PEARCE AND MAYFIELD : MOLLUSCA OF EAST NORFOLK. 403 



Van compressa Jeff. Most abundant at the bends of the 

 River Yare near Surlingham Ferry and Bramerton Woods 

 End. At low tides it is possible to obtain hundreds with the 

 hands, and there is represented in this locality every grada- 

 tion of form between the type and this remarkable variety 

 (S.S.P.). Mr. Bridgman, in 1872, was the first to notice 

 this variety, and in his list thinks that its distinctive form 

 " may be caused by the swiftness of the current carrying 

 " away the loose particles of soil and leaving a very hard 

 " bottom for the shell to live in." 



Anodonta cygnea L. In the River Wensum at Heigham 

 and Hellesdon (A.M.); in the Yare and Bure Rivers — in 

 the former at Postwick and Bramerton, etc., and in the 

 Bure everywhere above Acle (S.S.P.). 



A. anatina L. In the Wensum at Heigham and Hellesdon 

 (A.M.); in the Rivers Yare and Bure (S.S.P.). 



Sphserium corneum (L.). Common in Yare and Bure 

 Valleys ; ditches, Bramerton, Surlingham Ferry, Whitling- 

 ham Marsh, Brundall, Stoke Holy Cross, Acle, Halvergate, 

 Horning Ferry, Thurne Stream, Old Meadow Dyke, 

 Salhouse and Ranworth Broads (S.S.P.) ; ditches at 

 Colney, Haynford, Costessey (A.M.). 

 Var. flavescens (Macgill.). Horning Ferry, Brundall 



(S.S.P.) ; Colney (A.M. 



Var. nucleus (Stud.). Near Bramerton and Whitlingham 



(S.S.P.). 

 Var. pisidioides Gray. Ditches at Brundall (S.S.P.); and 

 Colney (A.M.). 



S. lacustre (Miill.). More local than preceding, but plentiful 

 in both Bure and Yare valleys. Surlingham Ferry, Brun- 

 dall, Horning Ferry (S.S.P.) ; Thorpe, Old Lakenham, and 

 Colney (A.M.). 



Pisidium amnicum (Miill.). In the River Yare at Bramer- 

 ton, Brundall, Coldham Hall, as well as in the tributary 



