NELSON AND TAYLOR : ON YORKSHIRE MOLLUSCA. 39 



Mr. Borrer has remarked that this species has a preference 

 for Callitriche verna in clear water ; other observers give as 

 its favourite habitat the decaying leaves in stagnant pools. 



Rev. W. C. Hey has collected this species in company with 

 P. lineatiis at Dringhouses, and Mr. Roebuck has also found 

 them associated at Hornsea Mere. The fact of their occasionally 

 living in company was not known to Dr. Jeffreys. 



3. Vale of York — Rare in the York district; R.M.C. has found it, but 



not common, in the Foss, and in one pond at Hobmoor, and Mr. 

 C. Wakefield has some he says he obtained from Askham, R.M.C. ; 

 Askham Bog, one specimen, July 1875, W. E. Brown ; Dring- 

 houses Bog, in company with P. lineatus, W. C. Hey ; ponds 

 near Healaugh and Bilbrough, F. G. Binnie; pond, Aketon near 

 Spofforth ! Asp ponds, Knaresborough ! Boroughbridge, J. 

 Wilcock ; Sherburn, 1870, G. Roberts. 



4. Number — Fryston Hall Fish-pond, July ist, 1871, Geo. Roberts and 



J. W. ; pond, Camblesforth ! canal near Burton Hall ! 



7. Went Vale — At Ackworth this species was common in an old roadside 



fish-pond among duckweed a year or two ago, then nearly dis- 

 appeared, but has again increased, C.A. (1854) ; Hessle ! Hems- 

 worth, J.H. ; one specimen in the Went, W. E. Brown ; pond by 

 Hessle Farm near Ackworth, in June 1883, H. Richardson ; a few, 

 associated with P. naiitileus, in a small pond on the right of the 

 road from Ackworth to Bracken Common, G. F. Linney ; associ- 

 ated with P. albiis in Colonel Vincent's pond, Ackworth, G. F. 

 Linney ; South Elmsall, 1875, J-W. ; the pool at Askern, 1879, 

 J.W. ; river Went, between Campsall and Askern, J.W. 



8. Dearne — Bretton Park, common, W.D.R. ! 



10. Colne — Canal near Huddersfield, J.Wh. ; Deighton, common, J.Wh. 



11. Upper Colder — Luddenden Valley, J. C, 1875, 



12. Lower Calder — Kirkthorpe, J.H. ! pond between Crofton and Nostel, 



1869, J.W. ; Barnsley canal, several, J.W. 



13. Airedale — Canal at New Wortley, H.S. ! goit at Meanwood, one speci- 



men, H.S. ! stream in Goodman-street, Hunslet, 1861, now built 

 over ! 

 20, Lower Tees — Occurs plentifully in a small pond at Acklam, near 

 Middlesbrough, B. Hudson. 



22. Upper Derwent — Pond in ' Plantation,' Scarborough, C.A. 



23. Chalk Wolds — Bridlington, W. C. Hey ; Bridlington, common attached 



to caddis cases in a pond near railway, west side of line to Scar- 

 borough, April I2th, 1884, G. Wingate ! sparingly in Leckonfield 

 Moat, J.D.B. ! 



24. Holderness — Hornsea Mere, J.D.B. ! 



