704 NATURAL H1STOEY OF AQUATIC ANIMALS. 



Teredo navalis, Linne". Cape Cod to Florida ; Sweden to Sicily. 



Teredo norvegica, Spengler. Cape Cod northward. 



Teredo megotara, Hanley. Massachusetts Bay to South Carolina. 



Teredo dilatata, Stimpson. Massachusetts to South Carolina. 



Teredo Thompson*, Tryon. Cape Cod, Massachusetts. 



Xylophaga dorsalis, Forbes and Hanley. North Atlantic. 



Xylotrya fimbriata, Jeffreys. Long Island Sound to Florida ; British Columbia; Europe. 



The most commonly observed of these is the Teredo navalis. This is the same species that has 

 attracted so much attention in Europe, during nearly two centuries, on account of the great 

 damage that it has done, especially on the coast of Holland. Its history has been reviewed at 

 length by Professor Verrill iu his " Invertebrates of Vineyard Sound," from which the present 

 account is principally derived. 



"Although popularly known as the 'Ship-worm,' these creatures are not at all related to the 

 worms, but are true mollusks, quite nearly allied, in many respects, to the common 'Long Clam' 

 (Mya) and to the Pholas. Like those shells, the Teredo excavates its holes or burrows merely for 

 its own protection, and not for food ; but the Teredo selects wood in which to form its holes, and 

 when these have been excavated it lines them with a tube of shelly material. The holes are very 

 small at the surface of the wood, where they were formed by the young Teredos, but they gradually 

 grow larger as they go deeper and deeper into the wood, until they sometimes become ten inches 

 or more iu length and a quarter of an inch iu diameter; but the size is generally not more than 

 half these dimensions. The holes penetrate the wood at first perpendicularly or obliquely, but if 

 they enter the side of the timbers or planks across the grain the burrows generally turn horizon- 

 tally in the direction of the grain a short distance beneath the surface, unless prevented by some 

 obstruction, or by the presence of other toredo tubes, for they never cross the tubes of their 

 companions or interfere with each other in any way, and there is always a thin layer or partition 

 of wood left between the adjacent tubes. It is, however, not necessary that they should follow 

 the grain of the wood, for they can and do penetrate it in every direction, and sometimes not more 

 than half the tubes run in the direction of the grain, and they are often very crooked or even 

 tortuous. They rapidly form their burrows in all kinds of our native woods, from the softest pine 

 to the hardest oak, and although they usually turn aside and go around hard knots, they are also 

 able to penetrate through even the hardest knots in oak and other hard woods. The Teredos 

 grow very rapidly, apparently attaining maturity in one season, and therefore, when abundant, 

 they may greatly damage or completely destroy small timber in the course of four or five months, 

 and even the largest piles may be destroyed by them in the course of two orthree years. 



" When removed from its tube the animal is found to have a very long, slender, smooth, soft, 

 whitish body, tapering somewhat toward the outer or posterior end, which has a muscular, circularly 

 wrinkled collar, by which the animal is, when living, attached to the inside of the shelly lining of 

 its tube. To the inside of this collar two shelly plates, known as the ' pallets,' are attached by 

 their slender basal prolongations; their outer portions are broad and flat, and more or less 

 emarginate or two-horned at the end. These are so connected with the muscles that when the 

 animal withdraws its tubes into its hole the free ends of these pallets are made to fold together 

 and close the opening, thus serving as an operculum to protect the soft tubes against enemies of 

 all kinds. Between the bases of the pallets arise the siphonal tubes, which are soft and retractile, 

 united together for half their length or more, but separate and divergent beyond ; they are nearly 

 equal, but the ventral or branchial tube is perhaps a little larger than the other, and is fringed 

 with a few small papillae at the end. The tubes are white or yellowish, sometimes speckled with 



