PRESTWICn— CRAG-BEDS OF SXJrrOLK AND SORFOLK. 341 



water of the river Deben, which can vary but little from that of 

 the sea on the adjacent coast, from which this part of the river is 

 only five miles distant. The upper cliflf (o', fig. 21), which is not 

 well exj)osed, is about 12 feet high, and must formerly have been 

 higher, as blocks of the consolidated bed of Bryozoa capping the 

 hill higher up are found at its base. They may have toppled over 

 the brow of the old clifi', or been detached and carried a short dis- 

 tance by ice-action. At all events it is evident, from the way in 

 which the blocks of CoraUine Crag, 1, 2 in fig. 22, have impressed 

 and squeezed up the lower layers of Eed Crag in which they rest, 

 that they fell on the spot where they now lie whilst the Red Crag 

 was in course of formation, and that the upper part of the Red 

 Crag was deposited subsequently to the fall of the blocks. The 

 larger of these angular blocks of CoraUine Crag may weigh more 

 than a ton. In addition to these large blocks there are many 

 smaller ones — some perforated by Annelids, and others covered with 

 Balani (B. crenatus). Together with these are a number of pebbles 

 of flint, some coprolites, and some large masses of angular and un- 

 worn flints. Interspersed with this coarse shingle are an abundance 

 of shells (chiefly Mytilns edulis) with both valves. The Pholas- 

 perforations commence at the top of the upper shore, and pass over 

 the brow of the lower cliff, o. A few feet back from the face of the 

 section the Coralline Crag rises to the surface of the ground. 



To ascertain the position of the lower shore-line, I had a trench 

 dug at the bottom of the pit and below the level of the upper shore, 

 s' (fig. 21). I found the Red Crag to extend about 4 feet deeper, 

 and at its base a shingle composed of phosphatic nodules and of 

 large flints, over which there was a thin bed of Mytilus edulis, almost 

 all with the two valves, and apparently in the spot where they lived. 

 This shore-line is '22 feet above high- water mark. Its character 

 is better seen in a pit (G) situated on the other side of the old reef, 

 350 yards west of the pitD (see PI. VI.). The details of this pit are 

 given in fig. 23. On the upper shore in pit D I found only two large 

 blocks of Coralline Crag ; but on this lower shore the blocks were many, 

 whilst numerous smaller fragments were dispersed throughout the 

 section, showing the removal of the adjacent CoraUine Crag to have 

 been more active at the commencement of than further on in the 

 Red Crag period. Flints and phosphatic nodules are dispersed here 

 and there. Apparently this pit is at a rather greater distance than 

 pit D from the old submerged reef. 



The occurrence of these transported blocks of CoraUine Crag is 

 pecuUar to these pits. There are, however, few other pits so near as 

 these to the CoraUine Crag ; and the upper bed of the CoraUine Crag 

 is here also more compact than elsewhere. But although the debris 

 of the Coralline Crag is nowhere else so abundant, it may never- 

 theless be detected in most of the pits of the Red Crag in this dis- 

 trict. SmaU pieces and fragments of the harder seams of the Coral- 

 line Crag, together with its Corals and Bryozoa, are extremely common 

 in the Red Crag at Waldringfield, one mile direct from Sutton. I have 

 also found worn fragments of the Coralline Crag in the Red Crag at 



vol. XXVir. PART I. 2 b 



