Page:Natural History, Mollusca.djvu/194

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of the shell, after placing the orifice of its own body-case against that of its victim."

From Mr. Stevenson's interesting account of the erection of the Bell-Rock Lighthouse, we learn that the valves of the Mussel are no defence against the Dog-Winkle.

"When the workmen," says this gentleman, "first landed upon the Bell-Rock, limpets of a very large size were common, but were soon picked up for bait. As the limpets disappeared, we endeavoured to plant a colony of mussels from beds at the mouth of the river Eden, of a larger size than those which seem to be natural to the rock. These larger mussels were likely to have been useful to the workmen, and might have been especially so to the light-keepers, the future inhabitants of the rock, to whom that delicate fish would have afforded a fresh meal, as well as a better bait than the limpet; but the mussels were soon observed to open and die in great numbers. For some time this was ascribed to the effects of the violent surge of the sea, but the Buccinum lapillus [Purpura] having greatly increased, it was ascertained that it had proved a successful enemy to the mussel. The Buccinum being furnished with a proboscis capable of boring, was observed to perforate a small hole in the shell, and thus to suck out the finer parts of the body of the mussel; the valves of course opened, and the remainder of the fish was washed away by the sea. The perforated hole is generally upon the thinnest part of the shell, and is perfectly circular, of a champhered form, being wider towards the outward side, and so perfectly smooth and regular as to have all the appearance of the most beautiful work of an expert