. The economic mollusca of Acadia [microform]. Mollusks; Zoology, Economic; Mollusques; Zoologie économique. THE ECOXOMIC MOLLUSCA OF ACADIA. 109 that burled deepest in the wood, is tlie largeat. nnd nt its extremity \mirs tlie two valves, greatly reduced and forming the boring apparatus. Between them occurs the opening through which the slender •' foot " can be protuded, an organ correppondlnc with the "foot" in the (lam Except for this opening the mantle or " skin " of the animal is ;en until the posterior end is reached, where the body terminates in two tub
. The economic mollusca of Acadia [microform]. Mollusks; Zoology, Economic; Mollusques; Zoologie économique. THE ECOXOMIC MOLLUSCA OF ACADIA. 109 that burled deepest in the wood, is tlie largeat. nnd nt its extremity \mirs tlie two valves, greatly reduced and forming the boring apparatus. Between them occurs the opening through which the slender •' foot " can be protuded, an organ correppondlnc with the "foot" in the (lam Except for this opening the mantle or " skin " of the animal is ;en until the posterior end is reached, where the body terminates in two tubes or siphons, corresponding with those in the Clam. Probably one of these is for the admission of food and fresh water, and the other for the excr 'Ion of waste water and the wood which passes through the animal's body. These siphons can be retracted and the .,uite closed by two little calcareous valves or pallets, borne near the siphons. The latter, when the animal is distended, are at or near the surface of the wood. In burrowing, the Tmdo generally follows the grain of the wood but will cross it when necessary to avoid a knot, nail, neighbour's Fig. 22.— Teredo navalit. Twice Natural Size. or other obstruction. They never pierce each other's lubes. As the latter are formed, they are lined by a calcareous layer, more or less- thick, and firm enough to allow large pieces of it to be removed entire from the wood after the animal is dead. It is still doubtful what mechanism the animal employs in burrowing. Many nalura'ists think the valves, armed by numerous fine constantly growing teeth, form the apparatus, and that by them the animal eats, or rather flies its way onward. One observer states, that by breaking away the side of a burrow, he has actually seen this operation going on; others claim that the foot accomplishes the work, by the same unknown means by which, certain limpets can excavate rocks. It is pretty generally agreed, how- ever, that the Teredo
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectmollusks, bookyear188
