of Tertiary Deposits. 539 



which have completely removed this generally superficial fos- 

 siliferous stratum, the bed of the estuary being formed in an 

 older formation. Along the banks of the Deben, which 

 flows through a part of the coralline crag, in some spots 

 the fossil shells line the shore in greater numbers than the 

 recent Testacea; and, during the period in which this estuary 

 has been formed, prodigious numbers of these fossils must 

 have been swept down into the German Ocean, and there in- 

 discriminately mingled with the reliquice of existing species 

 of Mollusca. It is not merely the extent of surface at pre- 

 sent occupied by these estuaries which has thus been denuded 

 of the crag ; considerable tracts of marsh land formerly 

 connected with them, but from which the water has since 

 been shut out, have also lost this original covering. Within 

 a very short distance of the Deben, another estuary, the 

 Stour, flows through a lacustrine deposit belonging to the 

 newer pliocene period ; and here, in addition to the shells, is a 

 considerable stratum of mammalian remains, which at one 

 period evidently extended as far as the opposite bank of the 

 river, a distance of about a mile and a half or two miles. 



"I must now look forward some few thousand years, and an- 

 ticipate the time when, by the recession of the sea, or the eleva- 

 tion of the land, the deposit forming at the mouths of these 

 estuaries has become accessible, and is made the subject of 

 geological investigation. I must also assume that the geolo- 

 gists of that remote period have followed the same course of 

 induction that has recently been pursued, and have arrived 

 at similar conclusions respecting the course to be adopted in 

 ascertaining the relative antiquity of tertiary deposits. The 

 age of the formation in question is about to be tested by 

 comparing its organic remains with the then existing species. 

 Of what will these fossils consist, and whence will they ori- 

 ginally have been derived ? The bones of such animals as are 

 now drifted down the rivers Deben and Stour will be mingled 

 with those of the extinct Mammalia of the newer pliocene 

 period. The living species of Mollusca now inhabiting the 

 German Ocean will be found associated with the extinct Tes- 

 tacea of the newer pliocene, older pliocene, and perhaps even 

 miocene, epoch. Yet this deposit, in which the organised 

 beings of different geological periods shall be found thus in- 

 discriminately mingled, will be one exhibiting every appear- 

 ance of regular stratification ; a deposit in which a large 

 proportion of Testacea will be found naturally grouped, and 

 in which there will be the clearest evidence of their having 

 become entombed on the spot which they had long previously 

 inhabited. That the influence of causes now in operation is 



RR 2 



