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120 but is considered somewhat rare. It seems to be a deep water species: I have procured it by trawling off Portland. It is remarkable for a power possessed only in a very limited degree by any of the Mollusca, that of producing an audible sound.

Professor Grant, to whom we are indebted for a record of the curious fact, says "that the sounds resemble very much the clink of a steel wire on the side of the jar, one stroke only being given at a time, and repeated at intervals of a minute or two. When placed in a large basin of water, the sound is much obscured, and is like that of a watch, one stroke being repeated as before at intervals. The sound is longest and oftenest repeated when the Tritoniæ are lively and moving about, and is not heard when they are cold and without any motion. In the dark, I have not observed any light emitted at the time of the stroke; no globule of air escapes to the surface of the water, nor is any ripple produced on the surface at the instant of the stroke. The sound, when in a glass vessel, is mellow and distinct."

The Professor has kept these Tritoniæ alive in his room for a month; and during the whole period of their confinement, they have continued to produce the sounds, with very little diminution of their original intensity. In a still apartment, they are audible at the distance of twelve feet. "The sounds obviously proceed from the mouth of the animal, and at the instant of the stroke we observe the lips suddenly separate, as if to allow the water to rush into a small vacuum formed within. As these animals are hermaphrodites, requiring mutual impregnation, the sounds may possibly be a means of communication between them; or if