DISPERSAL BY MAN. 215 



1838, Mr. Strickland pointed out that it multiplied 

 with astonishing rapidity, and, in a few years, he 

 thought, it would probably become one of our com- 

 monest molluscs. On visiting the Commercial Docks, 

 the original British habitat, in or about that year, he 

 saw a vast number of the shells in the depot for 

 bonded timber ; at least one generation, evidently, had 

 passed away since the introduction, for dead-shells 

 were scattered over the bottom and served as points of 

 attachment for the byssi of the living ; it would be 

 interesting, he remarked, to watch the gradual spread 

 of the species over the kingdom.^ About the years 

 1 83 1 -3, we find, it was discovered in great numbers 

 at Goole, Yorkshire, in docks belonging to the Aire and 

 Calder Company, opened only three or four years pre- 

 viously. On the water being drawn off a few feet 

 lower than usual, the walls were seen to be "completely 

 covered " with shells, pecks of which might have been 

 procured. One of the docks was used entirely for the 

 bonding of foreign timber which frequently remained 

 therefor some months before being re-shipped or floated 

 upon rivers and canals to various inland towns, and 

 during such periods, it is said, those pieces which ad- 

 joined the sides or touched the bottom were sure to 

 become covered with shells, which, thus, might easily be 

 carried to the various districts communicating with the 

 canals of the Aire and Calder Company.- About this 



' H. E. Strickland, Charlesworth's " Mag. Nat. Hist.," (n. s.), ii. 

 (1838), pp, 362-3. 

 * R. J. Bell, " Zoologist," i. (1843), p, 253. 



