FOSSIL MOLLUSC A. 



291 



In the base of the Red Crag, the large angular flint 

 nodules are usually found thickly encrusted with 

 barnacle shells. The septarian nodules are perforated 

 with holes, bored by various boring mollusca, such as 

 PholaSy Saxicava, and we frequently find the fossil 

 shells of these borers in the holes they excavated. It 



Fig. 286. — Xucula Cobboldue 

 (Red and Norwich Crags). 



Fig. ■iZ'S,.— Valuta Lamberti 

 (Coralline and Red Crags). 



Fig. 287. — TropJton Con^ 

 trarius (Red Crag). 



is in this part of the Red Crag that the phosphatic 

 stones, or " coprolites," are usually found in greatest 

 abundance. 



A large number of mollusca, which lived in the 

 sea that covered East Suffolk during the Crag period, 



