236 NEOZOIC TIME. [CHAP. XII. 



deposits in Belgium are of Miocene age these are the 

 sands of Antwerp and the Bolderberg, which rest un- 

 conformably upon the Oligocene (Rupelien) clay, and have 

 a pebbly basement bed which contains flints and rolled 

 septaria ; the lower part of these sands is very dark and 

 argillaceous, and contains many shells in the position of 

 life ; the higher sands are less argillaceous, but still dark 

 coloured from the presence of glauconite, and the whole 

 group was formerly termed the " black crag." 



There is some reason for thinking that similar deposits 

 originally extended across the North Sea into the east of 

 England, for the pebble beds at the base of the Suffolk 

 Crags contain nodules of greenish or reddish-brown sand- 

 stone, which enclose casts of some of the " black crag " 

 fossils. 1 Professor Ray Lankester has also recorded teeth 

 of a Mastodon whale and shark (Carcharodon) in the same 

 matrix, and he is of opinion that many of the mammalian 

 bones found in these nodule beds have been derived from 

 strata of Miocene age, of which no other traces now 

 remain. 



Pliocene Epoch. The Pliocene series is divisible into an 

 older and a newer group, and the British beds of this age 

 may be classified as follows : 



Newer. I Forest Bed Grou P- 



' ( Norwich and Red Crags. 



f St. Erth Beds. 

 Older. < Coralline Crag. 

 I Lenham Sands. 



The oldest Pliocene deposits in England are certain fer- 

 ruginous sands which at Lenham and other places on the 

 North Downs in Kent and Surrey are at or above the level of 

 600 feet. They were first described by Professor Prestwich 

 in 185 7, 2 and correctly referred by him to the Pliocene, but 



1 Ray Lankester, " Quart. Journ. Geol. Soc.," vol. xxvi. p. 493. 



2 " Quart. Journ. Geol. Soc.," vol. xiv. p. 322. 



