292 OUR COMMON BRITISH FOSSILS. 



are now living further south, in the Atlantic or the 

 Mediterranean, having been driven from these areas 

 by the increasing cold, which here reached its maxi- 

 mum during the Glacial epoch. 



The best places to obtain Red Crag fossils are pits 

 at Wherstead, Tattingstone, Bentley, Foxhall, Boyton, 

 places near Woodbridge, Bucklesham, Walton, the 

 Felixstowe cliffs, Bawdsey, Chillesford, Sudbourne, 

 Butley, Aldborough, etc. 



The Norwich Crag was formerly called the 

 " Mammaliferous crag." But it has been shown that 

 the mammalian remains are older than the shells 

 associated with them. In Suffolk this crag occurs at 

 Thorpe, near Aldborough, at Bulcamp, and Chilles- 

 ford. Sir Charles Lyell gave to it the name of 

 " Fluvio-marine Crag," on account of the large per- 

 centage of land, fresh-water, and brackish-water shells 

 it contains. It is usually regarded as nearly syn- 

 chronous with the Red Crag, and as a fluvio-marine 

 extension of the latter. The shells of the Norwich 

 Crag are remarkable for their littoral, or shallow water 

 character. The most abundant fossils are Littorina 

 littorea^ Purpura lapillus, Cardium edule^ Mytilus 

 edtdisy Cerithium tricinctum, Turritella communis^ 

 Natica monilifera, Tellina prcstenuis, T. obliqiia, etc. 

 At the base of the railway cutting, about a mile from 

 Aldborough station, we have found undoubtedly Red 

 Crag shells associated with others we regard as equally 

 undoubted Norwich Crag forms, indicating that here 



