1849.] PRESTWICH ON THE CRAG AT CHILLESFORD. 347 



Fig. 1. 



Section at Iken Brick-field. 



.-T^TTTq: :tT.,-;.?.-.".-^ ,;• : 2::i^^^^ ^^^^^ ^j=- a «. Flint gravel, 1 to 3 feet. 



f^ I^^^^S I, b. Laminated grey clays and sands with indistinct im- 



•5: ' • -^^^— WT -. pressions of shells, 10 feet. 



—i!-, M . «- 'j-^,u<;j^^^ y:^z_-^- -^-,rr^^ ~— r ^- YcUow sands, 4 feet. 



''^-s =-=-^^^^=:^^^ ^ . s,,,=:..^2^j r7f!r. c c- Light bright yellow coralline crag full of the ordinary 

 ^^^^^^^^^^^^^^^^ fossils, chiefly corals, +30 feet. 



compact calcareous coralline crag is slightly uneven and waterworn. 

 The sands which repose upon it are more siliceous, and exhibit 

 at their base occasional patches of rounded and angular gravel, in 

 which, we were informed, blocks of hard stone of considerable size 

 were sometimes found. Both in mineral structure and in organic 

 remains there is evidence of a change of conditions. Of all the 

 abounding corals of the coralline crag, none exist in this upper bed. 

 Instead of the thick mass of peculiar zoophytes and mollusks of the 

 former, we find a new and scanty fauna imbedded in a very different 

 manner. In the crag both coralline and red, but more especially in 

 the latter, the organic remains are accumulated generally in great 

 confusion ; the bivalve shells rarely have their two valves together, 

 are often broken, and oftener still form whole beds of their commi- 

 nuted fragments. Yet more rarely, apparently, do the remains occur 

 in the position in which the animal lived. But in these overlying 

 clays and sands such appears to be the usual condition, and not the 

 exception. The bivalves which we found very constantly exhibited 

 both the valves in contact, and often in the position in which the 

 animal lived. We could, however, at this pit only note their forms ; 

 the shell had in all cases been removed, and merely a soft cast of clay 

 or sand was left behind. 



We thence proceeded southward to Sudbourn, examining on our 

 way several pits which exhibited no traces of the beds " 6" and "c," 

 but afforded many very good and interesting examples of the super- 

 position of the red crag on the coralline crag. Neither did we ob- 

 serve the newer beds in the neighbourhood of Orford or of Sudbourn 

 Park. Taking thence a westerly direction to Chillesford, three miles 

 by road north-west from Orford, upon arriving at the entrance of the 

 village we turned off to the brick-kiln, which stands on the hill a 

 quarter of a mile north of the main road, and there found another 

 outcrop of fossiliferous clays and sands, forming partly the surface of 

 the hill-top, and consisting of twelve feet of yellow and grey sandy 

 clays more or less laminated, with numerous indistinct casts and im- 

 pressions of shells, overlying five feet of yellow sand, with a few shells 

 scattered in its lower part. The crag beds did not come to the surface 

 in this pit ; but in a well about thirty feet deep, sunk in the middle 

 of the pit and through the yellow sands, the workmen informed us 

 that the common red crag of the country was reached at a depth of 



VOL. V. PART I. 2 B 



