Pleistocene Species 135 



Vertigo minttfissima (Hartm.) now ranges from Finland 

 to Corsica and the Vosges Mountains, while it has been found 

 living in scattered localities in Great Britain from Fifeshire to 

 the Isle of Wight, but not in East Anglia. 



Vertigo pusilla, Mull., concerning whose occurrence in the 

 local gravels there is some doubt, owing to the loss of the 

 single specimen recorded, is found from Perth to north Devon 

 and in the north and west of Ireland. It occurs on the 

 borders of Cambridge in Northamptonshire and West Norfolk 

 as well as in East Suffolk, so that further search will very likely 

 prove it to be still a living inhabitant of Cambridgeshire. 



Vertigo angustior, Jeff., is a rare species which is found 

 in Central Europe and Scandinavia, and in England has been 

 reported from Westmoreland, the neighbourhood of Swansea, 

 Tenby, Bristol and near London. It has been found in the 

 Holocene bed at Harlton mentioned above, so it appears to 

 have lived in Cambridgeshire in the Roman period. 



Succinea oblonga, Drap., is not common in the British 

 Isles, but exists near the coast in Ireland, Scotland, Wales 

 and in Devonshire. 



The following species which no longer live in the British 

 Isles are recorded from the Cambridge district gravels. 



Paludestrina marginata, Mich., lives in France at the 

 present day. 



Pyramidula ruder ata, Studer, is now found in western Asia 

 and apparently in Japan, as well as on the continent of Europe. 



Eulota fruticum (Mull.) now ranges from northern Sweden 

 over the greater part of Europe as well as through Siberia. 

 The disappearance of the last two forms from Britain and 

 their present day wide distribution elsewhere show how much 

 we have to learn regarding the factors which determine the 

 continued existence of a species in any region. 



Clausilia pumila (Ziegler MS.), Pfeiffer, occurs not nearer 

 the British Isles than western Germany. 



Corbicula fluminalis, Miill., one of the Cyrenidae, which 

 occurs doubtfully in the March shell-bearing gravels, now lives 



