3© NELSON AND TAYLOR : ON YORKSHIRE MOLLUSCA. 



Var. albida Rimmer. 



Shell white. 

 4. Number — One spechiien in a sluggish stream at Castleford in li 



Var. ventricosa Menke. 

 7. Went Vale — Askern district, J.W. 



Monst. decol latum Jeffr. 



4. Humber — Stream at Castleford ! 

 7. Went Vale — Askern, J.W. 



10. Co//7e— Plentiful in the Elland Canal, J. Wh. 



11. Upper Calder — Plentiful in the Huddersfield Canal, J. Wh. 



12. Lower CaWer— Plentiful at Kirkthorpe, J.H. ; New Miller Dam, J-W. 



Bythinia Leach ii (Sheppard). 



Local and occasionally abundant. 



Subfossil specimens of this species are thrown up by the 

 moles about Askern. 



3. Vale of York — Common but not fine in the River Foss and the small 



stream running into it at the third lock from its junction with the 

 Ouse, R.M.C. 



4. //M/Mbe/-— Snaith, R.D.M. ; Drax, R.D.M. ; Knottingley, J.W. ; ditch 



near Gateforth ! abundant amongst decaying vegetation in the 

 Selby Canal at Selby and near Burton Hall ! ditch at Bub with, 

 J.G. ! 



5. Hatfield and Thome — Common in a ditch parallel with Black Bank 



Drain, W.D.R. ! 



6. Trent — Conisborough, J.W. 



7. Went Vale — Askern Pool, E. Lankester, 1842 ; plentiful in a ditch at 



Askern ! Nostel Lake ! 

 12. Lower Calder — Found commonly amongst decaying sedges at the sides 

 of the Wakefield and Barnsley Canal, J.H., at Agbrigg, H.P., and 

 at Oakenshaw ! New Miller Dam, J.W. 



Trans. Y.N. U., 1880 (pub. 1883). Series C 



