263 NEOZOIC TIME. [CHAP. XIII. 



places marine shells of species which now live on neigh- 

 bouring shores. These deposits occupy areas from which 

 the older clay appears to have been removed, and no clear 

 section has yet been found where the one clay overlies the 

 other, but there are several localities where the relative 

 ages of the two clays can be inferred from their relative 

 positions, and in every case the evidence points to the con- 

 . elusion that the chalky clay is older than the red and 

 brown clays. 1 



The most recent and most detailed observations on the 

 later Glacial series of Yorkshire, 2 Lincolnshire, 3 Cheshire, 4 

 and Lancashire, 5 have shown that the supposed division of 

 these beds into an upper and lower Boulder-clay, separated 

 by a set of marine sands and gravels, is incorrect, the sands 

 and gravels being only lenticular beds and occurring at 

 various horizons in the series. 



The southern limit of these newer clays in the Midland 

 counties has not yet been definitely ascertained, but pro- 

 bably they do not extend far to the south of the valley of 

 the Trent and its tributaries. It is worthy of mention also 

 that clay which closely resembles the red (Hessle) clay of 

 Lincolnshire occurs in the north of Norfolk, and occupies 

 a narrow strip of low ground between Hunstanton and 

 Wells. 



Plateaux Gravels and Raised Beaches. South of the area 

 covered by the later Boulder-clays the latest G-lacial deposit 

 is a coarse gravel, consisting chiefly of quartzite pebbles 

 from the Trias and of flints from the Chalk, a deposit which 

 has the appearance of having been formed, partly from the 



1 See " Quart. Journ. Geol. Soc.," vol. xli. p. 114 et seq. 



2 " Geology of Holderness," C. Reid, " Mem. Geol. Surv.," 1886. 



3 " Geology of East Lincolnshire," 1887, p. 76, and " Quart. Journ. 

 Geol. Soc.," vol. xli. p. 114. 



4 A. Straban, " Quart. Journ. Geol. Soc.," vol. xlii. p. 369. 



5 Mellard Keade, " Quart. Journ. Geol. Soc.," vol. xxxix. p. 83. 



