FOSSIL MOLLUSC A. 289 



etc. This distinction of the Walton Crag has been 

 carried far enough for it to be regarded as possessing 

 some affinity with the Coralline Crag. The Fustis 

 cojttrarms is abundant there, and the bivalves are often 

 found with both shells together. The most perfect 

 fossils are found here. Great difficulty exists in 

 determining the relative ages of the Red Crag strata 

 in different localities, owing to the manner in which 

 the shell beds have been taken up and re-deposited. 

 In the Red Crag at Butley, near Orford, northern 

 forms of mollusca prevail, the commonest shell being 

 very large-sized specimens of Tellina obliqiia. 



In a pit in Tattingstone Park, about four miles 

 from Ipswich, the Red Crag may be seen overlying the 

 Coralline Crag. A thin seam of 

 pebbles marks the junction of 

 the two beds, indicating a brief 

 period between the depositions, 

 and showing that the Red and 

 Coralline Crags were not con- 

 tinuous. The places where the j,;^. .^TlZtarte cnaiu 

 sections are best exposed are on (^"'■^'i"^^ ^"^^ ^^^ Crags). 

 the slopes of the hills along the rivers Deben and 

 Orwell, in addition to the coast sections at Bawdsey 

 and Felixstowe. At the latter place is a fine section 

 thirty feet in height. As a rule, it occupies excavated 

 hollows of the Coralline Crag, wrapping round the reefs 

 of the latter, and filling up the hollows between them so 

 as to lie nearly level. Professor Prestwich divides the 



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