212 CHILLESFOED ARCTIC SHELLS. CH.4P. xn. 



obtained in that locality from argillaceous strata twenty feet 

 thick, two only, namely, Nucula Cobboldice and Tellina 

 obliqua, are extinct, and not a few of the other species, such 

 as Leda arctica, Cardium groenlandicum, Lucina borealis, 

 Cyprina islandica, Panopcea norvegica, and Mya truncata, 

 betray a northern, and some of them an arctic character. 



These Chillesford beds are supposed to be somewhat more 

 modern than any of the purely marine strata of the Norwich 

 Crag exhibited by the sections of the Norfolk cliffs NW. of 

 Cromer, which I am about to describe. Yet they probably 

 preceded in date the ' Forest Bed ' and fluvio-marine deposits 

 of those same cliffs. They are, therefore, of no small im 

 portance in reference to the chronology of the glacial period, 

 since they afford evidence of an assemblage of fossil shells 

 with a proportion of between eight and nine in a hundred of 

 extinct species occurring so far south as lat. 53 N., and indi 

 cating so cold a climate as to imply that the glacial period 

 commenced before the close of the newer pliocene era. 



The annexed section will give a general idea of the ordinary 

 succession of the newer pliocene and post-pliocene strata which 

 rest upon the chalk in the Norfolk and Suffolk cliffs. These 

 cliffs vary in height from fifty to above three hundred feet. 

 At the north-western extremity of the section at Weybourne 

 (beyond the limits of the annexed diagram), and from thence 

 to Cromer, a distance of seven miles, the Norwich crag, a marine 

 deposit, reposes immediately upon the chalk. A vast majority 

 of its shells are of living species now inhabiting the British 

 seas, such as Cardium edule, Cyprina islandica, and Scalaria 

 groenlandica, and some few extinct, as Fusus striatus, Tellina 

 obliqua^ and Nucula Cobboldice. At Cromer jetty this for 

 mation thins out, as expressed in the diagram at A ; and to the 

 south we find No. 3, or what is commonly called the ' Forest 

 Bed,' reposing immediately upon the chalk, and occupying as 

 it were the place previously held by the marine crag No. 2. 



