Page:Natural History, Mollusca.djvu/204

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the last whorl of the shell, but Mr. Adams from observation on the living animal, informs us that it is entirely enclosed and covered by the thin shell, while the foot is narrow, slender, and very much produced beyond the head in front.

The habits of this interesting mollusk are most singular, for it is found to live parasitically upon the animals of the class Echinodermata (Star-fishes and Sea-Urchins). Three species are known, one of which (Stylifer Turtoni) is a rare inhabitant of the British seas. Dr. Turton, however, its discoverer, found no fewer than a dozen attached to the spines of Echinus sphæra, dredged in Torbay. It has since been found in several localities, as on the coasts of Northumberland, Durham, and Cork, always under similar circumstances. Mr. Alder states, that it occurs on young Sea-Urchins.

A fine species was discovered in the Indian Archipelago by Mr. Hugh Cuming, and named S. astericola. He found this elegant parasite burrowing in different parts of the oral disc of Asterias solaris. It was almost hidden from sight, so deeply does the animal penetrate into the substance of the star-fish, in which it makes itself a comfortable cyst (or cell) for itself, and wherein it most probably turns by aid of its rudimentary foot. All the specimens infested with these testaceous mollusks appeared to be in the best health, though there is reason to believe that they feed upon the juices of the Star-fish. Mr. Broderip observes that Stylifer (with that instinct of self-preservation which is imparted to all parasites whose existence depends