101 



moisture necessary for its existence, by change of position. Succinea, 

 of wliich we find no adult specimens, unless they are of stunted 

 growth, or that the outer portion of the shell from its extreme 

 tenuity and fragility has not been preserved, is a truly amphibious shell, 

 frequenting rank herbage, in the most humid situatioDS, and occasionally 

 without any apparent necessity, immersing itself in the rUl or pond m 

 whose vicinity it exists. 



A Pisidium, which from its want of concavity appears to coincide 

 more nearly with the descriptions of P. cinereum than that of obtusale, 

 and P. pusillum, are the only other water shells found here— both being 

 foimd in small ponds in many situations. 



From the consideration of the preceding Hst of MoUusca, the conditions 

 under which the deposit was made suggest themselves with a certain 

 degree of clearness. There were probably thickets near, and moss-clad 

 soil, from which, as they dropped and died, the Helix nemoralis and 

 Cyclostoma were washed by storm torrents to a lower level. A toiTent 

 of sufficient force to disturb and finally entomb these, would more easily 

 scour the mosses of the damp uncultivated district over which it com-sed, 

 bearing from their habitats in numbers proportioned to their smallness, 

 the others named in the list, as CarycUum, Pupa, Zonites, and Zua. 



The Pisidium and Linmoeus, from their active and hardy habits, are 

 precisely the shells which we might expect to find in such a locality. 



A somewhat similar assemblage of shells may be found in the small 

 boggy patches, which are still in the course of formation upon the sides of 

 May Hill, under circumstances closely analogous to those suggested in 

 the older instance. The space of time during which these operations of 

 nature have continued, can only be duly estimated by those who have 

 carefully inspected the deposit, and examined the material of which it is 

 composed. 



It was om- intention to have examined the finer portion into wldch it 

 resolves itself in water, for Diatomacese, but the short time afibrded by 

 the interval between our visit and tliis meeting has not permitted us to 

 fulfil it. 



The conditions requisite to form such a deposit at this spot have long 

 ceased to exist, but it is not improbable that the elevating or disturbing 

 force, which has given to the Cotteswold range its normal dip of about 

 two degrees to the S.S.E., exerted itself subsequent to the deposition of 

 this sedimentary bed, for which opinion reasons may be assigned ; and 

 this would have sufficed to alter the entire character and direction of 

 its water-collecting system. The application of this remark may not be 

 readily apparent, but, looking across the Severn to the hills of the Forest 



