CHAP, iv.] BRITISH PLEIOCENE STRATA. 71 



British Pleiocene Strata. 



The Pleiocene strata of Britain, known as the 

 Crags of Norfolk and Suffolk, extend over the eastern 

 parts of those counties and over north-eastern Essex, and 

 consist of sands and gravels more or less impregnated 

 with iron, containing numerous shells, most of which 

 are still living in our seas. They contain also singular 

 accumulations of fossil bones, derived from the break-up 

 of several different formations. In the phosphatic or 

 coprolitic deposit, for example, of the Red Crag, there 

 are fossil sharks, rays, and crabs from the London Clay, 

 and fragments of land mammalia, such as the Hycenarc- 

 tos, which have been derived from the destruction of 

 Meiocene strata, in the area now occupied by the North 

 Sea. There are also water-worn fragments of teeth, and 

 bones of the Pleiocene mammalia, derived from the de- 

 struction of old land surfaces, in the Coralline and Red 

 Crags, as well as in that of Norwich. These strata, 

 therefore, are the marine equivalents of the accumu- 

 lations on the borders of ancient lakes, and in the 

 ancient river valleys, which have afforded so rich and 

 varied a Pleiocene fauna and flora in France and Italy, 

 although in point of time they may be referred to the 

 later, rather than the earlier, stage of the Pleiocene, 

 because the mammalia which they contain have been 

 washed out of the strata in which they were originally 

 buried. The mammalia, however, of the Norwich Crag 

 are considered by Professor Prestwich to be 1 in part 

 undisturbed. The lower portion of the mammaliferous 

 deposit at Thorpe, near Norwich, seems to me to be 

 an isolated fragment, which happens to have been spared 



1 Quart. Jour. Geol. Soc. Lond. xxvii. p. 479. 



