o06 GEOLOGY OF THE ISLE OF WIGHT. 



mud spread over the bottom of still lakes is covered 

 with their exuviae. The largest living Cypris, 

 does not exceed one-sixth of an inch in length. 

 In a fossil state these cases appear like minute, 

 white, elliptical, or reniform scales, on the surfaces 

 of the recently separated laminae of clay, shale, 

 and limestone. After exposure to the weather the 

 cases decompose, and leave the surface of the stone 

 covered with their casts, which appear as minute 

 polished tubercles ; some layers of the compact 

 ironstone have a granulated appearance from the 

 abundance of these remains. Three species of the 

 Wealden Cyprides are represented in lign. 25. 



The immense accumulation of the remains of 

 these crustaceans in the Sussex marble is quite 

 surprising; some slabs which I have examined 

 under the microscope, have the shells and their 

 interstices literally crammed with whole and broken 

 cases. As the recent species inhabit either still 

 lakes or gently flowing streams, and not the tur- 

 bulent waters of estuaries, it follows that sediments 

 largely charged with the exuviae of cyprides must 

 have been deposited in lakes, or bays, or in tran- 

 quil streams, communicating with the flood of 

 waters which transported to their present situation 

 the bones of terrestrial animals and plants. These 

 beds of fluviatile shells and cyprides, with scarcely 



