410 THE ZGOLOOIST. 



Points," were laid on the beds. From their inception living 

 groups of the so-called " Slipper Limpets " {Ci'epidula fornicata) 

 were seen adhering to the Oysters. At first not much notice 

 was taken of them, though Bridge, thinking they might be 

 saleable, cleaned some and took them «Bo London, but he could 

 find no market, and there the matter dropped. Gradually, 

 however, they increased in numbers on the grounds, and now 

 are scattered broadcast in *' The Bay " (adjoining Canvey Island), 

 and along the shore to right opposite Westcliff. Few compara- 

 tively are found on the sandy flats, but they are innumerable on 

 the sides of the rivulets and near the muddy ground towards 

 low- water mark, where they seem to thrive amazingly. Further 

 down the estuary, namely, at the shore-mouth of the Swale, 

 many years back, American Oysters were there relaid. As time 

 passed the Crepidulcs therefrom flourished and spread about, 

 finally invading the Sea Salter and historic " Boyal Whitstable 

 Natives " beds. This, notwithstanding the great care and labour 

 bestowed on the culture of these beds by constant dredging, 

 weeding, and selection of the " ware," &c. Incidentally, it may 

 be added that A. S. Kennard* has intimated his finding Crepi- 

 dula fornicata near Heme Bay, where also E. F. Wheeler 

 (Fishery Officer) tells us they are to be got. The whitebaiters in 

 Queenborough neighbourhood (mouth of the Medway) also occa- 

 sionally get the shells in their drag-nets. 



To sum up, it goes without saying that the " Slipper Lim- 

 pet" or "Boat Shell" has now established itself firmly, and 

 become naturalized t and acclimatized in nearly all the Oyster- 

 grounds of Essex and Kent. With our present knowledge it 

 would seem as if it were beyond the power of man to root 

 them out. 



It now comes to the essential, practical issue of the facts ; 

 otherwise expressed: Are the " Limpets " to be classed among 

 the vermin of the oystermen, or is their influence to the good, 

 bad, or indifferent ? 



Public attention has been drawn to the topic by the occur- 



* Proc. Malacol. Soc. vol. ii. p. 134 (1896). 



f Alfred Eussel Wallace lays some stress on the distinction between 

 Naturalization and Acclimatization (see his article in ' Encyclopaedia Britan- 

 nica ' (9tli ed.), vol. i. p. 84). 



