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THE AMERICAN NATURALIST [Vol. LIV 



up at low-tide, and sea urchins and certain sea cucumbers 

 may be obtained by dredging, the expenses connected with 

 their utilization as a whole should be comparatively low, 



making it possible to sell the products at a reasonable 

 price. 



In quoting Lebour, I mentioned Purpura lapillus as a 

 destructive enemy of bivalve mollusks. I now wish to 

 point out the possibility of utilizing destructive gastero- 

 pods: 



Polynices leivisii, a very large gasterpod (Fig. 4), is a 

 great destroyer of mollusks of commercial value. Its foot 

 may reach the length of 21 centimeters and a width of 13 

 centimeters, and a depth of the body about 10| centi- 

 meters. It destroys oyster beds by its burrowing in them 

 in search of clams, but it is not known whether it attacks 

 oysters directly. On account of its burrowing habits, the 

 oystermen, at the head waters of Puget Sound, destroy 

 large numbers of them. 



Keep (1888), speaking of Lunatia leivisii Gld., now 

 merged in Polynices, claims that it possesses a flint drill 



