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Suffolk as the Crag, and divided scientifically into the Coralline Crag 
and the Red Crag, were the only British representatives of the older 
Pliocene period. 
When they occurred in the same district, the Coralline Crag lay 
beneath the Red Crag, and where the former was wanting the Red 
Crag rested upon the London Clay, which, being one of the beds of the 
Lower Eocene, was, of course, of much greater antiquity than the Crag, 
The White and Red Crags belonged to different periods, and there was 
sufficient evidence of the fact that the temperature of the sea was 
higher during the deposition of the Coralline Crag than it had become 
when the Red Crag was deposited, many of the species of shells and 
Polyzoa found in the former, which had not become extinct, existing 
now only in more southern seas. In the same way it was observed 
that the living species represented in the Red Crag, but not in the 
Coralline, had a more northern character, many of them still inhabit- 
ing our own coasts. These and other facts, together with the further 
evidence furnished by the Norwich Crag, were of great interest, as 
showing the gradual coming on of a more severe climate, which 
resulted in the Glacial Epoch extending all over the north of Europe 
and America. 
The Coralline Crag was composed chiefly of soft marly sands, 
generally calcareous, often a mass of comminuted shells, passing 
occasionally into a soft building stone, which was quarried in the 
neighbourhood of Orford. In some places the softer mass was divided 
by thin bands of hard limestone. It was usually about twenty feet 
thick, though in some places it was said to reach fifty feet. But one 
of the most remarkable things about it, as one of the vestiges of 
creation, was its limited extent, the Coralline Crag being confined toa 
strip of country twenty miles long by three or four miles wide, between 
the river Alde and the river Stour. 
The Red Crag occurred, with breaks, from Aldborough to Walton- 
on-the-Naze, and extended inland from some five to fifteen miles. It 
was generally from ten to twenty feet in thickness, though it 
occasionally reached forty feet, including beds of rough red sand at the 
top, without shells. It would be in vain (said Mr. Scott) to attempt 
any description of the shells of the Crag. They were well represented 
on the table, and were described and figured in Mr. Searles Wood’s 
admirable ‘‘ Monograph of the Crag Mollusca,” in the Society’s 
library. The important fact was, he thought, established by Mr. 
F 
