468 



PLIOCENE. 



localities in succession would be convinced that the Chillesford Clay was a well- 

 marked horizon in Norfolk. But if he endeavoured to trace out these clays on the 

 ground, noticing the intermediate sections, and the behaviour of the clays them- 

 selves, he would become convinced that, while such laminated clays are 

 characleristic of the Pliocene beds of Norfolk, they are not confined to one 

 horizon, they were not all deposited at one particular time, and their absence 

 is not necessarily the result of denudation. The sections at Coltishall and 

 Hartford Bridges demonstrate that these clays are intimately connected by false- 

 bedding with the pebbly gravels (Bure Valley Beds) that often overlie them, and 

 that they pass occasionally by interbedding in their horizontal extension into sand 

 and gravel. In some sections we find two or more bands of clay, any one of 



Fig. So. — Chalk-pit at Whitlingham, near Norwich. 



4. Pebbly grr.ivel and sand, with seam of shells. 



3. Laminated clay (impersistent), and shelly seam. 



2. False-bedded sand and gravel, with shells. 



1. Stone bed. 



A. Chalk with flints. 



Norwich 



Crag 



Series. 



15 to 20 feet. 



which might on lithological grounds be termed the Chillesford Clay. Hence 

 but little dependence can be placed on the particular correlation of beds by means 

 of laminated clay-bands, for similar beds occur also in the Cromer Forest Bed 

 Series : indeed, the name Laminated .Series has been applied by Mr. Gunn to the 

 Pliocene strata of Norfolk. 



When we come to study the shells in the several beds of Crag, even those 

 acknowledged to be on the same horizon, we find that they vary not only in the 

 abundance of particular forms, but also in the number of different species, indi- 

 cating perhaps slightly varying depths of water or diversities in the sea-bed, that 

 influenced their distribution. At Brundall Station jVuciila Cobboldiic is very 

 abundant. At Brundall Church, a bed distinctly on the same horizon, this shell 

 is rare, and Cyprina Islaiidica is met with in profusion in entire sliells. At 



