On the Pliocene Deposits of the East of England. 355 



there obtained, from a seam 10 } T ards long and less than 2 feet in 

 average thickness. 



The three divisions of the Red Crag now proposed (the exact 

 position of the Bentley bed not having been ascertained at present), 

 namely, Waltonian, Newbournian, and Butleyan, are distinguished 

 alike by the difference of their faunas, and by the position which 

 they occupy. The first, with its southern shells, is confined to the 

 county of Essex; the second, containing a smaller proportion of 

 southern and extinct, and a larger proportion of northern and 

 recent species, occupies the district between the Orwell and Deben, 

 and a narrow belt of land to the east of the latter river ; the third, 

 in which Arctic forms such as Cardium grcenlandicum are common, 

 is found only farther north and east. All these beds are believed 

 to have originated in shallow and land-locked bays, successively 

 occupied by the Red Crag sea as it retreated northward, which were 

 silted up, one after the other, with shelly sand. 



The Norwich Crag (Icenian) occupies an area entirely distinct 

 from that of the Red Crag, no instance being known where the one 

 overlies the other in vertical section ; the fauna of the former is, 

 moreover, more boreal and comparatively poor in species. The 

 Arctic species, Astarte horealis, is confined to the northern part of 

 the Icenian area ; its introduction seems to mark a stage in the 

 continued northerly retreat of the sea. The Icenian deposits thicken 

 rapidly northward and eastward, and are believed by the author 

 to constitute part of the great delta-formation of the Rhine. 



The mammalian remains found at the base of the different 

 horizons of the Crag in a rem and e bed, containing material derived 

 from various sources, are considered to be also derivative from 

 deposits, older than the Coralline Crag, formerly existing to the 

 south. 



The Chillesfordian (estuarine), and Weybournian (marine) deposits ; 

 the latter characterized by the sudden appearance in the Crag basin, 

 in prodigious abundance, of Tellina balthica, represent separate 

 stages in the continued refrigeration of East Anglia during the 

 Pliocene period ; but the so-called ' Forest-bed ' or Cromerian (fresh- 

 water and estuarine) with its southern mammalia, and its flora, 

 similar to that of Norfolk at the present day, clearly indicates a 

 return to more temperate conditions, and should therefore be sepa- 

 rated alike from the Weybourn Crag on the one hand, and from the 

 Leda-myalis Sands and the Arctic freshwater-bed of Mr. Clement 

 Reid on the other. The two latter seem naturally to group them- 

 selves together, and with the Glacial deposits. 



The conditions under which the Red-Crag beds originated seem 

 to exist at the present day in Holland, where sandy material 

 brought down by rivers, with dead shells in great abundance from 

 the adjacent sea, is being thrown against and upon the coast, prin- 

 cipally by means of the westerly winds now prevalent. From meteo- 

 rological considerations, it seems probable that strong gales from 

 the east may have prevailed over the Crag area during the latter 

 part of the Pliocene epoch. No other explanation of the accumu- 



