Northern Cambridgeshire 123 



woods which border the Roman Road over the Gogmagogs, 

 e.g., Sphy radium edentulum, Jaminia muscorum and Vertigo 

 pygmaea. 



In the above an attempt has been made to indicate the 

 characters of the molluscan fauna of Cambridge itself and of 

 places within easy reach in an afternoon's excursion. Certain 

 cases of isolated occurrence in the neighbourhood will be 

 mentioned later on. 



The molluscan fauna of Ely seems to be much the same as 

 that of the Cambridge district. The less contaminated state 

 of the river at the former place is probably the reason for the 

 greater abundance of the larger bivalves there noticeable. 

 Vivipara contecta and Limnaea stagnalis seem to occur more 

 frequently at Ely than at Cambridge. The trees of the 

 Cathedral Close have been mentioned by Mr L. E. Adams 1 

 as a good locality for the species of Helicella. Littleport on 

 the Ouse five miles north of Ely is recorded as a locality for 

 Planorbis crista, while Dreissensia polymorpha attached to 

 living Anodonta cygnaea has also been obtained there. 



As has already been stated the central and northern 

 portions of Cambridgeshire seem to have been but slightly 

 searched. Of Streptoneurous forms Paludestrina jenkinsi has 

 been found in the Wisbech Canal and in the Nene near Foul 

 Anchor Ferry, and in the last-named locality P. stagnalis also 

 occurs. The Wisbech Museum has a specimen of Vivipara 

 vivipara from the district. Besides most of the species already 

 mentioned as occurring commonly or fairly commonly in the 

 neighbourhood of Cambridge, and in the Cam and Ouse down 

 to Ely, the Samuel Smith and other cabinets in the Museum 

 have local examples of Balea perversa, Clausilia bidentato, 

 Sphaerium lacustre, Pisidium amnicum and P. pusillum. 

 Planorbis crista and P. spiroi~bis also occur in this district, 

 while very fine examples of Aplecta hypnorum have been 

 obtained at Grip, near March. At present, however, our 

 knowledge of the mollusca fauna of the fen district of 

 1 Journ. Conch., vi., 1890, p. 277. 



