A HISTORY OF DURHAM 



Planorbis spmrb'u, MUll. 

 — contortm (Linn.) Local : Ryton Haughs ; 

 near Stockton 



— fonlanus (Lightf.). Rather rare : Middleton- 



one-Row ; Stockton 

 Physafont'tnalis (Linn.) 



— hypnorum (Linn.) 



IL PROSOBRANCHIATA 



Paludestrina stagnalh (Bast.). Mouth of the Tees ; 



Seaton Carew 

 Bilhynia tentaculata (Linn.) 

 Valvata piscinalis (Mull.) 

 — cr'utata, MuU. 

 AcUuh lineata (Drap.). Rare : Castle Eden Dean 



B. PELECYPODA 



Unto margantifer (Linn.). In the head waters of 



some streams 

 Anodonta cygnaa (Linn.) 

 Sphcerium corneum (Linn.) 



— lacustre (Mall.) 



Ptstdium amnicum (Mtill.). Rare : near Stockton- 

 on-Tees, Jesmond Dean 



— pusillum (Gmel.). Besides the typical form the 



variety, by some held to be a distinct 



species, P. obtusak, has been taken near 

 Darlington 

 Pisldium tiitidum, Jenyns. Near Darlington 



— fontinak (Drap.). In addition to the typical 



form, the variety P. pukhellum, by some 

 held to be a distinct species, is plentiful 



— milium (Held.). Brastide, near Durham ; 



Ryton Haughs 



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