NOTTINGHAMSHIRE SUBFOSSIL MOLLUSCA. 1 63 



* P. spirorbis Pupa umbilicata 



* Limnaea peregra v. ovata * P. marginata 



* L. palustris * Vertigo pygmaea, &c. 



* L. truncatula * Cochlicopa lubrica 



* Succinea elegans * Achatina acicula 



Mr. Gain also found on a previous visit a single specimen 

 of Cyclostoma ele:^ans. This layer is succeeded by three or 

 four feet of a Tufa exactly similar to the ' petrified moss ' on 

 sides of rocks at Larnbley Dumble, &c. , covering the sides of 

 the dumble close to the water. This deposit is tolerably hard 

 and compact and in it the stems of reeds and grass are most 

 distinctly seen. 



This succession Mr. Gain has also seen at Cirassthorpe and 

 near Egmanton. It appears to be the remains of what was 

 once a long narrow strip of boggy land followmg the course of 

 the stream from Egmanton down to nearly as far as the alluvial 

 deposits in the Trent valley, but is above the level of the latter, 

 and about three miles in length. At Grassthorpe Mr. Gain has 

 found the following species : — 



Sphserium corneum Succinea elegans 



Anodonta anatina Zonites cellarius 



(one valvej Z. nitidus 



Bythinia tentaculata Z. fulvus 



Planorbis spirorbis Helix nemoraiis 



P. complanatus H. concinna 



Limnaea peregra H. hispida 



L. palustris H. pulchella 



L. truncatula Cochlicopa lubrica 



In each case given, the streams which have brought and 

 deposited these alluvial tracts rise on Keuper clay ground. 



