NELSON AND TAYLOR : ON YORKSHIRE MOLLUSCA. 5 1 



In Yorkshire it is found most numerously in the southern 

 districts, and hardly occurs in the northern half of the county, 

 the only known localities being the neighbourhood of Scar- 

 borough, and three widely separated places in Wensleydale. 



According to Lehmann there is no difference in the struc- 

 ture of P. carinatus and P. complanatus^ and that author there- 

 fore considers carinatus as only a variety of the more abundant 

 P. complanatus. 



The Rev. E. P. Knubley, in May 1885, found this species 

 in a sub-fossil state associated with P. complanatus, P. 

 corneus, &:c., on the banks of the River Tutt, two miles south of 

 Boroughbridge, in a deposit two feet below the surface, and 

 about the same time, found it also sub-fossil on the site of an 

 old pond at Staveley. P. carinatus is also found with other 

 species thrown up by the moles, or turned up by the plough on 

 the arable land at Askern. 



3. Vale of York — Common and well distributed about York, Askham, 



Hobmoor, the Foss, 6lc., being its localities, R.M.C., 1881 ; one 

 specimen in a ditch by Foss, above Yearsley Bridge, 1858, W. 

 Whitwell ; Strensall Common, local and not common, W. Hewett, 

 1884 ; Askham Bog, May, 1877 ! pond, Dringhouses, July, 1882, 

 G. Webster ! ditch, Tadcaster ! common in ditches NW. of Church 

 Fenton, Aug. 1881, W.D.R. ! Boston Spa district, J. Emmet, 

 1880 ; Malton, May 17th, 1880, J.D.B. ; pond, Riccal, June, 1879! 



4. Number— Goole, R.D.M., 1876; Howden ! Selby Cut, June, 1879! 



canal, Burton Hall ! Brotherton ! Ferrybridge, J. W. Wood ! pond 

 near Fairburn, June 1885, W. Webster ; wide ditch at Fairburn, 

 July, 1885 ; Knottingley, J.W., 1885 ; pond at Castleford, March, 

 1877 ! pond in the pastures near the new iron railway bridge, Castle- 

 ford, June 15, 1885, G. Roberts. 



5. Hatfleld and r/?or/7e— Plentiful in ditch alongside Black Bank Drain, 



April 14th, 1883, W.D.R. ! R. Torne, several. May 14th, 1883, 

 W.D.R. ! common in Gravel Drain, Auckley, May 14th, 1883 ! 



6. Trent — Doncaster, J.W., 1885 ; Conisborough district, June 2nd, 1873, 



J.W. 



7. Went Vale — Ackworth, a few specimens, C.A., 1854; mill pond, Ack- 



worth, not common, C.A., 1874; Ackworth, J. W.. 1SS5 ; canal, 

 Wintersett, W. E. Brown, 1880; Askern Pool, E. Lankester, 1842 ; 

 Askern, July 2ist, 1881, H.Shaw! Nostell Dam, J.W., 1885; 



