26 NELSON AND TAYLOR: ON YORKSHIRE MOLLUSCA. 



Mr. R. M. Christy, writing of it in the River Ouse at York, 

 says "when the river is at its full height they are difficult to get, 

 but when lowered they can be procured in any quantity. Above 

 York it is not uncommon, but below it is clustered round the 

 mouths of some small ditches on the Bishopthorpe side. No 

 doubt they preferred the sewage and filth that was in the water. 

 One specimen was obtained 40 mill. long. 



Dr. Jeffreys says that the Rev. Dr. Gordon has found 

 this species at Findhorn, in the Moray Firth district, but Dr. 

 Gordon expressly states it to have been a dead ballast shell, 

 and not indigenous to the locality. 



P. vivipara seems from our experience to ascend after 

 midday from the depths of the canal or river and approach 

 more closely to the surface. We have observed this peculiarity 

 at different times. In the early morning all were deep in the 

 water or resting on the bed of the canal, but as the day 

 advanced they crawled into the shallows or ascended the canal 

 sides to the surface. 



Heaps of broken shells are sometimes found by the canal 

 sides, evidently destroyed by rats. 



3. Vale of York — Profusely abundant in a stony part of the River Ouse 



below York, very fine in the Foss, Rev. W. C. Hey. 



4. Number — Very abundant in the canal at Selby, in the places bare of 



vegetation, amongst the mud and stones ! Goole, R.D. M. ; in 

 disused lime pits formerly connected with the river at Brotherton, 

 not very common ! 



7. Went Vale — Madder Close, Askern, E. Lankester, 1842. 



8. Dearne — Wombwell, near Barnsley, H.C. ! Wakefield and Barnsley 



Canal at Barnsley, A.P.T. ! near Doncaster, Rev. W. Hincks, 

 1840. 



12. Lower Oalder — Pretty common in the Wintersett Canal, W. E. Brown ; 



New Miller Dam, J.W. ; Wakefield and Barnsley Canal at Wake- 

 field I at Agbrigg ! near Heath Common ! Royston ! and between 

 Walton and Cold Hiendley, A.P.T. ! rarely in a stream near 

 Sandal Castle, J.H. 



13. Airedale — Aire and Calder Canal at Swillington, H.S. ! 



Trans.Y.N.U., 18S0 (pub. 1883). Series C 



