l8 THE DISPERSAL OF SHELLS. 



Co., N. Y., formed by peat-digging some thirty or more 

 years previously, was noted in 1889, by Mr. W. S. 

 Teator.^ 



The presence of shells in reservoirs on high ground 

 has been referred to as indicating dispersal by animal 

 agencies,- but in such cases, I suppose, there is often a 

 possibility that the animals may arrive, perhaps as fry 

 or ova, in the water with which the reservoirs are 

 supplied, and, doubtless, a similar explanation very 

 often applies in the case of shells found in artificial 

 lakes, tanks, cattle-troughs, &c. As illustrating the 

 liability of shells to be carried with water, we have a 

 statement by Mr. Jeffreys that the zebra mussel 

 (Dreissena polymorpha) has been found in the most 

 frequented streets of London after they have been 

 flushed with water from the New River ; and Canon 

 Norman, quoted by the same author, saw immense 

 numbers, in a living state, lining some iron water-pipes 

 which had been taken up in Oxford Street ;^ Mr. Dyson, 

 in 1850, mentioned its occurrence also in most of the 

 large water-pipes supplying Manchester from the water- 

 works at Besvvick, in the reservoir at which place it 



^ See "Nautilus," iii. (1889), 67-9; for a mention of the occur- 

 rence, in 1 88 1, of Margaritana margaritifera (believed to have 

 been absent in 1861), at the island of Anticosti — presenting "a 

 problem in the distribution of fresh-water shells which only the 

 methods of Darwin can surmount" — see A. F. Gray, "American 

 Naturalist," xvii. (1883), 325-6. 



2 See Tate, " Land and Fresh- water Mollusks," 1866, p. 188. 



' "British Conchology," i. (1862), 48; and see also Wood- 

 ward's " Manual," ed. 4, rep. 1890, p. 424. 



