116 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



paper forward until I was in possession of facts which might afford 

 sufficient grounds for the conclusions I now venture to suhmit to the 

 Society. The whole question is intimately connected; yet, as the 

 geological series is divisible into distinct stages, I will take each of 

 these separately, commencing with the lowest. 



Coralline Crag. — The area of the Coralline Crag has not been 

 extended since Mr. Charlesworth first drew attention to it, giving 

 the neighbourhood of Orford as its centre, with outliers at Aldbo- 

 rough, Sutton, Eamsholt, and Tattingstone. The boundaries only are 

 better known. The extent of superficial area exposed is about eight 

 square miles. Originally the Coralline Crag may have extended 

 uninterruptedly from Aldborough to Tattingstone ; but, with the 

 exception of the low range of hills extending from Gedgrave north- 

 ward to Orford, Sudbourne, and Iken, and the small outlying masses 

 of Aldborough, Sutton, and Tattingstone, it has everywhere been 

 removed by denudation. Not only did this denudation remove the 

 Coralline Crag, but it has also removed a portion of the underlying 

 London Clay ; so that the base of the Eed Crag is in places lower 

 than that of the older Coralline Crag, round and over which it 

 wraps and passes transgressively. 



The surface of the London Clay under the Coralline Crag is also 

 uneven. In the Bullock-yard pit, on Mr. Colchester's farm at Sut- 

 ton, it is found under 4 feet of Eed and 2 of Coralline Crag, and 

 20 feet above high tide of the river Deben; but an eighth of a 

 mile to the west the London Clay is 12 feet lower, and a lower 

 zone of the Coralline Crag comes in. This and other circumstances 

 lead me to believe that at the noted old pit at Eamsholt the Coral- 

 line Crag, which there lies on the London Clay, does not belong to 

 the lowest zone, but to one some 10 to 15 feet higher. 



The well-known outlier of Sutton supplies us with a typical 

 exhibition of the Coralline Crag, the several pits which have from 

 time to time been opened there giving us the best clue to its structure 

 and dimensions, whilst at the same time the extent of denudation by 

 the Eed Crag, and the varying levels of the sea during the deposition 

 of these latter beds, are weU shown (see Plan and Sections, PI. VI.). 



It is generally known that the Coralline Crag consists of two 

 divisions — an upper one, formed chiefly of the remains of Bryozoa, 

 and a lower one of light-coloured sands, with a profusion of shells. 

 The more exact dimensions and subdivisions of these beds at Sutton, 

 Orford, Sudbourne, and Gedgrave I now purpose to give. 



The discovery of the so-called Coprolites in the Eed Crag by the 

 late Professor Henslow, in 1848, led to a great extension of crag- 

 pits. "With one exception they were all in the Eed Crag. The only 

 one in the Coralline Crag was opened by Mr. Colchester, on the 

 south side of Sutton-farm Hill (h, PL VI.). Unfortunately the pit did 

 not prove remunerative, and a year or two later it was filled up, and 

 the ground levelled ; so that it was only seen by myself and Mr. Eay 

 Lankester, as mentioned by him in a paper read before this Society. 

 The section was of much interest, as it exposed beds which belong, 

 I believe, to the lowest zone of the Coralline Crag, and showed 



