Page:Natural History, Mollusca.djvu/312
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DIMYARIA. — PHOLADIDÆ.
tion, about twenty inches long, the body of the animal has had no testaceous covering for the last three and a half inches; in two other cells, of about two feet, no deposition appears for four and a half, and four inches and three quarters from their termination. All the timber at Portpatrick in which the Teredo had formed its habitation, is pine, and perhaps to this circumstance the superior size of the animal may chiefly be attributed. Though it is well known that the Teredo bores in the direction of the grain, it may be observed that it does so whether the position of the wood be perpendicular or otherwise. Captan Fayrer remarked, that it has a decided disposition to work horizontally. It is, however, often obliged to deviate from a straightforward course, to avoid such obstructions as nails, timber-knots, and tubes of its fellows, and make a winding or angular habitation according as such impediments occur; but these circumstances seem not eventually to impede the progress of the animal, as some of the very largest specimens I have examined are the most tortuous. During the nine or ten years that the Teredo has been established at Portpatrick, it has not degenerated; as specimens just received, which were alive in their native element a few days ago, are of equal size to those sent from the same place live years since, showing that it has not been affected by the cold of the winter season, as we might reasonably expect were the animals truly exotic. If this animal had originally been introduced, and has been preserved only by occasional importations, should we not rather look for it in those parts of the United Kingdom where vessels from every quarter of the globe are congregated,