Ch. XL] 



ASSOCIATED FRESHWATER STRATA. 



133 



table matter, and are divided into thin layers. The imbedded shells be- 

 long to the genera Planorbis, Lymnea, Paludina, Unio, Cyclas, and 

 others, all of British species, except a minute Paludina, now inhabiting 

 France. (See fig.. 117.) 



The Cyclas (fig. 118) is merely a remarkable variety of the common 

 English species. The scales and teeth of fish of the genera Pike, Perch, 



Fig. 118. 



Cyclas (Pisidium) amnica, var. ? 

 The two middle figures are of the natural size. 



Roach, and others, accompany these shells ; but the species are not con- 

 sidered by M. Agassiz to be identical with known British or European 

 kinds. 



The series of formations in the cliffs of eastern Norfolk, now under 

 consideration, beginning with the lowest, is as follows : — First, chalk ; 

 secondly, patches of a marine tertiary formation, called the Norwich 

 Crag, hereafter to be described ; thirdly, the freshwater beds already 

 mentioned ; and lastly, the drift. Immediately above the chalk, or crag, 

 when that is present, is found here and there a buried forest, or a stra- 

 tum in which the stools and roots of trees stand in their natural position, 

 the trunks having been broken short off and imbedded with their 

 branches and leaves. It is very remarkable that the strata of the over- 

 lying boulder formation have often undergone great derangement at 

 points where the subjacent forest-bed and chalk remain undisturbed. 

 There are also cases where the upper portion of the boulder deposit has 

 been greatly deranged, while the lower beds of the same have continued 

 horizontal. Thus the annexed section (fig. 119) represents a cliff about 



Fig. 119. 



Gravel 



.*.-,•■*•- ;..*«'•-•_ r^TT-rrr: — r~Z? - 



m 



Sand 



C3l5€f/iSS 



Loam 



r~ jS s ss J '' yy 



Till 



^ -±%%* * -o «;o 



<3 



Cliff 50 feet high between Bacton Gap and Mundesley. 



50 feet high, at the bottom of which is till, or unstratified clay, contain- 

 ing boulders having an even horizontal surface, on which repose con- 

 formably beds of laminated clay and sand about 5 feet thick, which, in 

 their turn, are succeeded by vertical, bent, and contorted layers of sand 

 and loam 20 feet thick, the whole being covered by flint gravel. Now 

 the curves of the variously colored beds of loose sand, loam, and pebbles 



