SHELLS OF THE TERTIARY STRATA. 



245 



eocene species have been collected from one small area. 

 Many of the species also abound in the London and Hampshire 

 basins, as at Highgate, the Isle of Sheppey, Hordwell, Alum 

 Bay, and WhiteclifFBay ; and atBognor and Bracklesham, 

 on the Sussex coast. 



I have selected a few specimens from my cabinet, to 

 convey an idea of their usual characters and appearance, 

 (Lign. 38). Although, in mentioning the names of these 

 shells, I do not expect that any but the scientific inquirer 



Lign. 39. — Fresh-water shells of the Paris basin. 



Figs. 1, 2. Bulimus conicus. Figs. 3, 4. Cyclostoma mumia. Fig. 5. 

 Limnaea effilea. Figs. 6, 7* Planorbis euomphalus. Fig. 8, Planorbis 

 cylindricus. 



will endeavour to fix them on the memory, yet it may be 

 useful to point out the forms which prevail in these tertiary 

 beds ; for, as particular fossils are confined to certain strata, 

 the experienced observer can often, at a glance, determine 

 the relative antiquity of a deposit by an examination of a 



