NELSON AND TAYLOR: ON YORKSHIRE MOLLUSCA. 21 



not on her own ; sometimes, but rarely, to stones, or to the 

 shells of other mollusks. Each capsule contains from forty to 

 sixty eggs, but only one embryo is developed, for the other 

 eggs constitute the food of the young Neritina till it quits the 

 capsule." 



3. ^'a/e 0/ Ko/-/f— Common in the Foss, R.M.C. ; Tadcaster, H.C. ! in 



the Wharfe at Boston Spa, W. C. Hey; in the Derwent near 

 Kirkham Abbey, W. C. Hey. 



4. Number — Goole, R.D.M. 



12. Lower Calder — Abundant in the Wakefield and Barnsley Canal at 



Heath I 



13. Airedale — Leeds and Liverpool Canal at Saltaire ! and Bingley ! 

 15, Wharfedale— River Wharfe at Burley, U.S. ! and Otley, H.S. ! 



17. Wensleydale — Abundant under stones, frequently in the most rapid 



part of the River Ure at Hackfall, J. D. ! 



18. Swaledale — Leeming Lane near Bedale, H.C. ! In slovi^ streams at 



Newsham Carr near Thirsk, adhering to Utricularia vulgaris, W. 

 Foggitt, 1855. 



20. Lower Tees — Ballast hills near Middlesbrough (alien), J. W. Watson. 



22. Upper Derwent — Mr. W- Bean, in his List of Scarborough Shells, 

 enumerates this species, but judging from other species named in 

 his list, the area of his investigations must have been very exten- 

 sive. It does not appear in a list for the same place kindly fur- 

 nished by Mr. J. H. Ashford, late of Scarborough. 



24. Holderness — Abundant in the River Hull at Grovehill, where the 

 specimens are thickly encrusted with a calcareous deposit, J.D.B. 

 Barmston Drain, J.D.B. 



Var. nigrescens Colbeau. 



Shell black or blackish. 



3. Vale of York — River Ouse near Bishopthorpe, W. C. Hey ; very com- 

 mon in the River Ouse at York, especially amongst the stones just 

 above the railway bridge, R.M.C. 



Var. trifasciata Colbeau. 



Shell ornamented with three spiral dark bands. 

 17. Wensleydale — One specimen in the River Ure at Hackfall ! 



