182 OLDKR PLIOCRNK PERIOD. [Ch. XIII. 



of England, which may, therefore, have been formed when 

 the testacea of the older Pliocene period were in existence. 



Upon the whole, we may imagine the crag strata to bear a 

 great resemblance to the formations which may now be in pro- 

 gress in the sea between the British and Dutch coasts, a sea 

 for the most part shallow, yet having here and there a depth of 

 50 or 60 fathoms, and where strong tides and currents prevail ; 

 where shells, also, and zoophytes abound, and where matter 

 drifted from wasting cliffs must be thrown down in certain 

 receptacles in the form of sand, shingle, and mud. 



In conclusion we may observe that the history of the crag 

 requires further elucidation, and the author is by no means 

 satisfied with the sketch above given ; but as the country is so 

 accessible and the formation so interesting both in its structure 

 and zoological characters, it is hoped that these remarks may 

 excite curiosity and lead to fuller investigation. 



Sheppey. Ramsyate. Brighton. Deposits have lately 

 been observed by Mr. Crow * resting on the London clay, 

 in the Isle of Sheppey, at the height of 140 feet above the sea, 

 and by Captain Kater at Pegwell Bay, near Ramsgate, at the 

 height of a few yards, and by Mr. Mantell, in the cliffs near 

 Brighton, all containing recent marine shells. But as there are 

 only five or six species yet discovered in these localities, we 

 cannot decide, till we obtain further information, whether these 

 strata belong to the crag or to a more recent formation. 



* Of Christ Church College, Cambridge. 



