28 NELSON AND TAYLOR : ON YORKSHIRE MOLLUSCA. 



which may possibly be the vdiUeiy producta of Menke, but we 

 have not seen specimens of either. 



The ova of this species have been described as being placed 

 in three long rows. According to our observations this is not 

 always the case. Some specimens collected in July deposited 

 ova a few days afterwards, in two rows of about eleven eggs 

 each, terminating in single ones. The gelatinous envelope of 

 each egg was pentagonal in shape, the acute angles always 

 directed inwards and alternating with each other, the nucleus 

 small and of a yellowish colour, and placed near one side, the 

 terminal ones round, except where joined to those contiguous. 

 The capsules were transparent, and the total length was about 

 iSmill., the breadth 3mill. 



B. tentaciilata appears to have in some degree the peculi- 

 arity of P. vivipara of ascending to shallower water after mid- 

 day. 



According to Mr. G. S. Tye, who has given some attention 

 to the subject, this snail suspends itself after floating by a 

 mucous thread, which is usually attached to the surface of the 

 water. 



Subfossil specimens are thrown up by the moles about 

 Askern, where it is in immense quantities beneath a thin 

 stratum of peat and underlaid by calcareous tufa. 



1. Mersey — Greenfield Canal, J.Wh. 



2. Lune and Ribble — Common in a pond close to the River Ribble at 



Gisburn, W.D.R. ! 



3. Vale of York — Common and fine in a dyke near Church Fenton, H.P. ; 



common in Bishop Dyke and various ditches near Hambleton ! and 

 Milford 1 common in a dyke at Ryther, H.P. ; Tadcaster, H.C. ! 

 unusually fine in Askham Bog, near York, W. C. Hey ; River 

 Foss, W. C. Hey ; dead shells among mud &c. thrown out of the 

 Foss Beck near Catterton, F. G. Binnie ; Hobmoor, near York, 

 R.M.C. 



4. Number — In a ditch near the canal and in the canal at Selby ! Milford, 



in ditches! Goole, R.D.M. ; Drax, R.D.M. ; Camblesforth, 

 R.D.M. ; Howden ! F. Emsley, of Leeds ! stream at Castleford ! 



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



