54 



water formation on the Isle of Wis^ht, by Prof. Sedg- 

 wick ; it is accompanied with Melaneae fasciala and 

 costata t. 241, Lymnea?, and other shells. 



Should the genus Potamides, to which the above 

 species are referred, continue to be received by Concho- 

 logists, it is likely that many, if not the greater part of 

 Lamarck's 60 fossil Cerites will be referred to it ; for as 

 there are very few in the London Clay in England, it 

 is probable that most of the species he has described 

 belong either to the acknowledged fresh water formations, 

 or to the doubtful or mixed strata known by the name of 

 Plastic Clay, or upper marine formations, such as those 

 of Woolwich, Newhaven, the Isle of Wight, the neigh- 

 bourhood of Paris, &c. 



