20 THE DISPERSAL OF SHELLS. 



or the Nepean River, in or near both of which the shell 

 is not at all uncommon. At Burnley, it is said, Planor- 

 bis dilatatiis has occurred in thousands, together with 

 nine other molluscs, Sphceriuvi corneiini, SpJicBriitm 

 lacHstre, Valvata piscinalis^ BytJiinia tentacidata, LinincEa 

 peregra^ Planorbis albiis^ Planorbis corneiis^ Planorbis 

 nitidus, and Planorbis giaber^ in a cistern on the top of 

 an engine-house, " about sixty feet above the canal 

 from which the water is pumped." ' Mr. Musson, on 

 the authority of a member of the Nottingham Naturalists' 

 Society, states that a water-butt on Blue Bell Hill, 

 Nottingham, fed, until about 1882, from the corporation 

 reservoir at the top of Elm Avenue, contained no shells, 

 but when the source of supply was changed from 

 Nottingham to Papplewick, Limncea truncatula soon 

 made its appearance in tolerable abundance, and 

 Ltnincea peregra, also, was discovered. 



Shells are quite commonly found in horse and cattle- 

 troughs, and their occurrence in such places has been 

 noted by many writers. Mr. Roebuck, for instance, 

 mentions having found Limncea pcregra in a new water- 

 trough on the summit of the Great Orme's Head." 

 Mr. W. A. Marsh has referred to the presence of 

 Limncea parva in a horse-trough at his barn-well (in 

 Mercer County, Illinois), nowhere near any pond or 

 slough ; how they happened to be found there, he 

 adds, " remains a mystery." •' Mr. Reid remarks upon 



' F. C. Long, " Science Gossip," xxiv. (1888), 281. 



"- W. D. Roebuck, " Journ. of Conch.," iv. (1884), 209. 



3 \V. A. Marsh, " Conchologists Exchange," ii. (1888), no. 



