DISPERSAL BY MAN. 223 



of the list published in 1892.^ Mr. Collier stated that 

 he had not tried for some years to get the creature at 

 Pendleton, for when last there the towing-path side of 

 the canal had been undergoing repair, a large quantity of 

 new stones having been put down at the place where 

 the shells used to occur, and the water " had become 

 much worse " ; at Gorton, however, he had found it 

 repeatedly — some in 1883 — but not in great quantity, 

 and not in the original habitat near the cotton- mill, 

 but about a quarter of a mile away where the water 

 was quite cold. In 1886, seventeen years after its 

 discovery at Manchester, the creature was found at 

 Burnley, in the same county^ in the "paper-works 

 lodge" which has no connection whatever with any 

 cotton-blowing machinery, the nearest cotton-mill being 

 half a mile distant. In the following year, it was taken, 

 also, in another Burnley locality, this time under condi- 

 tions similar to those at Manchester, Mr. F. C. Long 

 being reported to have found it, in thousands, in the 

 canal opposite Templets factory, where cotton refuse is 

 blown into the water. It occurred along the canal for 

 over a mile' in the direction of Hapton, but was most 

 plentiful opposite the mill. Mr. Rogers thinks it im- 

 probable that this colony was derived from Manchester, 

 and inclines to the belief that it was founded by 

 shells or ova imported from America,, in the same 

 manner, and at about the same time, as those introduced 

 into the Manchester canals, and he thinks it probable, 



' " Journ. of Conch.," vii. (1892), p. 55. 



