DISPERSAL BY MAN. 197 



the occurrence of " a well conserved shell of Helix 

 aspersa in some imported sand near Langesund." A 

 shell of Helix ericetomm once found near Christiania, 

 this author suggests, may have been imported " among 

 sand brought with vessels from England or France." ^ 

 It seems almost certain that the creatures are occa- 

 sionally carried many miles with railway ballast, with 

 chalk, etc., used in making sea defences and other 

 embankments, with earth and other substances trans- 

 ported for horticultural purposes, etc. Thus the Kentish 

 snail {Helix cantiana), abundant on railway-banks near 

 Hartlepool, " may have been introduced in ballast ;" ^ 

 Helix virgata, found plentifully on embankments 

 between Pevensey and Bexhill, where the London, 

 Brighton and South-coast Railway runs close to the sea, 

 was probably brought, as the Rev. S. Spencer Pearce 

 states, with the chalk forming the embankments, which 

 is believed to have come from the Eastbourne cutting, 

 some eight or nine miles away ; the same snail, accord- 

 ing to another observer, noticed in several places on 

 railway-banks also in Sussex "was probably brought 

 with chalk ;" a colony of Helix cartusiana, also, known 

 to have existed for some years at Cowfold, in the 

 same county, and now extinct, is believed to have 

 been originally introduced with chalk.^ Helix virgata, 



» B. Esmark, " Journ. of Conch.," v. (1886), p. 106. 



"" "Naturalist," 1886, p. 148, quoting J. E. Robson, "Young 

 Nat.," V. (1884), p. 192. 



2 W. Borrer, cited by J. E. Harting, '' Zoologist," (3), ii. (1878), 

 p. 92. 



