[337] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 93 



to a very large size in one season* it is evident that the best time to 

 take up the buoys would be in midsummer, before the early crop of 

 young have grown large, and leaving too little time for the later crop 

 to become large, in the buoys thus put down, before winter, when most 

 of them would probably be killed by the cold weather. In this way 

 the damage might be materially diminished, if not inconsistent with 

 the other duties of the officers of the vessels employed in this service. 

 There are, as yet, no means of estimating the extent of the damage 

 done to our wharves, shipping, &c., by this and the various other species 

 of Teredo found on onr coast, but judging from their abundance along 

 the whole coast, it is much greater than is generally supposed. 



The Teredo navalis is also abundant on the coast of Europe, from the 

 Mediterranean and Black Seas to Christiania, and the coasts of Great 

 Britain. Its habits have been quite thoroughly investigated by several 

 Dutch naturalists, owing to the great damage that it has done on their 

 coast, at times even threatening a general inundation of the country by 

 destroying the wood- work of the dikes. This Teredo occupies a zone 

 of considerable breadth, for it often lives considerably above low-water 

 mark and extends several feet below it, even to the depth of fourteen 

 feet, according to some writers. 



The best remedies in common use to resist or prevent its attacks are 

 copper-sheathing, used chiefly on vessels; broad-headed nails, closely 

 driven, used for piles and timbers; creosote and coal-tar, frequently applied. 

 The various poisonous substances that have been applied to timber for 

 this purpose, however useful they may be in other respects, have little 

 or no effect on the Teredo, for it does not depend upon the wood for its 

 food, and even protects its body externally with a layer of shell, lining 

 its holes. The only remedies that are likely to succeed are those calcu 

 lated to prevent the lodgment and entrance of the young ones beneath 

 the surface. Even creosote, thoroughly applied under pressure at the 

 rate of 10 pounds per square foot, has been found insufficient to prevent 

 their attacks, for piles thus treated at Christiania were found by Mr. 

 Jeffreys to be filled with the Teredo within two years after they were put 

 down. 



Several other species of Teredo also occur on this coast. The Teredo 

 megotara (Plate XXVII, fig. 188) has been found in floating pine wood at 

 Newport, Rhode Island, and in cedar buoys, &c., at New Bedford, 

 Massachusetts; as well as in Massachusetts Bay, at Provincetown and 

 other places ; it is also found as far south as South Carolina at least. 

 This species sometimes grows to a large size, forming tubes at least 

 eighteen inches long. It sometimes occurs, also, in the piles of wharves 

 in this region. The Teredo Thomsoni (Plate XXVII, fig. 187) has been 

 found in great numbers in the marine railway and also in cedar buoys 

 at New Bedford. It has also been found at Provincetown in a whaling- 

 ship that had cruised in the West Indies. 



The Xylotrya fimbriata (Plate XXVII, fig. 189) is very similar to the 



