and Portlandian Beds, and partly from the estuarine nature of 
other strata, a character which becomes developed in portions of 
the Lovrer Oolitic Series as we proceed from the south-west of 
England in a north-easterly direction into Yorkshire. The 
evidence of the proximity of land and of esttinrine conditions, is 
derived from the occurrence of much lignite and of certain Mollusca : 
while the occurrence, as at Stoneefield, of plants and terrestrial 
animals, is indicative perhaps of an island. In the Northampton 
Sand we. have layers penetrated by rootlets ; and in the highest of 
the Jurassic Rocks, the Purbeck Beds, we find remains of the 
growth in situ of Cycads and Conifers, as well as beds of distinctly 
freshwater origin. It should be noted, however, that the presence 
of lignite, or even of leaves, seeds, and fruits, affords no indication 
of the depth of water in which beds may have been deposited, 
as such remains have been dredged from a depth of over 1,500 
fathoms off the West Indies.* 
The Oolitic Series., so far as our area is concerned, is broken 
only by the local absence of one or more of its members, an 
absence that may in some cases be attributed to contemporaneous* 
erosion and in others to cessation of sediment. There are no 
facts to tell of any great and wide-spread discordance such as 
would be produced by considerable upheaval and erosion. 
* A. Agassiz, Nature, January 21, 1892, p. 281. 
