PLIOCENE PEEIOD IN ENGLAND. 467 



of separation from the sands of the present stage, yet palaeontologi- 

 cally there is a very clear and satisfactory test for their distinction 

 in the fact, to which I first called attention 16 years ago, that 

 wherever the pebbly sands are fossiliferons they yield Tellina 

 balthica, and in abundance, while this shell is absolutely un- 

 known in any bed of Stage I. The researches of collectors during 

 this time have fully confirmed my statement, while the one or two 

 cases where this shell had been given in publications as from localities 

 in which beds of Stage I. only occur, or at least yield fossils, have 

 been investigated, and been proved to have arisen from clerical 

 errors. The introduction of this shell having taken place so 

 abruptly and in such profusion, it seems evidently to have been due 

 to the northerly depression which I have described opening a com- 

 munication with a part of the sea nearer the Baltic, where this 

 moUusk had lived during the Crag, but from which part some geo- 

 graphical cause had hindered its migration into the waters of the 

 Crag of Suffolk or Norfolk, or into those of the Crag of Belgium, in 

 the beds of which it has never been met with. In every marine 

 bed of the J^orth-Norfolk cliff, from the chalk surface upwards, 

 however, this shell occurs, and it characterizes also all the forma- 

 tions posterior to these wherever they are fossiliferons. 



In tracing the beds of the Stage I am describing southwards from 

 Hopton and Corton CliJf, which is the point furthest south at which 

 we find the Contorted Drift exposed in the coast-section with the 

 identical characters presented by it where lost by descent below the 

 beach-line in the south-east of Sheet 68, we come, after passing the 

 freshwater beds posterior to the Crag, overlain, in Kessingland and 

 Pakefield Cliffs, directly by the gravel c and Chalky Clay, to the 

 low cliff of Covehithe and the two low cliffs of Easton Bavent (all 

 in the north of Sheet 49). These are aU formed by the Chillesford 

 Clay in its greatest thickness, overlain by the red and orange- 

 coloured beds belonging to the lower part of the pebbly sand — the 

 uppermost sands of the Crag, which are white and full of shells, 

 coming up under the clay only in the central one of these three 

 cliffs. At the south end of the southernmost cliff of Eastern Bavent 

 the Chillesford Clay has been cut away, and its place taken by the 

 pebbly sands, so that from this point southwards to the point 

 where the north-east extremity of the line of fig. I. begins these 

 rest on the fluvio-marine Crag, and form the whole or, at any 

 rate, the upper part of the sands of Dunwich Cliff*. In the 

 south-west of Sheet 68 the beds of the Cromer Cliff, in the full thick- 

 ness possessed by them in that part of Norfolk, are cut through by 

 the valley of the Wensum, down which during emergence came the 

 Chalky Clay as in fig. VIII. ; and in this part also we meet with 

 sections showing the unconformability between the Till and the 

 Contorted Drift. Fig. XYI. is taken from one of these, near 

 Yarrow House, Guist (1 J mile south of the line of fig. YIII.), and 



* See last note for the correction of the representation of this Cliff (as 

 Sect. E) given in the Introduction to the * Crag-Mollusca ' Supplement. 



