APPARENT TRANSMUTATIONS. 203 



tean variations. By reference to the figures, 

 it will be seen that the Paludince and Neritince, 



1, Paludina of lowest horizon ; 2, of the second, and 3 of the uppermost 

 zone. 4, 5, and 6, successive forms of Neritina. 



of the first or lowest zone, have smooth and 

 unwrinkled shells ; that those of the second have 

 their shells belted by a strong fold or corruga- 

 tion, whilst those of the uppermost zone are 

 deeply sutcated, and surrounded by strong spiral 

 ridges. 



Such changes of form take place among Litto- 

 rince and Neritince, even now, in places where 

 alternations of fresh and salt-water affect the 

 mollusca, and in brackish- water localities. There 

 are phenomena in the Cos beds, which warrant 



