CHAPTEE XII. 



ICENIAN PERIOD. 



PHE reasons for grouping the Miocene, Pliocene, and 

 * Pleistocene deposits into one system have been given 

 elsewhere. 1 Their geographical extension is entirely diffe- 

 rent from that of the older (Hantonian) Tertiaries ; the 

 later Miocene and the older Pliocene deposits of the conti- 

 nent are so intimately connected that it is often difficult to 

 separate one from the other, while the close relations of the 

 Pliocene and Pleistocene are universally admitted. As, 

 however, the treatment of the Pleistocene epoch involves a 

 consideration of the Ice Age and the many debatable 

 questions connected with the Glacial deposits, it will be 

 more convenient to consider the geographical changes which 

 took place during the Miocene and Pliocene epochs first, 

 and to discuss the complicated phenomena of the Pleistocene 

 in a separate chapter. 



1. Stratigraphical Evidence. 



Miocene Epoch. Throughout both the Oligocene and 

 Miocene epochs the greater part of Britain remained in the 

 condition of dry land, and no actual Miocene deposits have 

 been found either in Britain or in the north-eastern part 

 of France. They occur in southern and western France, 

 and patches of them exist as far north as the Cotentin in 

 Normandy. Lately, also, it has been decided that certain 

 1 " Historical Geology,'' by the author, pp. 36 and 486. 



