NELSON AND TAYLOR : ON YORKSHIRE MOLLUSCA. 1 5 



Var. radiata, Jeffreys. 



12. Lower Calder—New Miller Dam, J.W., Canal, Agbrigg! River Went, 

 not uncommon, C.A. 



Unio pictorum, (L.) 

 Five varieties of this species are enumerated by Moquin 

 Tandon, in addition to which Dr. Jeffreys and others describe 

 four more, none of which have as yet been recorded as found in 

 Yorkshire. In addition to these, nine varieties are described of 

 U^n'o Reqiiienii, Michaud, a species regarded by Reeve as synony- 

 mous with U. pictorum, L. 



4. Humber—Goole, R.W.M. 



7. Went Vale— River Went. 



8. Dearne — Canal, Barnsley ! Boat pond by Canal, Doncaster, H.F.P. 

 22. Derivent — Scarbro', W.B. 



Unio margaritifer, (L.) 



Margaritana arcuata, Barnes I 



The M. arcuata of Barnes, a native of North America, is 

 synonymous with this species, and frequents rocky streams by 

 preference near the sea coast as in our own country. 



This species belongs to Schumacher's genus Margaritana. 



21. Esbda/e—liiver Esk, plentiful, D. & W. 



22. Denuent—ScsLi-hro', W.B. 



Var. Roissyi, Michaud. 

 Yorkshire, Sowerby (Jeff. Brit. Con., i., 38). 



Var, sinuata, Lamarck. 

 21. Eskdale—Rh-ev Esk, H.C. 



Some authors regard this variety as distinct and place it in 

 another genus — Lyvinuim, Oken — associated with U. pictorum, U, 

 tianidus, Szc, on account of the development of the posterior 

 lateral tooth, and a variety of it — compressa — is described. 



